From: Denis Mukhin <dmukhin@ford.com>
Introduce a driver framework to abstract UART emulators in the hypervisor.
That allows for architecture-independent handling of virtual UARTs in the
console driver and simplifies enabling new UART emulators.
The framework is built under CONFIG_VUART_FRAMEWORK, which will be
automatically enabled once the user enables any UART emulator.
Current implementation supports maximum of one vUART of each kind per domain.
Use new domain_has_vuart() in the console driver code to check whether to
forward console input to the domain using vUART.
Enable console forwarding over vUART for hardware domains with a vUART. That
enables console forwarding to dom0 on x86, since console can be forwarded only
to Xen, dom0 and pvshim on x86 as of now.
Note: existing vUARTs are deliberately *not* hooked to the new framework to
minimize the scope of the patch: vpl011 (i.e. SBSA) emulator and "vuart" (i.e.
minimalistic MMIO-mapped dtuart for hwdoms on Arm) are kept unmodified.
No functional changes for non-x86 architectures.
Signed-off-by: Denis Mukhin <dmukhin@ford.com>
---
Changes since v4:
- addressed feedback
- Link to v4: https://lore.kernel.org/xen-devel/20250731192130.3948419-3-dmukhin@ford.com/
---
xen/arch/arm/xen.lds.S | 1 +
xen/arch/ppc/xen.lds.S | 1 +
xen/arch/riscv/xen.lds.S | 1 +
xen/arch/x86/xen.lds.S | 1 +
xen/common/Kconfig | 2 +
xen/common/Makefile | 1 +
xen/common/emul/Kconfig | 6 ++
xen/common/emul/Makefile | 1 +
xen/common/emul/vuart/Kconfig | 6 ++
xen/common/emul/vuart/Makefile | 1 +
xen/common/emul/vuart/vuart.c | 156 +++++++++++++++++++++++++++++++++
xen/common/keyhandler.c | 3 +
xen/drivers/char/console.c | 6 +-
xen/include/xen/serial.h | 3 +
xen/include/xen/vuart.h | 116 ++++++++++++++++++++++++
xen/include/xen/xen.lds.h | 10 +++
16 files changed, 314 insertions(+), 1 deletion(-)
create mode 100644 xen/common/emul/Kconfig
create mode 100644 xen/common/emul/Makefile
create mode 100644 xen/common/emul/vuart/Kconfig
create mode 100644 xen/common/emul/vuart/Makefile
create mode 100644 xen/common/emul/vuart/vuart.c
create mode 100644 xen/include/xen/vuart.h
diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index db17ff1efa98..cd05b18770f4 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -58,6 +58,7 @@ SECTIONS
*(.rodata)
*(.rodata.*)
VPCI_ARRAY
+ VUART_ARRAY
*(.data.rel.ro)
*(.data.rel.ro.*)
diff --git a/xen/arch/ppc/xen.lds.S b/xen/arch/ppc/xen.lds.S
index 1de0b77fc6b9..f9d4e5b0dcd8 100644
--- a/xen/arch/ppc/xen.lds.S
+++ b/xen/arch/ppc/xen.lds.S
@@ -52,6 +52,7 @@ SECTIONS
*(.rodata)
*(.rodata.*)
VPCI_ARRAY
+ VUART_ARRAY
*(.data.rel.ro)
*(.data.rel.ro.*)
diff --git a/xen/arch/riscv/xen.lds.S b/xen/arch/riscv/xen.lds.S
index edcadff90bfe..59dcaa5fef9a 100644
--- a/xen/arch/riscv/xen.lds.S
+++ b/xen/arch/riscv/xen.lds.S
@@ -47,6 +47,7 @@ SECTIONS
*(.rodata)
*(.rodata.*)
VPCI_ARRAY
+ VUART_ARRAY
*(.data.rel.ro)
*(.data.rel.ro.*)
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 966e514f2034..d877b93a6964 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -132,6 +132,7 @@ SECTIONS
*(.rodata)
*(.rodata.*)
VPCI_ARRAY
+ VUART_ARRAY
*(.data.rel.ro)
*(.data.rel.ro.*)
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index 76f9ce705f7a..78a32b69e2b2 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -676,4 +676,6 @@ config PM_STATS
Enable collection of performance management statistics to aid in
analyzing and tuning power/performance characteristics of the system
+source "common/emul/Kconfig"
+
endmenu
diff --git a/xen/common/Makefile b/xen/common/Makefile
index c316957fcb36..c0734480ee4b 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -11,6 +11,7 @@ obj-$(filter-out $(CONFIG_X86),$(CONFIG_ACPI)) += device.o
obj-$(CONFIG_DEVICE_TREE_PARSE) += device-tree/
obj-$(CONFIG_IOREQ_SERVER) += dm.o
obj-y += domain.o
+obj-y += emul/
obj-y += event_2l.o
obj-y += event_channel.o
obj-$(CONFIG_EVTCHN_FIFO) += event_fifo.o
diff --git a/xen/common/emul/Kconfig b/xen/common/emul/Kconfig
new file mode 100644
index 000000000000..7c6764d1756b
--- /dev/null
+++ b/xen/common/emul/Kconfig
@@ -0,0 +1,6 @@
+menu "Domain Emulation Features"
+ visible if EXPERT
+
+source "common/emul/vuart/Kconfig"
+
+endmenu
diff --git a/xen/common/emul/Makefile b/xen/common/emul/Makefile
new file mode 100644
index 000000000000..ae0b575c3901
--- /dev/null
+++ b/xen/common/emul/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_VUART_FRAMEWORK) += vuart/
diff --git a/xen/common/emul/vuart/Kconfig b/xen/common/emul/vuart/Kconfig
new file mode 100644
index 000000000000..ce1b976b7da7
--- /dev/null
+++ b/xen/common/emul/vuart/Kconfig
@@ -0,0 +1,6 @@
+config VUART_FRAMEWORK
+ bool
+
+menu "UART Emulation"
+
+endmenu
diff --git a/xen/common/emul/vuart/Makefile b/xen/common/emul/vuart/Makefile
new file mode 100644
index 000000000000..97f792dc6641
--- /dev/null
+++ b/xen/common/emul/vuart/Makefile
@@ -0,0 +1 @@
+obj-y += vuart.o
diff --git a/xen/common/emul/vuart/vuart.c b/xen/common/emul/vuart/vuart.c
new file mode 100644
index 000000000000..7b277d00d5c7
--- /dev/null
+++ b/xen/common/emul/vuart/vuart.c
@@ -0,0 +1,156 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * UART emulator framework.
