From: Bobby Eshleman <bobbyeshleman@gmail.com>
Additionally, this patch introduces macros in fence.h,
which are utilized in atomic.h.
atomic##prefix##_*xchg_*(atomic##prefix##_t *v, c_t n)
were updated to use __*xchg_generic().
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
---
Changes in V4:
- do changes related to the updates of [PATCH v3 13/34] xen/riscv: introduce cmpxchg.h
- drop casts in read_atomic_size(), write_atomic(), add_sized()
- tabs -> spaces
- drop #ifdef CONFIG_SMP ... #endif in fence.ha as it is simpler to handle NR_CPUS=1
the same as NR_CPUS>1 with accepting less than ideal performance.
---
Changes in V3:
- update the commit message
- add SPDX for fence.h
- code style fixes
- Remove /* TODO: ... */ for add_sized macros. It looks correct to me.
- re-order the patch
- merge to this patch fence.h
---
Changes in V2:
- Change an author of commit. I got this header from Bobby's old repo.
---
xen/arch/riscv/include/asm/atomic.h | 395 ++++++++++++++++++++++++++++
xen/arch/riscv/include/asm/fence.h | 8 +
2 files changed, 403 insertions(+)
create mode 100644 xen/arch/riscv/include/asm/atomic.h
create mode 100644 xen/arch/riscv/include/asm/fence.h
diff --git a/xen/arch/riscv/include/asm/atomic.h b/xen/arch/riscv/include/asm/atomic.h
new file mode 100644
index 0000000000..267d3c0803
--- /dev/null
+++ b/xen/arch/riscv/include/asm/atomic.h
@@ -0,0 +1,395 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Taken and modified from Linux.
+ *
+ * atomic##prefix##_*xchg_*(atomic##prefix##_t *v, c_t n) were updated to use
+ * __*xchg_generic()
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Copyright (C) 2012 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ * Copyright (C) 2021 Vates SAS
+ */
+
+#ifndef _ASM_RISCV_ATOMIC_H
+#define _ASM_RISCV_ATOMIC_H
+
+#include <xen/atomic.h>
+#include <asm/cmpxchg.h>
+#include <asm/fence.h>
+#include <asm/io.h>
+#include <asm/system.h>
+
+void __bad_atomic_size(void);
+
+static always_inline void read_atomic_size(const volatile void *p,
+ void *res,
+ unsigned int size)
+{
+ switch ( size )
+ {
+ case 1: *(uint8_t *)res = readb(p); break;
+ case 2: *(uint16_t *)res = readw(p); break;
+ case 4: *(uint32_t *)res = readl(p); break;
+ case 8: *(uint32_t *)res = readq(p); break;
+ default: __bad_atomic_size(); break;
+ }
+}
+
+#define read_atomic(p) ({ \
+ union { typeof(*p) val; char c[0]; } x_; \
+ read_atomic_size(p, x_.c, sizeof(*p)); \
+ x_.val; \
+})
+
+#define write_atomic(p, x) \
+({ \
+ typeof(*p) x__ = (x); \
+ switch ( sizeof(*p) ) \
+ { \
+ case 1: writeb((uint8_t)x__, p); break; \
+ case 2: writew((uint16_t)x__, p); break; \
+ case 4: writel((uint32_t)x__, p); break; \
+ case 8: writeq((uint64_t)x__, p); break; \
+ default: __bad_atomic_size(); break; \
+ } \
+ x__; \
+})
+
+#define add_sized(p, x) \
+({ \
+ typeof(*(p)) x__ = (x); \
+ switch ( sizeof(*(p)) ) \
+ { \
+ case 1: writeb(read_atomic(p) + x__, p); break; \
+ case 2: writew(read_atomic(p) + x__, p); break; \
+ case 4: writel(read_atomic(p) + x__, p); break; \
+ default: __bad_atomic_size(); break; \
+ } \
+})
+
+/*
+ * __unqual_scalar_typeof(x) - Declare an unqualified scalar type, leaving
+ * non-scalar types unchanged.
+ *
+ * Prefer C11 _Generic for better compile-times and simpler code. Note: 'char'
+ * is not type-compatible with 'signed char', and we define a separate case.
