From: Liran Alon <liran.alon@oracle.com>
vmport_ioport_read() returns the value that should propagate to vCPU EAX
register when guest reads VMPort IOPort (i.e. By x86 IN instruction).
However, because vmport_ioport_read() calls cpu_synchronize_state(), the
returned value gets overridden by the value in QEMU vCPU EAX register.
i.e. cpu->env.regs[R_EAX].
To fix this issue, change vmport_ioport_read() to explicitly override
cpu->env.regs[R_EAX] with the value it wish to propagate to vCPU EAX
register.
Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Message-Id: <20200312165431.82118-4-liran.alon@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
hw/core/machine.c | 1 +
hw/i386/vmport.c | 32 +++++++++++++++++++++++++++++---
2 files changed, 30 insertions(+), 3 deletions(-)
diff --git a/hw/core/machine.c b/hw/core/machine.c
index bb3a7b18b1..83f0fe5c91 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -43,6 +43,7 @@ GlobalProperty hw_compat_4_2[] = {
{ "qxl", "revision", "4" },
{ "qxl-vga", "revision", "4" },
{ "fw_cfg", "acpi-mr-restore", "false" },
+ { "vmport", "x-read-set-eax", "off" },
};
const size_t hw_compat_4_2_len = G_N_ELEMENTS(hw_compat_4_2);
diff --git a/hw/i386/vmport.c b/hw/i386/vmport.c
index 5985167dcf..3bb420a245 100644
--- a/hw/i386/vmport.c
+++ b/hw/i386/vmport.c
@@ -43,6 +43,11 @@
#define VMPORT_ENTRIES 0x2c
#define VMPORT_MAGIC 0x564D5868
+/* Compatibility flags for migration */
+#define VMPORT_COMPAT_READ_SET_EAX_BIT 0
+#define VMPORT_COMPAT_READ_SET_EAX \
+ (1 << VMPORT_COMPAT_READ_SET_EAX_BIT)
+
#define VMPORT(obj) OBJECT_CHECK(VMPortState, (obj), TYPE_VMPORT)
typedef struct VMPortState {
@@ -51,6 +56,8 @@ typedef struct VMPortState {
MemoryRegion io;
VMPortReadFunc *func[VMPORT_ENTRIES];
void *opaque[VMPORT_ENTRIES];
+
+ uint32_t compat_flags;
} VMPortState;
static VMPortState *port_state;
@@ -80,17 +87,33 @@ static uint64_t vmport_ioport_read(void *opaque, hwaddr addr,
eax = env->regs[R_EAX];
if (eax != VMPORT_MAGIC) {
- return eax;
+ goto out;
}
command = env->regs[R_ECX];
trace_vmport_command(command);
if (command >= VMPORT_ENTRIES || !s->func[command]) {
qemu_log_mask(LOG_UNIMP, "vmport: unknown command %x\n", command);
- return eax;
+ goto out;
+ }
+
+ eax = s->func[command](s->opaque[command], addr);
+
+out:
+ /*
+ * The call above to cpu_synchronize_state() gets vCPU registers values
+ * to QEMU but also cause QEMU to write QEMU vCPU registers values to
+ * vCPU implementation (e.g. Accelerator such as KVM) just before
+ * resuming guest.
+ *
+ * Therefore, in order to make IOPort return value propagate to
+ * guest EAX, we need to explicitly update QEMU EAX register value.
+ */
+ if (s->compat_flags & VMPORT_COMPAT_READ_SET_EAX) {
+ cpu->env.regs[R_EAX] = eax;
}
- return s->func[command](s->opaque[command], addr);
+ return eax;
}
static void vmport_ioport_write(void *opaque, hwaddr addr,
@@ -142,6 +165,9 @@ static void vmport_realizefn(DeviceState *dev, Error **errp)
}
static Property vmport_properties[] = {
+ /* Used to enforce compatibility for migration */
+ DEFINE_PROP_BIT("x-read-set-eax", VMPortState, compat_flags,
+ VMPORT_COMPAT_READ_SET_EAX_BIT, true),
DEFINE_PROP_END_OF_LIST(),
};
--
2.26.2