+ *
+ * Copyright 2025 Ford Motor Company
+ */
+
+#include <xen/err.h>
+#include <xen/sched.h>
+#include <xen/vuart.h>
+#include <xen/xvmalloc.h>
+
+#define for_each_emulator(e) \
+ for ( e = vuart_array_start; e < vuart_array_end; e++ )
+
+extern const struct vuart_emulator vuart_array_start[];
+extern const struct vuart_emulator vuart_array_end[];
+
+static const struct vuart_emulator *
+vuart_match_by_compatible(struct domain *d, const char *compat)
+{
+ const struct vuart_emulator *emulator;
+
+ if ( d->console.vuart )
+ return NULL;
+
+ for_each_emulator(emulator)
+ if ( emulator->compatible &&
+ !strncmp(emulator->compatible, compat,
+ strlen(emulator->compatible)) )
+ return emulator;
+
+ return NULL;
+}
+
+static struct vuart *vuart_find_by_console_permission(const struct domain *d)
+{
+ struct vuart *vuart = d->console.vuart;
+
+ ASSERT(d->console.input_allowed);
+
+ if ( !vuart || !vuart->emulator || !vuart->emulator->put_rx ||
+ !(vuart->flags & VUART_CONSOLE_INPUT))
+ return NULL;
+
+ return vuart;
+}
+
+struct vuart *vuart_find_by_io_range(struct domain *d, unsigned long addr,
+ unsigned long size)
+{
+ struct vuart *vuart = d->console.vuart;
+
+ if ( !vuart || !vuart->info )
+ return NULL;
+
+ if ( addr >= vuart->info->base_addr &&
+ addr + size - 1 <= vuart->info->base_addr + vuart->info->size - 1 )
+ return vuart;
+
+ return NULL;
+}
+
+int vuart_init(struct domain *d, struct vuart_info *info)
+{
+ const struct vuart_emulator *emulator;
+ struct vuart *vuart;
+ int rc;
+
+ emulator = vuart_match_by_compatible(d, info->compatible);
+ if ( !emulator )
+ return -ENODEV;
+
+ vuart = xzalloc(typeof(*vuart));
+ if ( !vuart )
+ return -ENOMEM;
+
+ vuart->info = xvzalloc(typeof(*info));
+ if ( !vuart->info )
+ {
+ rc = -ENOMEM;
+ goto err_out;
+ }
+ memcpy(vuart->info, info, sizeof(*info));
+
+ vuart->vdev = emulator->alloc(d, vuart->info);
+ if ( IS_ERR(vuart->vdev) )
+ {
+ rc = PTR_ERR(vuart->vdev);
+ goto err_out;
+ }
+
+ vuart->emulator = emulator;
+ vuart->owner = d;
+ vuart->flags |= VUART_CONSOLE_INPUT;
+
+ d->console.input_allowed = true;
+ d->console.vuart = vuart;
+
+ return 0;
+
+ err_out:
+ XVFREE(vuart);
+ return rc;
+}
+
+/*
+ * Release any resources taken by UART emulators.
+ *
+ * NB: no flags are cleared, since currently exit() is called only during
+ * domain destroy.
+ */
+void vuart_deinit(struct domain *d)
+{
+ struct vuart *vuart = d->console.vuart;
+
+ if ( vuart )
+ {
+ vuart->emulator->free(vuart);
+ XVFREE(vuart->info);
+ }
+
+ XVFREE(d->console.vuart);
+}
+
+void vuart_dump_state(const struct domain *d)
+{
+ struct vuart *vuart = d->console.vuart;
+
+ if ( vuart )
+ vuart->emulator->dump_state(vuart);
+}
+
+/*
+ * Put character to the *first* suitable emulated UART's FIFO.
+ */
+int vuart_put_rx(struct domain *d, char c)
+{
+ struct vuart *vuart = vuart_find_by_console_permission(d);
+
+ return vuart ? vuart->emulator->put_rx(vuart, c) : -ENODEV;
+}
+
+bool domain_has_vuart(const struct domain *d)
+{
+ return vuart_find_by_console_permission(d);
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/common/keyhandler.c b/xen/common/keyhandler.c
index cb6df2823b00..156e64d9eb58 100644
--- a/xen/common/keyhandler.c
+++ b/xen/common/keyhandler.c
@@ -22,6 +22,7 @@
#include <xen/mm.h>
#include <xen/watchdog.h>
#include <xen/init.h>
+#include <xen/vuart.h>
#include <asm/div64.h>
static unsigned char keypress_key;
@@ -352,6 +353,8 @@ static void cf_check dump_domains(unsigned char key)
v->periodic_period / 1000000);
}
}
+
+ vuart_dump_state(d);
}
for_each_domain ( d )
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 9bd5b4825da6..d5164897a776 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -33,6 +33,7 @@
#include <asm/setup.h>
#include <xen/sections.h>
#include <xen/consoled.h>
+#include <xen/vuart.h>
#ifdef CONFIG_X86
#include <asm/guest.h>
@@ -596,11 +597,12 @@ static void __serial_rx(char c)
if ( !d )
return;
- if ( is_hardware_domain(d) )
+ if ( is_hardware_domain(d) && !domain_has_vuart(d) )
{
/*
* Deliver input to the hardware domain buffer, unless it is
* already full.
+ * NB: must be the first check: hardware domain may have emulated UART.
*/
if ( (serial_rx_prod - serial_rx_cons) != SERIAL_RX_SIZE )
serial_rx_ring[SERIAL_RX_MASK(serial_rx_prod++)] = c;
@@ -611,6 +613,8 @@ static void __serial_rx(char c)
*/
send_global_virq(VIRQ_CONSOLE);
}
+ else if ( domain_has_vuart(d) )
+ rc = vuart_put_rx(d, c);
#ifdef CONFIG_SBSA_VUART_CONSOLE
else
/* Deliver input to the emulated UART. */
diff --git a/xen/include/xen/serial.h b/xen/include/xen/serial.h
index 8e1844555208..d7e81f098359 100644
--- a/xen/include/xen/serial.h
+++ b/xen/include/xen/serial.h
@@ -36,6 +36,9 @@ struct vuart_info {
unsigned long data_off; /* Data register offset */
unsigned long status_off; /* Status register offset */
unsigned long status; /* Ready status value */
+ unsigned int irq; /* Interrupt */
+ const char *compatible; /* Compatible string */
+ const char *name; /* User-friendly name */
};
struct serial_port {
diff --git a/xen/include/xen/vuart.h b/xen/include/xen/vuart.h
new file mode 100644
index 000000000000..ca025b4179be
--- /dev/null
+++ b/xen/include/xen/vuart.h
@@ -0,0 +1,116 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * UART emulator framework.
+ *
+ * Copyright 2025 Ford Motor Company
+ */
+
+#ifndef XEN_VUART_H
+#define XEN_VUART_H
+
+#include <xen/serial.h>
+#include <public/xen.h>
+
+struct vuart_emulator;
+
+enum {
+ VUART_CONSOLE_INPUT = 0U << 1, /** Physical console input forwarding. */
+};
+
+
+/*
+ * FIXME: #ifdef is temporary to avoid clash with
+ * arch/arm/include/asm/domain.h
+ */
+#ifdef CONFIG_VUART_FRAMEWORK
+struct vuart {
+ const struct vuart_emulator *emulator;
+ struct vuart_info *info;
+ struct domain *owner;
+ uint32_t flags;
+ void *vdev;
+};
+#endif
+
+struct vuart_emulator {
+ /* UART compatible string. Cannot be NULL or empty. */
+ const char *compatible;
+
+ /*
+ * Allocate emulated UART state (RX/TX FIFOs, locks, initialize registers,
+ * hook I/O handlers, etc.)
+ * Cannot be NULL.
+ */
+ void *(*alloc)(struct domain *d, const struct vuart_info *info);
+
+ /*
+ * Release resources used to emulate UART state (flush RX/TX FIFOs, unhook
+ * I/O handlers, etc.).
+ * Cannot be NULL.
+ */
+ void (*free)(void *arg);
+
+ /*
+ * Print emulated UART state, including registers, on the console.
+ * Can be NULL.
+ */
+ void (*dump_state)(void *arg);
+
+ /*
+ * Place character to the emulated RX FIFO.
+ * Used to forward physical console input to the guest OS.
+ * Can be NULL.