+ */
+#define __scalar_type_to_expr_cases(type) \
+ unsigned type: (unsigned type)0, \
+ signed type: (signed type)0
+
+#define __unqual_scalar_typeof(x) typeof( \
+ _Generic((x), \
+ char: (char)0, \
+ __scalar_type_to_expr_cases(char), \
+ __scalar_type_to_expr_cases(short), \
+ __scalar_type_to_expr_cases(int), \
+ __scalar_type_to_expr_cases(long), \
+ __scalar_type_to_expr_cases(long long), \
+ default: (x)))
+
+#define READ_ONCE(x) (*(const volatile __unqual_scalar_typeof(x) *)&(x))
+#define WRITE_ONCE(x, val) \
+ do { \
+ *(volatile typeof(x) *)&(x) = (val); \
+ } while (0)
+
+#define __atomic_acquire_fence() \
+ __asm__ __volatile__( RISCV_ACQUIRE_BARRIER "" ::: "memory" )
+
+#define __atomic_release_fence() \
+ __asm__ __volatile__( RISCV_RELEASE_BARRIER "" ::: "memory" );
+
+static inline int atomic_read(const atomic_t *v)
+{
+ return READ_ONCE(v->counter);
+}
+
+static inline int _atomic_read(atomic_t v)
+{
+ return v.counter;
+}
+
+static inline void atomic_set(atomic_t *v, int i)
+{
+ WRITE_ONCE(v->counter, i);
+}
+
+static inline void _atomic_set(atomic_t *v, int i)
+{
+ v->counter = i;
+}
+
+static inline int atomic_sub_and_test(int i, atomic_t *v)
+{
+ return atomic_sub_return(i, v) == 0;
+}
+
+static inline void atomic_inc(atomic_t *v)
+{
+ atomic_add(1, v);
+}
+
+static inline int atomic_inc_return(atomic_t *v)
+{
+ return atomic_add_return(1, v);
+}
+
+static inline void atomic_dec(atomic_t *v)
+{
+ atomic_sub(1, v);
+}
+
+static inline int atomic_dec_return(atomic_t *v)
+{
+ return atomic_sub_return(1, v);
+}
+
+static inline int atomic_dec_and_test(atomic_t *v)
+{
+ return atomic_sub_return(1, v) == 0;
+}
+
+static inline int atomic_add_negative(int i, atomic_t *v)
+{
+ return atomic_add_return(i, v) < 0;
+}
+
+static inline int atomic_inc_and_test(atomic_t *v)
+{
+ return atomic_add_return(1, v) == 0;
+}
+
+/*
+ * First, the atomic ops that have no ordering constraints and therefor don't
+ * have the AQ or RL bits set. These don't return anything, so there's only
+ * one version to worry about.
+ */
+#define ATOMIC_OP(op, asm_op, I, asm_type, c_type, prefix) \
+static inline \
+void atomic##prefix##_##op(c_type i, atomic##prefix##_t *v) \
+{ \
+ __asm__ __volatile__ ( \
+ " amo" #asm_op "." #asm_type " zero, %1, %0" \
+ : "+A" (v->counter) \
+ : "r" (I) \
+ : "memory" ); \
+} \
+
+#define ATOMIC_OPS(op, asm_op, I) \
+ ATOMIC_OP (op, asm_op, I, w, int, )
+
+ATOMIC_OPS(add, add, i)
+ATOMIC_OPS(sub, add, -i)
+ATOMIC_OPS(and, and, i)
+ATOMIC_OPS( or, or, i)
+ATOMIC_OPS(xor, xor, i)
+
+#undef ATOMIC_OP
+#undef ATOMIC_OPS
+
+/*
+ * Atomic ops that have ordered, relaxed, acquire, and release variants.
+ * There's two flavors of these: the arithmatic ops have both fetch and return
+ * versions, while the logical ops only have fetch versions.