+ */
+ int (*put_rx)(void *arg, char c);
+};
+
+#define VUART_REGISTER(name, x) \
+ static const struct vuart_emulator name##_entry \
+ __used_section(".data.rel.ro.vuart") = x
+
+struct vuart *vuart_find_by_io_range(struct domain *d,
+ unsigned long base_addr,
+ unsigned long size);
+
+int vuart_put_rx(struct domain *d, char c);
+
+#ifdef CONFIG_VUART_FRAMEWORK
+
+int vuart_init(struct domain *d, struct vuart_info *info);
+void vuart_deinit(struct domain *d);
+void vuart_dump_state(const struct domain *d);
+bool domain_has_vuart(const struct domain *d);
+
+#else
+
+static inline int vuart_init(struct domain *d, struct vuart_info *info)
+{
+ return 0;
+}
+
+static inline void vuart_deinit(struct domain *d)
+{
+}
+
+static inline void vuart_dump_state(const struct domain *d)
+{
+}
+
+static inline bool domain_has_vuart(const struct domain *d)
+{
+ return false;
+}
+
+#endif /* CONFIG_VUART_FRAMEWORK */
+
+#endif /* XEN_VUART_H */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
+
diff --git a/xen/include/xen/xen.lds.h b/xen/include/xen/xen.lds.h
index b126dfe88792..2d65f32ddad3 100644
--- a/xen/include/xen/xen.lds.h
+++ b/xen/include/xen/xen.lds.h
@@ -194,4 +194,14 @@
#define VPCI_ARRAY
#endif
+#ifdef CONFIG_VUART_FRAMEWORK
+#define VUART_ARRAY \
+ . = ALIGN(POINTER_ALIGN); \
+ vuart_array_start = .; \
+ *(.data.rel.ro.vuart) \
+ vuart_array_end = .;
+#else
+#define VUART_ARRAY
+#endif
+
#endif /* __XEN_LDS_H__ */
--
2.51.0On Thu, 28 Aug 2025, dmukhin@xen.org wrote:
> From: Denis Mukhin <dmukhin@ford.com>
>
> Introduce a driver framework to abstract UART emulators in the hypervisor.
>
> That allows for architecture-independent handling of virtual UARTs in the
> console driver and simplifies enabling new UART emulators.
>
> The framework is built under CONFIG_VUART_FRAMEWORK, which will be
> automatically enabled once the user enables any UART emulator.
>
> Current implementation supports maximum of one vUART of each kind per domain.
>
> Use new domain_has_vuart() in the console driver code to check whether to
> forward console input to the domain using vUART.
>
> Enable console forwarding over vUART for hardware domains with a vUART. That
> enables console forwarding to dom0 on x86, since console can be forwarded only
> to Xen, dom0 and pvshim on x86 as of now.
>
> Note: existing vUARTs are deliberately *not* hooked to the new framework to
> minimize the scope of the patch: vpl011 (i.e. SBSA) emulator and "vuart" (i.e.
> minimalistic MMIO-mapped dtuart for hwdoms on Arm) are kept unmodified.
>
> No functional changes for non-x86 architectures.
>
> Signed-off-by: Denis Mukhin <dmukhin@ford.com>
> ---
> Changes since v4:
> - addressed feedback
> - Link to v4: https://lore.kernel.org/xen-devel/20250731192130.3948419-3-dmukhin@ford.com/
> ---
> xen/arch/arm/xen.lds.S | 1 +
> xen/arch/ppc/xen.lds.S | 1 +
> xen/arch/riscv/xen.lds.S | 1 +
> xen/arch/x86/xen.lds.S | 1 +
> xen/common/Kconfig | 2 +
> xen/common/Makefile | 1 +
> xen/common/emul/Kconfig | 6 ++
> xen/common/emul/Makefile | 1 +
> xen/common/emul/vuart/Kconfig | 6 ++
> xen/common/emul/vuart/Makefile | 1 +
> xen/common/emul/vuart/vuart.c | 156 +++++++++++++++++++++++++++++++++
> xen/common/keyhandler.c | 3 +
> xen/drivers/char/console.c | 6 +-
> xen/include/xen/serial.h | 3 +
> xen/include/xen/vuart.h | 116 ++++++++++++++++++++++++
> xen/include/xen/xen.lds.h | 10 +++
> 16 files changed, 314 insertions(+), 1 deletion(-)
> create mode 100644 xen/common/emul/Kconfig
> create mode 100644 xen/common/emul/Makefile
> create mode 100644 xen/common/emul/vuart/Kconfig
> create mode 100644 xen/common/emul/vuart/Makefile
> create mode 100644 xen/common/emul/vuart/vuart.c
> create mode 100644 xen/include/xen/vuart.h
>
> diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
> index db17ff1efa98..cd05b18770f4 100644
> --- a/xen/arch/arm/xen.lds.S
> +++ b/xen/arch/arm/xen.lds.S
> @@ -58,6 +58,7 @@ SECTIONS
> *(.rodata)
> *(.rodata.*)
> VPCI_ARRAY
> + VUART_ARRAY
> *(.data.rel.ro)
> *(.data.rel.ro.*)
>
> diff --git a/xen/arch/ppc/xen.lds.S b/xen/arch/ppc/xen.lds.S
> index 1de0b77fc6b9..f9d4e5b0dcd8 100644
> --- a/xen/arch/ppc/xen.lds.S
> +++ b/xen/arch/ppc/xen.lds.S
> @@ -52,6 +52,7 @@ SECTIONS
> *(.rodata)
> *(.rodata.*)
> VPCI_ARRAY
> + VUART_ARRAY
> *(.data.rel.ro)
> *(.data.rel.ro.*)
>
> diff --git a/xen/arch/riscv/xen.lds.S b/xen/arch/riscv/xen.lds.S
> index edcadff90bfe..59dcaa5fef9a 100644
> --- a/xen/arch/riscv/xen.lds.S
> +++ b/xen/arch/riscv/xen.lds.S
> @@ -47,6 +47,7 @@ SECTIONS
> *(.rodata)
> *(.rodata.*)
> VPCI_ARRAY
> + VUART_ARRAY
> *(.data.rel.ro)
> *(.data.rel.ro.*)
>
> diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
> index 966e514f2034..d877b93a6964 100644
> --- a/xen/arch/x86/xen.lds.S
> +++ b/xen/arch/x86/xen.lds.S
> @@ -132,6 +132,7 @@ SECTIONS
> *(.rodata)
> *(.rodata.*)
> VPCI_ARRAY
> + VUART_ARRAY
> *(.data.rel.ro)
> *(.data.rel.ro.*)
>
> diff --git a/xen/common/Kconfig b/xen/common/Kconfig
> index 76f9ce705f7a..78a32b69e2b2 100644
> --- a/xen/common/Kconfig
> +++ b/xen/common/Kconfig
> @@ -676,4 +676,6 @@ config PM_STATS
> Enable collection of performance management statistics to aid in
> analyzing and tuning power/performance characteristics of the system
>
> +source "common/emul/Kconfig"
> +
> endmenu
> diff --git a/xen/common/Makefile b/xen/common/Makefile
> index c316957fcb36..c0734480ee4b 100644
> --- a/xen/common/Makefile
> +++ b/xen/common/Makefile
> @@ -11,6 +11,7 @@ obj-$(filter-out $(CONFIG_X86),$(CONFIG_ACPI)) += device.o
> obj-$(CONFIG_DEVICE_TREE_PARSE) += device-tree/
> obj-$(CONFIG_IOREQ_SERVER) += dm.o
> obj-y += domain.o
> +obj-y += emul/
> obj-y += event_2l.o
> obj-y += event_channel.o
> obj-$(CONFIG_EVTCHN_FIFO) += event_fifo.o
> diff --git a/xen/common/emul/Kconfig b/xen/common/emul/Kconfig
> new file mode 100644
> index 000000000000..7c6764d1756b
> --- /dev/null
> +++ b/xen/common/emul/Kconfig
> @@ -0,0 +1,6 @@
> +menu "Domain Emulation Features"
> + visible if EXPERT
> +
> +source "common/emul/vuart/Kconfig"
> +
> +endmenu
> diff --git a/xen/common/emul/Makefile b/xen/common/emul/Makefile
> new file mode 100644
> index 000000000000..ae0b575c3901
> --- /dev/null
> +++ b/xen/common/emul/Makefile
> @@ -0,0 +1 @@
> +obj-$(CONFIG_VUART_FRAMEWORK) += vuart/
> diff --git a/xen/common/emul/vuart/Kconfig b/xen/common/emul/vuart/Kconfig
> new file mode 100644
> index 000000000000..ce1b976b7da7
> --- /dev/null
> +++ b/xen/common/emul/vuart/Kconfig
> @@ -0,0 +1,6 @@
> +config VUART_FRAMEWORK
> + bool
> +
> +menu "UART Emulation"
> +
> +endmenu
> diff --git a/xen/common/emul/vuart/Makefile b/xen/common/emul/vuart/Makefile
> new file mode 100644
> index 000000000000..97f792dc6641
> --- /dev/null
> +++ b/xen/common/emul/vuart/Makefile
> @@ -0,0 +1 @@
> +obj-y += vuart.o
> diff --git a/xen/common/emul/vuart/vuart.c b/xen/common/emul/vuart/vuart.c
> new file mode 100644
> index 000000000000..7b277d00d5c7
> --- /dev/null
> +++ b/xen/common/emul/vuart/vuart.c
> @@ -0,0 +1,156 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * UART emulator framework.