+ */
+#define ATOMIC_FETCH_OP(op, asm_op, I, asm_type, c_type, prefix) \
+static inline \
+c_type atomic##prefix##_fetch_##op##_relaxed(c_type i, \
+ atomic##prefix##_t *v) \
+{ \
+ register c_type ret; \
+ __asm__ __volatile__ ( \
+ " amo" #asm_op "." #asm_type " %1, %2, %0" \
+ : "+A" (v->counter), "=r" (ret) \
+ : "r" (I) \
+ : "memory" ); \
+ return ret; \
+} \
+static inline \
+c_type atomic##prefix##_fetch_##op(c_type i, atomic##prefix##_t *v) \
+{ \
+ register c_type ret; \
+ __asm__ __volatile__ ( \
+ " amo" #asm_op "." #asm_type ".aqrl %1, %2, %0" \
+ : "+A" (v->counter), "=r" (ret) \
+ : "r" (I) \
+ : "memory" ); \
+ return ret; \
+}
+
+#define ATOMIC_OP_RETURN(op, asm_op, c_op, I, asm_type, c_type, prefix) \
+static inline \
+c_type atomic##prefix##_##op##_return_relaxed(c_type i, \
+ atomic##prefix##_t *v) \
+{ \
+ return atomic##prefix##_fetch_##op##_relaxed(i, v) c_op I; \
+} \
+static inline \
+c_type atomic##prefix##_##op##_return(c_type i, atomic##prefix##_t *v) \
+{ \
+ return atomic##prefix##_fetch_##op(i, v) c_op I; \
+}
+
+#define ATOMIC_OPS(op, asm_op, c_op, I) \
+ ATOMIC_FETCH_OP( op, asm_op, I, w, int, ) \
+ ATOMIC_OP_RETURN(op, asm_op, c_op, I, w, int, )
+
+ATOMIC_OPS(add, add, +, i)
+ATOMIC_OPS(sub, add, +, -i)
+
+#define atomic_add_return_relaxed atomic_add_return_relaxed
+#define atomic_sub_return_relaxed atomic_sub_return_relaxed
+#define atomic_add_return atomic_add_return
+#define atomic_sub_return atomic_sub_return
+
+#define atomic_fetch_add_relaxed atomic_fetch_add_relaxed
+#define atomic_fetch_sub_relaxed atomic_fetch_sub_relaxed
+#define atomic_fetch_add atomic_fetch_add
+#define atomic_fetch_sub atomic_fetch_sub
+
+#undef ATOMIC_OPS
+
+#define ATOMIC_OPS(op, asm_op, I) \
+ ATOMIC_FETCH_OP(op, asm_op, I, w, int, )
+
+ATOMIC_OPS(and, and, i)
+ATOMIC_OPS( or, or, i)
+ATOMIC_OPS(xor, xor, i)
+
+#define atomic_fetch_and_relaxed atomic_fetch_and_relaxed
+#define atomic_fetch_or_relaxed atomic_fetch_or_relaxed
+#define atomic_fetch_xor_relaxed atomic_fetch_xor_relaxed
+#define atomic_fetch_and atomic_fetch_and
+#define atomic_fetch_or atomic_fetch_or
+#define atomic_fetch_xor atomic_fetch_xor
+
+#undef ATOMIC_OPS
+
+#undef ATOMIC_FETCH_OP
+#undef ATOMIC_OP_RETURN
+
+/* This is required to provide a full barrier on success. */
+static inline int atomic_add_unless(atomic_t *v, int a, int u)
+{
+ int prev, rc;
+
+ __asm__ __volatile__ (
+ "0: lr.w %[p], %[c]\n"
+ " beq %[p], %[u], 1f\n"
+ " add %[rc], %[p], %[a]\n"
+ " sc.w.rl %[rc], %[rc], %[c]\n"
+ " bnez %[rc], 0b\n"
+ " fence rw, rw\n"
+ "1:\n"
+ : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
+ : [a]"r" (a), [u]"r" (u)
+ : "memory");
+ return prev;
+}
+#define atomic_fetch_add_unless atomic_fetch_add_unless
+
+/*
+ * atomic_{cmp,}xchg is required to have exactly the same ordering semantics as
+ * {cmp,}xchg and the operations that return, so they need a full barrier.