> + *
> + * Copyright 2025 Ford Motor Company
> + */
> +
> +#include <xen/err.h>
> +#include <xen/sched.h>
> +#include <xen/vuart.h>
> +#include <xen/xvmalloc.h>
> +
> +#define for_each_emulator(e) \
> + for ( e = vuart_array_start; e < vuart_array_end; e++ )
> +
> +extern const struct vuart_emulator vuart_array_start[];
> +extern const struct vuart_emulator vuart_array_end[];
> +
> +static const struct vuart_emulator *
> +vuart_match_by_compatible(struct domain *d, const char *compat)
> +{
> + const struct vuart_emulator *emulator;
> +
> + if ( d->console.vuart )
> + return NULL;
> +
> + for_each_emulator(emulator)
> + if ( emulator->compatible &&
> + !strncmp(emulator->compatible, compat,
> + strlen(emulator->compatible)) )
strncmp will continue until the given count even if compat is shorter
> + return emulator;
> +
> + return NULL;
> +}
> +
> +static struct vuart *vuart_find_by_console_permission(const struct domain *d)
> +{
> + struct vuart *vuart = d->console.vuart;
> +
> + ASSERT(d->console.input_allowed);
This ASSERT looks suspicious as we haven't even checked that vuart!=NULL
yet. I would remove it
> + if ( !vuart || !vuart->emulator || !vuart->emulator->put_rx ||
> + !(vuart->flags & VUART_CONSOLE_INPUT))
> + return NULL;
> +
> + return vuart;
> +}
> +
> +struct vuart *vuart_find_by_io_range(struct domain *d, unsigned long addr,
> + unsigned long size)
> +{
> + struct vuart *vuart = d->console.vuart;
> +
> + if ( !vuart || !vuart->info )
> + return NULL;
You might as well call vuart_find_by_console_permission that has all the
checks already
> +
> + if ( addr >= vuart->info->base_addr &&
> + addr + size - 1 <= vuart->info->base_addr + vuart->info->size - 1 )
> + return vuart;
> +
> + return NULL;
> +}
> +
> +int vuart_init(struct domain *d, struct vuart_info *info)
> +{
> + const struct vuart_emulator *emulator;
> + struct vuart *vuart;
> + int rc;
> +
> + emulator = vuart_match_by_compatible(d, info->compatible);
> + if ( !emulator )
> + return -ENODEV;
> +
> + vuart = xzalloc(typeof(*vuart));
> + if ( !vuart )
> + return -ENOMEM;
> +
> + vuart->info = xvzalloc(typeof(*info));
> + if ( !vuart->info )
> + {
> + rc = -ENOMEM;
> + goto err_out;
> + }
> + memcpy(vuart->info, info, sizeof(*info));
one thing to note is that the fields (strings) compatible and name are
copied by address, I am not if it is OK but FYI
> + vuart->vdev = emulator->alloc(d, vuart->info);
> + if ( IS_ERR(vuart->vdev) )
> + {
> + rc = PTR_ERR(vuart->vdev);
> + goto err_out;
this path leads to vuart->info not being freed
> + }
> +
> + vuart->emulator = emulator;
> + vuart->owner = d;
> + vuart->flags |= VUART_CONSOLE_INPUT;
> +
> + d->console.input_allowed = true;
> + d->console.vuart = vuart;
> +
> + return 0;
> +
> + err_out:
> + XVFREE(vuart);
> + return rc;
> +}
> +
> +/*
> + * Release any resources taken by UART emulators.
> + *
> + * NB: no flags are cleared, since currently exit() is called only during
> + * domain destroy.
> + */
> +void vuart_deinit(struct domain *d)
> +{
> + struct vuart *vuart = d->console.vuart;
> +
> + if ( vuart )
> + {
> + vuart->emulator->free(vuart);
should we pass vuart or vuart->vdev here? The emulator state is supposed
to be vuart->vdev?
> + XVFREE(vuart->info);
> + }
> +
> + XVFREE(d->console.vuart);
> +}
> +
> +void vuart_dump_state(const struct domain *d)
> +{
> + struct vuart *vuart = d->console.vuart;
> +
> + if ( vuart )
> + vuart->emulator->dump_state(vuart);
also here vuart->vdev?
> +}
> +
> +/*
> + * Put character to the *first* suitable emulated UART's FIFO.
> + */
> +int vuart_put_rx(struct domain *d, char c)
> +{
> + struct vuart *vuart = vuart_find_by_console_permission(d);
> +
> + return vuart ? vuart->emulator->put_rx(vuart, c) : -ENODEV;
and here?
> +}
> +
> +bool domain_has_vuart(const struct domain *d)
> +{
> + return vuart_find_by_console_permission(d);
> +}
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> diff --git a/xen/common/keyhandler.c b/xen/common/keyhandler.c
> index cb6df2823b00..156e64d9eb58 100644
> --- a/xen/common/keyhandler.c
> +++ b/xen/common/keyhandler.c
> @@ -22,6 +22,7 @@
> #include <xen/mm.h>
> #include <xen/watchdog.h>
> #include <xen/init.h>
> +#include <xen/vuart.h>
> #include <asm/div64.h>
>
> static unsigned char keypress_key;
> @@ -352,6 +353,8 @@ static void cf_check dump_domains(unsigned char key)
> v->periodic_period / 1000000);
> }
> }
> +
> + vuart_dump_state(d);
> }
>
> for_each_domain ( d )
> diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
> index 9bd5b4825da6..d5164897a776 100644
> --- a/xen/drivers/char/console.c
> +++ b/xen/drivers/char/console.c
> @@ -33,6 +33,7 @@
> #include <asm/setup.h>
> #include <xen/sections.h>
> #include <xen/consoled.h>
> +#include <xen/vuart.h>
>
> #ifdef CONFIG_X86
> #include <asm/guest.h>
> @@ -596,11 +597,12 @@ static void __serial_rx(char c)
> if ( !d )
> return;
>
> - if ( is_hardware_domain(d) )
> + if ( is_hardware_domain(d) && !domain_has_vuart(d) )
> {
> /*
> * Deliver input to the hardware domain buffer, unless it is
> * already full.
> + * NB: must be the first check: hardware domain may have emulated UART.
> */
> if ( (serial_rx_prod - serial_rx_cons) != SERIAL_RX_SIZE )
> serial_rx_ring[SERIAL_RX_MASK(serial_rx_prod++)] = c;
> @@ -611,6 +613,8 @@ static void __serial_rx(char c)
> */
> send_global_virq(VIRQ_CONSOLE);
> }
> + else if ( domain_has_vuart(d) )
> + rc = vuart_put_rx(d, c);
> #ifdef CONFIG_SBSA_VUART_CONSOLE
> else
> /* Deliver input to the emulated UART. */
> diff --git a/xen/include/xen/serial.h b/xen/include/xen/serial.h
> index 8e1844555208..d7e81f098359 100644
> --- a/xen/include/xen/serial.h
> +++ b/xen/include/xen/serial.h
> @@ -36,6 +36,9 @@ struct vuart_info {
> unsigned long data_off; /* Data register offset */
> unsigned long status_off; /* Status register offset */
> unsigned long status; /* Ready status value */
> + unsigned int irq; /* Interrupt */
> + const char *compatible; /* Compatible string */
> + const char *name; /* User-friendly name */
> };
>
> struct serial_port {
> diff --git a/xen/include/xen/vuart.h b/xen/include/xen/vuart.h
> new file mode 100644
> index 000000000000..ca025b4179be
> --- /dev/null
> +++ b/xen/include/xen/vuart.h
> @@ -0,0 +1,116 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * UART emulator framework.
> + *
> + * Copyright 2025 Ford Motor Company
> + */
> +
> +#ifndef XEN_VUART_H
> +#define XEN_VUART_H
> +
> +#include <xen/serial.h>
> +#include <public/xen.h>
> +
> +struct vuart_emulator;
> +
> +enum {
> + VUART_CONSOLE_INPUT = 0U << 1, /** Physical console input forwarding. */
code style: single *
This flag is zero, is that intended?
> +};
> +
> +
> +/*
> + * FIXME: #ifdef is temporary to avoid clash with
> + * arch/arm/include/asm/domain.h
> + */
> +#ifdef CONFIG_VUART_FRAMEWORK
> +struct vuart {
> + const struct vuart_emulator *emulator;
> + struct vuart_info *info;
> + struct domain *owner;
> + uint32_t flags;
> + void *vdev;
> +};
> +#endif
> +
> +struct vuart_emulator {
> + /* UART compatible string. Cannot be NULL or empty. */
> + const char *compatible;
> +
> + /*
> + * Allocate emulated UART state (RX/TX FIFOs, locks, initialize registers,
> + * hook I/O handlers, etc.)
> + * Cannot be NULL.
> + */
> + void *(*alloc)(struct domain *d, const struct vuart_info *info);
> +
> + /*
> + * Release resources used to emulate UART state (flush RX/TX FIFOs, unhook
> + * I/O handlers, etc.).
> + * Cannot be NULL.
> + */
> + void (*free)(void *arg);
> +
> + /*
> + * Print emulated UART state, including registers, on the console.
> + * Can be NULL.
> + */
> + void (*dump_state)(void *arg);
> +
> + /*
> + * Place character to the emulated RX FIFO.
> + * Used to forward physical console input to the guest OS.
> + * Can be NULL.
> + */
> + int (*put_rx)(void *arg, char c);
> +};
> +
> +#define VUART_REGISTER(name, x) \
> + static const struct vuart_emulator name##_entry \
> + __used_section(".data.rel.ro.vuart") = x
> +
> +struct vuart *vuart_find_by_io_range(struct domain *d,
> + unsigned long base_addr,
> + unsigned long size);
> +
> +int vuart_put_rx(struct domain *d, char c);
> +
> +#ifdef CONFIG_VUART_FRAMEWORK
> +
> +int vuart_init(struct domain *d, struct vuart_info *info);
> +void vuart_deinit(struct domain *d);
> +void vuart_dump_state(const struct domain *d);
> +bool domain_has_vuart(const struct domain *d);
> +
> +#else
> +
> +static inline int vuart_init(struct domain *d, struct vuart_info *info)
> +{
> + return 0;
> +}
> +
> +static inline void vuart_deinit(struct domain *d)
> +{
> +}
> +
> +static inline void vuart_dump_state(const struct domain *d)
> +{
> +}
> +
> +static inline bool domain_has_vuart(const struct domain *d)
> +{
> + return false;
> +}
> +
> +#endif /* CONFIG_VUART_FRAMEWORK */
> +
> +#endif /* XEN_VUART_H */
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> +
> diff --git a/xen/include/xen/xen.lds.h b/xen/include/xen/xen.lds.h
> index b126dfe88792..2d65f32ddad3 100644
> --- a/xen/include/xen/xen.lds.h
> +++ b/xen/include/xen/xen.lds.h
> @@ -194,4 +194,14 @@
> #define VPCI_ARRAY
> #endif
>
> +#ifdef CONFIG_VUART_FRAMEWORK
> +#define VUART_ARRAY \
> + . = ALIGN(POINTER_ALIGN); \
> + vuart_array_start = .; \
> + *(.data.rel.ro.vuart) \
> + vuart_array_end = .;
> +#else
> +#define VUART_ARRAY
> +#endif
> +
> #endif /* __XEN_LDS_H__ */
> --
> 2.51.0
>
On Fri, Aug 29, 2025 at 12:27:13PM -0700, Stefano Stabellini wrote:
> On Thu, 28 Aug 2025, dmukhin@xen.org wrote:
> > From: Denis Mukhin <dmukhin@ford.com>
> >
> > Introduce a driver framework to abstract UART emulators in the hypervisor.
> >
> > That allows for architecture-independent handling of virtual UARTs in the
> > console driver and simplifies enabling new UART emulators.
> >
> > The framework is built under CONFIG_VUART_FRAMEWORK, which will be
> > automatically enabled once the user enables any UART emulator.
> >
> > Current implementation supports maximum of one vUART of each kind per domain.
> >
> > Use new domain_has_vuart() in the console driver code to check whether to
> > forward console input to the domain using vUART.
> >
> > Enable console forwarding over vUART for hardware domains with a vUART. That
> > enables console forwarding to dom0 on x86, since console can be forwarded only
> > to Xen, dom0 and pvshim on x86 as of now.
> >
> > Note: existing vUARTs are deliberately *not* hooked to the new framework to
> > minimize the scope of the patch: vpl011 (i.e. SBSA) emulator and "vuart" (i.e.
> > minimalistic MMIO-mapped dtuart for hwdoms on Arm) are kept unmodified.
> >
> > No functional changes for non-x86 architectures.
> >
> > Signed-off-by: Denis Mukhin <dmukhin@ford.com>
> > ---
> > Changes since v4:
> > - addressed feedback
> > - Link to v4: https://lore.kernel.org/xen-devel/20250731192130.3948419-3-dmukhin@ford.com/
> > ---
> > xen/arch/arm/xen.lds.S | 1 +
> > xen/arch/ppc/xen.lds.S | 1 +
> > xen/arch/riscv/xen.lds.S | 1 +
> > xen/arch/x86/xen.lds.S | 1 +
> > xen/common/Kconfig | 2 +
> > xen/common/Makefile | 1 +
> > xen/common/emul/Kconfig | 6 ++
> > xen/common/emul/Makefile | 1 +
> > xen/common/emul/vuart/Kconfig | 6 ++
> > xen/common/emul/vuart/Makefile | 1 +
> > xen/common/emul/vuart/vuart.c | 156 +++++++++++++++++++++++++++++++++
> > xen/common/keyhandler.c | 3 +
> > xen/drivers/char/console.c | 6 +-
> > xen/include/xen/serial.h | 3 +
> > xen/include/xen/vuart.h | 116 ++++++++++++++++++++++++
> > xen/include/xen/xen.lds.h | 10 +++
> > 16 files changed, 314 insertions(+), 1 deletion(-)
> > create mode 100644 xen/common/emul/Kconfig
> > create mode 100644 xen/common/emul/Makefile
> > create mode 100644 xen/common/emul/vuart/Kconfig
> > create mode 100644 xen/common/emul/vuart/Makefile
> > create mode 100644 xen/common/emul/vuart/vuart.c
> > create mode 100644 xen/include/xen/vuart.h
> >
> > diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
> > index db17ff1efa98..cd05b18770f4 100644
> > --- a/xen/arch/arm/xen.lds.S
> > +++ b/xen/arch/arm/xen.lds.S
> > @@ -58,6 +58,7 @@ SECTIONS
> > *(.rodata)
> > *(.rodata.*)
> > VPCI_ARRAY
> > + VUART_ARRAY
> > *(.data.rel.ro)
> > *(.data.rel.ro.*)
> >
> > diff --git a/xen/arch/ppc/xen.lds.S b/xen/arch/ppc/xen.lds.S
> > index 1de0b77fc6b9..f9d4e5b0dcd8 100644
> > --- a/xen/arch/ppc/xen.lds.S
> > +++ b/xen/arch/ppc/xen.lds.S
> > @@ -52,6 +52,7 @@ SECTIONS