+ */
+#define ATOMIC_OP(c_t, prefix, size) \
+static inline \
+c_t atomic##prefix##_xchg_relaxed(atomic##prefix##_t *v, c_t n) \
+{ \
+ return __xchg_generic(&(v->counter), n, size, "", "", ""); \
+} \
+static inline \
+c_t atomic##prefix##_xchg_acquire(atomic##prefix##_t *v, c_t n) \
+{ \
+ return __xchg_generic(&(v->counter), n, size, \
+ "", "", RISCV_ACQUIRE_BARRIER); \
+} \
+static inline \
+c_t atomic##prefix##_xchg_release(atomic##prefix##_t *v, c_t n) \
+{ \
+ return __xchg_generic(&(v->counter), n, size, \
+ "", RISCV_RELEASE_BARRIER, ""); \
+} \
+static inline \
+c_t atomic##prefix##_xchg(atomic##prefix##_t *v, c_t n) \
+{ \
+ return __xchg_generic(&(v->counter), n, size, \
+ ".aqrl", "", ""); \
+} \
+static inline \
+c_t atomic##prefix##_cmpxchg_relaxed(atomic##prefix##_t *v, \
+ c_t o, c_t n) \
+{ \
+ return __cmpxchg_generic(&(v->counter), o, n, size, \
+ "", "", ""); \
+} \
+static inline \
+c_t atomic##prefix##_cmpxchg_acquire(atomic##prefix##_t *v, \
+ c_t o, c_t n) \
+{ \
+ return __cmpxchg_generic(&(v->counter), o, n, size, \
+ "", "", RISCV_ACQUIRE_BARRIER); \
+} \
+static inline \
+c_t atomic##prefix##_cmpxchg_release(atomic##prefix##_t *v, \
+ c_t o, c_t n) \
+{ \
+ return __cmpxchg_generic(&(v->counter), o, n, size, \
+ "", RISCV_RELEASE_BARRIER, ""); \
+} \
+static inline \
+c_t atomic##prefix##_cmpxchg(atomic##prefix##_t *v, c_t o, c_t n) \
+{ \
+ return __cmpxchg_generic(&(v->counter), o, n, size, \
+ ".rl", "", " fence rw, rw\n"); \
+}
+
+#define ATOMIC_OPS() \
+ ATOMIC_OP(int, , 4)
+
+ATOMIC_OPS()
+
+#define atomic_xchg_relaxed atomic_xchg_relaxed
+#define atomic_xchg_acquire atomic_xchg_acquire
+#define atomic_xchg_release atomic_xchg_release
+#define atomic_xchg atomic_xchg
+#define atomic_cmpxchg_relaxed atomic_cmpxchg_relaxed
+#define atomic_cmpxchg_acquire atomic_cmpxchg_acquire
+#define atomic_cmpxchg_release atomic_cmpxchg_release
+#define atomic_cmpxchg atomic_cmpxchg
+
+#undef ATOMIC_OPS
+#undef ATOMIC_OP
+
+static inline int atomic_sub_if_positive(atomic_t *v, int offset)
+{
+ int prev, rc;
+
+ __asm__ __volatile__ (
+ "0: lr.w %[p], %[c]\n"
+ " sub %[rc], %[p], %[o]\n"
+ " bltz %[rc], 1f\n"
+ " sc.w.rl %[rc], %[rc], %[c]\n"
+ " bnez %[rc], 0b\n"
+ " fence rw, rw\n"
+ "1:\n"
+ : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
+ : [o]"r" (offset)
+ : "memory" );
+ return prev - offset;
+}
+
+#define atomic_dec_if_positive(v) atomic_sub_if_positive(v, 1)
+
+#endif /* _ASM_RISCV_ATOMIC_H */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/arch/riscv/include/asm/fence.h b/xen/arch/riscv/include/asm/fence.h
new file mode 100644
index 0000000000..ff3f23dbd7
--- /dev/null
+++ b/xen/arch/riscv/include/asm/fence.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _ASM_RISCV_FENCE_H
+#define _ASM_RISCV_FENCE_H
+
+#define RISCV_ACQUIRE_BARRIER "\tfence r , rw\n"
+#define RISCV_RELEASE_BARRIER "\tfence rw, w\n"
+
+#endif /* _ASM_RISCV_FENCE_H */
--
2.43.0Hi,
On 05/02/2024 15:32, Oleksii Kurochko wrote:
> From: Bobby Eshleman <bobbyeshleman@gmail.com>
>
> Additionally, this patch introduces macros in fence.h,
> which are utilized in atomic.h.