> > *(.rodata)
> > *(.rodata.*)
> > VPCI_ARRAY
> > + VUART_ARRAY
> > *(.data.rel.ro)
> > *(.data.rel.ro.*)
> >
> > diff --git a/xen/arch/riscv/xen.lds.S b/xen/arch/riscv/xen.lds.S
> > index edcadff90bfe..59dcaa5fef9a 100644
> > --- a/xen/arch/riscv/xen.lds.S
> > +++ b/xen/arch/riscv/xen.lds.S
> > @@ -47,6 +47,7 @@ SECTIONS
> > *(.rodata)
> > *(.rodata.*)
> > VPCI_ARRAY
> > + VUART_ARRAY
> > *(.data.rel.ro)
> > *(.data.rel.ro.*)
> >
> > diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
> > index 966e514f2034..d877b93a6964 100644
> > --- a/xen/arch/x86/xen.lds.S
> > +++ b/xen/arch/x86/xen.lds.S
> > @@ -132,6 +132,7 @@ SECTIONS
> > *(.rodata)
> > *(.rodata.*)
> > VPCI_ARRAY
> > + VUART_ARRAY
> > *(.data.rel.ro)
> > *(.data.rel.ro.*)
> >
> > diff --git a/xen/common/Kconfig b/xen/common/Kconfig
> > index 76f9ce705f7a..78a32b69e2b2 100644
> > --- a/xen/common/Kconfig
> > +++ b/xen/common/Kconfig
> > @@ -676,4 +676,6 @@ config PM_STATS
> > Enable collection of performance management statistics to aid in
> > analyzing and tuning power/performance characteristics of the system
> >
> > +source "common/emul/Kconfig"
> > +
> > endmenu
> > diff --git a/xen/common/Makefile b/xen/common/Makefile
> > index c316957fcb36..c0734480ee4b 100644
> > --- a/xen/common/Makefile
> > +++ b/xen/common/Makefile
> > @@ -11,6 +11,7 @@ obj-$(filter-out $(CONFIG_X86),$(CONFIG_ACPI)) += device.o
> > obj-$(CONFIG_DEVICE_TREE_PARSE) += device-tree/
> > obj-$(CONFIG_IOREQ_SERVER) += dm.o
> > obj-y += domain.o
> > +obj-y += emul/
> > obj-y += event_2l.o
> > obj-y += event_channel.o
> > obj-$(CONFIG_EVTCHN_FIFO) += event_fifo.o
> > diff --git a/xen/common/emul/Kconfig b/xen/common/emul/Kconfig
> > new file mode 100644
> > index 000000000000..7c6764d1756b
> > --- /dev/null
> > +++ b/xen/common/emul/Kconfig
> > @@ -0,0 +1,6 @@
> > +menu "Domain Emulation Features"
> > + visible if EXPERT
> > +
> > +source "common/emul/vuart/Kconfig"
> > +
> > +endmenu
> > diff --git a/xen/common/emul/Makefile b/xen/common/emul/Makefile
> > new file mode 100644
> > index 000000000000..ae0b575c3901
> > --- /dev/null
> > +++ b/xen/common/emul/Makefile
> > @@ -0,0 +1 @@
> > +obj-$(CONFIG_VUART_FRAMEWORK) += vuart/
> > diff --git a/xen/common/emul/vuart/Kconfig b/xen/common/emul/vuart/Kconfig
> > new file mode 100644
> > index 000000000000..ce1b976b7da7
> > --- /dev/null
> > +++ b/xen/common/emul/vuart/Kconfig
> > @@ -0,0 +1,6 @@
> > +config VUART_FRAMEWORK
> > + bool
> > +
> > +menu "UART Emulation"
> > +
> > +endmenu
> > diff --git a/xen/common/emul/vuart/Makefile b/xen/common/emul/vuart/Makefile
> > new file mode 100644
> > index 000000000000..97f792dc6641
> > --- /dev/null
> > +++ b/xen/common/emul/vuart/Makefile
> > @@ -0,0 +1 @@
> > +obj-y += vuart.o
> > diff --git a/xen/common/emul/vuart/vuart.c b/xen/common/emul/vuart/vuart.c
> > new file mode 100644
> > index 000000000000..7b277d00d5c7
> > --- /dev/null
> > +++ b/xen/common/emul/vuart/vuart.c
> > @@ -0,0 +1,156 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * UART emulator framework.
> > + *
> > + * Copyright 2025 Ford Motor Company
> > + */
> > +
> > +#include <xen/err.h>
> > +#include <xen/sched.h>
> > +#include <xen/vuart.h>
> > +#include <xen/xvmalloc.h>
> > +
> > +#define for_each_emulator(e) \
> > + for ( e = vuart_array_start; e < vuart_array_end; e++ )
> > +
> > +extern const struct vuart_emulator vuart_array_start[];
> > +extern const struct vuart_emulator vuart_array_end[];
> > +
> > +static const struct vuart_emulator *
> > +vuart_match_by_compatible(struct domain *d, const char *compat)
> > +{
> > + const struct vuart_emulator *emulator;
> > +
> > + if ( d->console.vuart )
> > + return NULL;
> > +
> > + for_each_emulator(emulator)
> > + if ( emulator->compatible &&
> > + !strncmp(emulator->compatible, compat,
> > + strlen(emulator->compatible)) )
>
> strncmp will continue until the given count even if compat is shorter
I checked lib/strncmp.c. I'll flip the arguments, so that strncmp() will
return early if compat is shorter than emulator->compatible
>
>
> > + return emulator;
> > +
> > + return NULL;
> > +}
> > +
> > +static struct vuart *vuart_find_by_console_permission(const struct domain *d)
> > +{
> > + struct vuart *vuart = d->console.vuart;
> > +
> > + ASSERT(d->console.input_allowed);
>
> This ASSERT looks suspicious as we haven't even checked that vuart!=NULL
> yet. I would remove it
Ack
>
>
> > + if ( !vuart || !vuart->emulator || !vuart->emulator->put_rx ||
> > + !(vuart->flags & VUART_CONSOLE_INPUT))
> > + return NULL;
> > +
> > + return vuart;
> > +}
> > +
> > +struct vuart *vuart_find_by_io_range(struct domain *d, unsigned long addr,
> > + unsigned long size)
> > +{
> > + struct vuart *vuart = d->console.vuart;
> > +
> > + if ( !vuart || !vuart->info )
> > + return NULL;
>
> You might as well call vuart_find_by_console_permission that has all the
> checks already
vuart_find_by_io_range() is used in the I/O hook to find the vUART by its
I/O port range.
Using vuart_find_by_console_permission() here may be problematic if the
vUART does not support/enable console forwarding.
I'll keep this check as is for now.
>
> > +
> > + if ( addr >= vuart->info->base_addr &&
> > + addr + size - 1 <= vuart->info->base_addr + vuart->info->size - 1 )
> > + return vuart;
> > +
> > + return NULL;
> > +}
> > +
> > +int vuart_init(struct domain *d, struct vuart_info *info)
> > +{
> > + const struct vuart_emulator *emulator;
> > + struct vuart *vuart;
> > + int rc;
> > +
> > + emulator = vuart_match_by_compatible(d, info->compatible);
> > + if ( !emulator )
> > + return -ENODEV;
> > +
> > + vuart = xzalloc(typeof(*vuart));
> > + if ( !vuart )
> > + return -ENOMEM;
> > +
> > + vuart->info = xvzalloc(typeof(*info));
> > + if ( !vuart->info )
> > + {
> > + rc = -ENOMEM;
> > + goto err_out;
> > + }
> > + memcpy(vuart->info, info, sizeof(*info));
>
> one thing to note is that the fields (strings) compatible and name are
> copied by address, I am not if it is OK but FYI
Thanks, will update vuart_info struct.
>
>
> > + vuart->vdev = emulator->alloc(d, vuart->info);
> > + if ( IS_ERR(vuart->vdev) )
> > + {
> > + rc = PTR_ERR(vuart->vdev);
> > + goto err_out;
>
> this path leads to vuart->info not being freed
Thanks
>
>
> > + }
> > +
> > + vuart->emulator = emulator;
> > + vuart->owner = d;
> > + vuart->flags |= VUART_CONSOLE_INPUT;
> > +
> > + d->console.input_allowed = true;
> > + d->console.vuart = vuart;
> > +
> > + return 0;
> > +
> > + err_out:
> > + XVFREE(vuart);
> > + return rc;
> > +}
> > +
> > +/*
> > + * Release any resources taken by UART emulators.
> > + *
> > + * NB: no flags are cleared, since currently exit() is called only during
> > + * domain destroy.
> > + */
> > +void vuart_deinit(struct domain *d)
> > +{
> > + struct vuart *vuart = d->console.vuart;
> > +
> > + if ( vuart )
> > + {
> > + vuart->emulator->free(vuart);
>
> should we pass vuart or vuart->vdev here? The emulator state is supposed
> to be vuart->vdev?
That should be vuart->vdev; thanks!
>
> > + XVFREE(vuart->info);
> > + }
> > +
> > + XVFREE(d->console.vuart);
> > +}
> > +
> > +void vuart_dump_state(const struct domain *d)
> > +{
> > + struct vuart *vuart = d->console.vuart;
> > +
> > + if ( vuart )
> > + vuart->emulator->dump_state(vuart);
>
> also here vuart->vdev?
Ack
>
>
> > +}
> > +
> > +/*
> > + * Put character to the *first* suitable emulated UART's FIFO.
> > + */
> > +int vuart_put_rx(struct domain *d, char c)
> > +{
> > + struct vuart *vuart = vuart_find_by_console_permission(d);
> > +
> > + return vuart ? vuart->emulator->put_rx(vuart, c) : -ENODEV;
>
> and here?
Ack
>
>
> > +}
> > +
> > +bool domain_has_vuart(const struct domain *d)
> > +{
> > + return vuart_find_by_console_permission(d);
> > +}
> > +
> > +/*
> > + * Local variables:
> > + * mode: C
> > + * c-file-style: "BSD"
> > + * c-basic-offset: 4
> > + * indent-tabs-mode: nil
> > + * End:
> > + */
> > diff --git a/xen/common/keyhandler.c b/xen/common/keyhandler.c
> > index cb6df2823b00..156e64d9eb58 100644
> > --- a/xen/common/keyhandler.c
> > +++ b/xen/common/keyhandler.c
> > @@ -22,6 +22,7 @@
> > #include <xen/mm.h>
> > #include <xen/watchdog.h>
> > #include <xen/init.h>
> > +#include <xen/vuart.h>
> > #include <asm/div64.h>
> >
> > static unsigned char keypress_key;
> > @@ -352,6 +353,8 @@ static void cf_check dump_domains(unsigned char key)
> > v->periodic_period / 1000000);
> > }
> > }
> > +
> > + vuart_dump_state(d);
> > }
> >
> > for_each_domain ( d )
> > diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
> > index 9bd5b4825da6..d5164897a776 100644
> > --- a/xen/drivers/char/console.c
> > +++ b/xen/drivers/char/console.c
> > @@ -33,6 +33,7 @@
> > #include <asm/setup.h>
> > #include <xen/sections.h>
> > #include <xen/consoled.h>
> > +#include <xen/vuart.h>
> >
> > #ifdef CONFIG_X86
> > #include <asm/guest.h>
> > @@ -596,11 +597,12 @@ static void __serial_rx(char c)
> > if ( !d )
> > return;
> >
> > - if ( is_hardware_domain(d) )
> > + if ( is_hardware_domain(d) && !domain_has_vuart(d) )
> > {
> > /*
> > * Deliver input to the hardware domain buffer, unless it is
> > * already full.
> > + * NB: must be the first check: hardware domain may have emulated UART.
> > */
> > if ( (serial_rx_prod - serial_rx_cons) != SERIAL_RX_SIZE )
> > serial_rx_ring[SERIAL_RX_MASK(serial_rx_prod++)] = c;
> > @@ -611,6 +613,8 @@ static void __serial_rx(char c)
> > */
> > send_global_virq(VIRQ_CONSOLE);
> > }
> > + else if ( domain_has_vuart(d) )
> > + rc = vuart_put_rx(d, c);
> > #ifdef CONFIG_SBSA_VUART_CONSOLE
> > else
> > /* Deliver input to the emulated UART. */
> > diff --git a/xen/include/xen/serial.h b/xen/include/xen/serial.h
> > index 8e1844555208..d7e81f098359 100644
> > --- a/xen/include/xen/serial.h
> > +++ b/xen/include/xen/serial.h
> > @@ -36,6 +36,9 @@ struct vuart_info {
> > unsigned long data_off; /* Data register offset */
> > unsigned long status_off; /* Status register offset */
> > unsigned long status; /* Ready status value */
> > + unsigned int irq; /* Interrupt */
> > + const char *compatible; /* Compatible string */
> > + const char *name; /* User-friendly name */
> > };
> >
> > struct serial_port {
> > diff --git a/xen/include/xen/vuart.h b/xen/include/xen/vuart.h
> > new file mode 100644
> > index 000000000000..ca025b4179be
> > --- /dev/null
> > +++ b/xen/include/xen/vuart.h
> > @@ -0,0 +1,116 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * UART emulator framework.
> > + *
> > + * Copyright 2025 Ford Motor Company
> > + */
> > +
> > +#ifndef XEN_VUART_H
> > +#define XEN_VUART_H
> > +
> > +#include <xen/serial.h>
> > +#include <public/xen.h>
> > +
> > +struct vuart_emulator;
> > +
> > +enum {
> > + VUART_CONSOLE_INPUT = 0U << 1, /** Physical console input forwarding. */
>
> code style: single *
Ack
> This flag is zero, is that intended?
Will fix, thanks
>
>
> > +};
> > +
> > +
> > +/*
> > + * FIXME: #ifdef is temporary to avoid clash with
> > + * arch/arm/include/asm/domain.h
> > + */
> > +#ifdef CONFIG_VUART_FRAMEWORK
> > +struct vuart {
> > + const struct vuart_emulator *emulator;
> > + struct vuart_info *info;
> > + struct domain *owner;
> > + uint32_t flags;
> > + void *vdev;
> > +};
> > +#endif
> > +
> > +struct vuart_emulator {
> > + /* UART compatible string. Cannot be NULL or empty. */
> > + const char *compatible;
> > +
> > + /*
> > + * Allocate emulated UART state (RX/TX FIFOs, locks, initialize registers,
> > + * hook I/O handlers, etc.)
> > + * Cannot be NULL.
> > + */
> > + void *(*alloc)(struct domain *d, const struct vuart_info *info);
> > +
> > + /*
> > + * Release resources used to emulate UART state (flush RX/TX FIFOs, unhook
> > + * I/O handlers, etc.).
> > + * Cannot be NULL.
> > + */
> > + void (*free)(void *arg);
> > +
> > + /*
> > + * Print emulated UART state, including registers, on the console.
> > + * Can be NULL.
> > + */
> > + void (*dump_state)(void *arg);
> > +
> > + /*
> > + * Place character to the emulated RX FIFO.
> > + * Used to forward physical console input to the guest OS.
> > + * Can be NULL.