>
> atomic##prefix##_*xchg_*(atomic##prefix##_t *v, c_t n)
> were updated to use __*xchg_generic().
>
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
The author is Bobby, but I don't see a Signed-off-by. Did you forgot it?
> ---
> Changes in V4:
> - do changes related to the updates of [PATCH v3 13/34] xen/riscv: introduce cmpxchg.h
> - drop casts in read_atomic_size(), write_atomic(), add_sized()
> - tabs -> spaces
> - drop #ifdef CONFIG_SMP ... #endif in fence.ha as it is simpler to handle NR_CPUS=1
> the same as NR_CPUS>1 with accepting less than ideal performance.
> ---
> Changes in V3:
> - update the commit message
> - add SPDX for fence.h
> - code style fixes
> - Remove /* TODO: ... */ for add_sized macros. It looks correct to me.
> - re-order the patch
> - merge to this patch fence.h
> ---
> Changes in V2:
> - Change an author of commit. I got this header from Bobby's old repo.
> ---
> xen/arch/riscv/include/asm/atomic.h | 395 ++++++++++++++++++++++++++++
> xen/arch/riscv/include/asm/fence.h | 8 +
> 2 files changed, 403 insertions(+)
> create mode 100644 xen/arch/riscv/include/asm/atomic.h
> create mode 100644 xen/arch/riscv/include/asm/fence.h
>
> diff --git a/xen/arch/riscv/include/asm/atomic.h b/xen/arch/riscv/include/asm/atomic.h
> new file mode 100644
> index 0000000000..267d3c0803
> --- /dev/null
> +++ b/xen/arch/riscv/include/asm/atomic.h
> @@ -0,0 +1,395 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Taken and modified from Linux.
Which version of Linux? Can you also spell out what are the big changes?
This would be helpful if we need to re-sync.
> + *
> + * atomic##prefix##_*xchg_*(atomic##prefix##_t *v, c_t n) were updated to use
> + * __*xchg_generic()
> + *
> + * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
> + * Copyright (C) 2012 Regents of the University of California
> + * Copyright (C) 2017 SiFive
> + * Copyright (C) 2021 Vates SAS
> + */
> +
> +#ifndef _ASM_RISCV_ATOMIC_H
> +#define _ASM_RISCV_ATOMIC_H
> +
> +#include <xen/atomic.h>
> +#include <asm/cmpxchg.h>
> +#include <asm/fence.h>
> +#include <asm/io.h>
> +#include <asm/system.h>
> +
> +void __bad_atomic_size(void);
> +
> +static always_inline void read_atomic_size(const volatile void *p,
> + void *res,
> + unsigned int size)
> +{
> + switch ( size )
> + {
> + case 1: *(uint8_t *)res = readb(p); break;
> + case 2: *(uint16_t *)res = readw(p); break;
> + case 4: *(uint32_t *)res = readl(p); break;
> + case 8: *(uint32_t *)res = readq(p); break;
> + default: __bad_atomic_size(); break;
> + }
> +}
> +
> +#define read_atomic(p) ({ \
> + union { typeof(*p) val; char c[0]; } x_; \
> + read_atomic_size(p, x_.c, sizeof(*p)); \
> + x_.val; \
> +})
> +
> +#define write_atomic(p, x) \
> +({ \
> + typeof(*p) x__ = (x); \
> + switch ( sizeof(*p) ) \
> + { \
> + case 1: writeb((uint8_t)x__, p); break; \
> + case 2: writew((uint16_t)x__, p); break; \
> + case 4: writel((uint32_t)x__, p); break; \
> + case 8: writeq((uint64_t)x__, p); break; \
> + default: __bad_atomic_size(); break; \
> + } \
> + x__; \
> +})
> +
> +#define add_sized(p, x) \
> +({ \
> + typeof(*(p)) x__ = (x); \
> + switch ( sizeof(*(p)) ) \
> + { \
> + case 1: writeb(read_atomic(p) + x__, p); break; \
> + case 2: writew(read_atomic(p) + x__, p); break; \
> + case 4: writel(read_atomic(p) + x__, p); break; \
> + default: __bad_atomic_size(); break; \
> + } \
> +})
> +
> +/*
> + * __unqual_scalar_typeof(x) - Declare an unqualified scalar type, leaving
> + * non-scalar types unchanged.