> > + */
> > + int (*put_rx)(void *arg, char c);
> > +};
> > +
> > +#define VUART_REGISTER(name, x) \
> > + static const struct vuart_emulator name##_entry \
> > + __used_section(".data.rel.ro.vuart") = x
> > +
> > +struct vuart *vuart_find_by_io_range(struct domain *d,
> > + unsigned long base_addr,
> > + unsigned long size);
> > +
> > +int vuart_put_rx(struct domain *d, char c);
> > +
> > +#ifdef CONFIG_VUART_FRAMEWORK
> > +
> > +int vuart_init(struct domain *d, struct vuart_info *info);
> > +void vuart_deinit(struct domain *d);
> > +void vuart_dump_state(const struct domain *d);
> > +bool domain_has_vuart(const struct domain *d);
> > +
> > +#else
> > +
> > +static inline int vuart_init(struct domain *d, struct vuart_info *info)
> > +{
> > + return 0;
> > +}
> > +
> > +static inline void vuart_deinit(struct domain *d)
> > +{
> > +}
> > +
> > +static inline void vuart_dump_state(const struct domain *d)
> > +{
> > +}
> > +
> > +static inline bool domain_has_vuart(const struct domain *d)
> > +{
> > + return false;
> > +}
> > +
> > +#endif /* CONFIG_VUART_FRAMEWORK */
> > +
> > +#endif /* XEN_VUART_H */
> > +
> > +/*
> > + * Local variables:
> > + * mode: C
> > + * c-file-style: "BSD"
> > + * c-basic-offset: 4
> > + * indent-tabs-mode: nil
> > + * End:
> > + */
> > +
> > diff --git a/xen/include/xen/xen.lds.h b/xen/include/xen/xen.lds.h
> > index b126dfe88792..2d65f32ddad3 100644
> > --- a/xen/include/xen/xen.lds.h
> > +++ b/xen/include/xen/xen.lds.h
> > @@ -194,4 +194,14 @@
> > #define VPCI_ARRAY
> > #endif
> >
> > +#ifdef CONFIG_VUART_FRAMEWORK
> > +#define VUART_ARRAY \
> > + . = ALIGN(POINTER_ALIGN); \
> > + vuart_array_start = .; \
> > + *(.data.rel.ro.vuart) \
> > + vuart_array_end = .;
> > +#else
> > +#define VUART_ARRAY
> > +#endif
> > +
> > #endif /* __XEN_LDS_H__ */
> > --
> > 2.51.0
> >
On 29.08.2025 21:27, Stefano Stabellini wrote:
> On Thu, 28 Aug 2025, dmukhin@xen.org wrote:
>> --- /dev/null
>> +++ b/xen/common/emul/vuart/vuart.c
>> @@ -0,0 +1,156 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * UART emulator framework.
>> + *
>> + * Copyright 2025 Ford Motor Company
>> + */
>> +
>> +#include <xen/err.h>
>> +#include <xen/sched.h>
>> +#include <xen/vuart.h>
>> +#include <xen/xvmalloc.h>
>> +
>> +#define for_each_emulator(e) \
>> + for ( e = vuart_array_start; e < vuart_array_end; e++ )
>> +
>> +extern const struct vuart_emulator vuart_array_start[];
>> +extern const struct vuart_emulator vuart_array_end[];
>> +
>> +static const struct vuart_emulator *
>> +vuart_match_by_compatible(struct domain *d, const char *compat)
>> +{
>> + const struct vuart_emulator *emulator;
>> +
>> + if ( d->console.vuart )
>> + return NULL;
>> +
>> + for_each_emulator(emulator)
>> + if ( emulator->compatible &&
>> + !strncmp(emulator->compatible, compat,
>> + strlen(emulator->compatible)) )
>
> strncmp will continue until the given count even if compat is shorter
Not really, one string having a nul char and the other not having one is a
difference, at which point comparison will stop. There would be a problem
if "compat" didn't point to a nul-terminated string, though (and I didn't
check that aspect, not the least because then "shorter" doesn't really
make much sense without a length passed in).
Jan
On Mon, Sep 01, 2025 at 10:14:04AM +0200, Jan Beulich wrote:
> On 29.08.2025 21:27, Stefano Stabellini wrote:
> > On Thu, 28 Aug 2025, dmukhin@xen.org wrote:
> >> --- /dev/null
> >> +++ b/xen/common/emul/vuart/vuart.c
> >> @@ -0,0 +1,156 @@
> >> +/* SPDX-License-Identifier: GPL-2.0-only */
> >> +/*
> >> + * UART emulator framework.
> >> + *
> >> + * Copyright 2025 Ford Motor Company
> >> + */
> >> +
> >> +#include <xen/err.h>
> >> +#include <xen/sched.h>
> >> +#include <xen/vuart.h>
> >> +#include <xen/xvmalloc.h>
> >> +
> >> +#define for_each_emulator(e) \
> >> + for ( e = vuart_array_start; e < vuart_array_end; e++ )
> >> +
> >> +extern const struct vuart_emulator vuart_array_start[];
> >> +extern const struct vuart_emulator vuart_array_end[];
> >> +
> >> +static const struct vuart_emulator *
> >> +vuart_match_by_compatible(struct domain *d, const char *compat)
> >> +{
> >> + const struct vuart_emulator *emulator;
> >> +
> >> + if ( d->console.vuart )
> >> + return NULL;
> >> +
> >> + for_each_emulator(emulator)
> >> + if ( emulator->compatible &&
> >> + !strncmp(emulator->compatible, compat,
> >> + strlen(emulator->compatible)) )
> >
> > strncmp will continue until the given count even if compat is shorter
>
> Not really, one string having a nul char and the other not having one is a
> difference, at which point comparison will stop. There would be a problem
> if "compat" didn't point to a nul-terminated string, though (and I didn't
> check that aspect, not the least because then "shorter" doesn't really
> make much sense without a length passed in).
re: NUL-termination: current assumption is that both compat and
emulator->compatible are NUL-terminated.
Current `compat` comes from the hardcoded NUL-terminated string (vuart_info).
In case of `compat` is not NUL-terminated (I plan to populate the field from
xl in the future), strncmp() will stop after strlen(emulator->compatible)
bytes.
On 02.09.2025 00:27, dmukhin@xen.org wrote:
> On Mon, Sep 01, 2025 at 10:14:04AM +0200, Jan Beulich wrote:
>> On 29.08.2025 21:27, Stefano Stabellini wrote:
>>> On Thu, 28 Aug 2025, dmukhin@xen.org wrote:
>>>> --- /dev/null
>>>> +++ b/xen/common/emul/vuart/vuart.c
>>>> @@ -0,0 +1,156 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0-only */
>>>> +/*
>>>> + * UART emulator framework.
>>>> + *
>>>> + * Copyright 2025 Ford Motor Company
>>>> + */
>>>> +
>>>> +#include <xen/err.h>
>>>> +#include <xen/sched.h>
>>>> +#include <xen/vuart.h>
>>>> +#include <xen/xvmalloc.h>
>>>> +
>>>> +#define for_each_emulator(e) \
>>>> + for ( e = vuart_array_start; e < vuart_array_end; e++ )
>>>> +
>>>> +extern const struct vuart_emulator vuart_array_start[];
>>>> +extern const struct vuart_emulator vuart_array_end[];
>>>> +
>>>> +static const struct vuart_emulator *
>>>> +vuart_match_by_compatible(struct domain *d, const char *compat)
>>>> +{
>>>> + const struct vuart_emulator *emulator;
>>>> +
>>>> + if ( d->console.vuart )
>>>> + return NULL;
>>>> +
>>>> + for_each_emulator(emulator)
>>>> + if ( emulator->compatible &&
>>>> + !strncmp(emulator->compatible, compat,
>>>> + strlen(emulator->compatible)) )
>>>
>>> strncmp will continue until the given count even if compat is shorter
>>
>> Not really, one string having a nul char and the other not having one is a
>> difference, at which point comparison will stop. There would be a problem
>> if "compat" didn't point to a nul-terminated string, though (and I didn't
>> check that aspect, not the least because then "shorter" doesn't really
>> make much sense without a length passed in).
>
> re: NUL-termination: current assumption is that both compat and
> emulator->compatible are NUL-terminated.
>
> Current `compat` comes from the hardcoded NUL-terminated string (vuart_info).
>
> In case of `compat` is not NUL-terminated (I plan to populate the field from
> xl in the future), strncmp() will stop after strlen(emulator->compatible)
> bytes.
Which might be too late; if not nul-terminated, "compat" may extend past a
page boundary, with the latter page not mapped.
Jan
© 2016 - 2025 Red Hat, Inc.