> + *
> + * Prefer C11 _Generic for better compile-times and simpler code. Note: 'char'
Xen is technically built using c99/gnu99. So it is feels a bit odd to
introduce a C11 feature. I see that _Generic is already used in PPC...
However, if we decide to add more use of it, then I think this should at
minimum be documented in docs/misra/C-language-toolchain.rst (the more
if we plan the macro is moved to common as Jan suggested).
Cheers,
--
Julien Grall
Hi Julien,
On Sun, 2024-02-18 at 19:22 +0000, Julien Grall wrote:
> Hi,
>
> On 05/02/2024 15:32, Oleksii Kurochko wrote:
> > From: Bobby Eshleman <bobbyeshleman@gmail.com>
> >
> > Additionally, this patch introduces macros in fence.h,
> > which are utilized in atomic.h.
> >
> > atomic##prefix##_*xchg_*(atomic##prefix##_t *v, c_t n)
> > were updated to use __*xchg_generic().
> >
> > Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
>
> The author is Bobby, but I don't see a Signed-off-by. Did you forgot
> it?
I missed to add that as I thought that it would be enough to change a
commit author.
>
> > ---
> > Changes in V4:
> > - do changes related to the updates of [PATCH v3 13/34]
> > xen/riscv: introduce cmpxchg.h
> > - drop casts in read_atomic_size(), write_atomic(), add_sized()
> > - tabs -> spaces
> > - drop #ifdef CONFIG_SMP ... #endif in fence.ha as it is simpler
> > to handle NR_CPUS=1
> > the same as NR_CPUS>1 with accepting less than ideal
> > performance.
> > ---
> > Changes in V3:
> > - update the commit message
> > - add SPDX for fence.h
> > - code style fixes
> > - Remove /* TODO: ... */ for add_sized macros. It looks correct
> > to me.
> > - re-order the patch
> > - merge to this patch fence.h
> > ---
> > Changes in V2:
> > - Change an author of commit. I got this header from Bobby's old
> > repo.
> > ---
> > xen/arch/riscv/include/asm/atomic.h | 395
> > ++++++++++++++++++++++++++++
> > xen/arch/riscv/include/asm/fence.h | 8 +
> > 2 files changed, 403 insertions(+)
> > create mode 100644 xen/arch/riscv/include/asm/atomic.h
> > create mode 100644 xen/arch/riscv/include/asm/fence.h
> >
> > diff --git a/xen/arch/riscv/include/asm/atomic.h
> > b/xen/arch/riscv/include/asm/atomic.h
> > new file mode 100644
> > index 0000000000..267d3c0803
> > --- /dev/null
> > +++ b/xen/arch/riscv/include/asm/atomic.h
> > @@ -0,0 +1,395 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Taken and modified from Linux.
>
> Which version of Linux? Can you also spell out what are the big
> changes?
> This would be helpful if we need to re-sync.
Sure, I'll add the changes here.
>
> > + *
> > + * atomic##prefix##_*xchg_*(atomic##prefix##_t *v, c_t n) were
> > updated to use
> > + * __*xchg_generic()
> > + *
> > + * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
> > + * Copyright (C) 2012 Regents of the University of California
> > + * Copyright (C) 2017 SiFive
> > + * Copyright (C) 2021 Vates SAS
> > + */
> > +
> > +#ifndef _ASM_RISCV_ATOMIC_H
> > +#define _ASM_RISCV_ATOMIC_H
> > +
> > +#include <xen/atomic.h>
> > +#include <asm/cmpxchg.h>
> > +#include <asm/fence.h>
> > +#include <asm/io.h>
> > +#include <asm/system.h>
> > +
> > +void __bad_atomic_size(void);
> > +
> > +static always_inline void read_atomic_size(const volatile void *p,
> > + void *res,
> > + unsigned int size)
> > +{
> > + switch ( size )
> > + {
> > + case 1: *(uint8_t *)res = readb(p); break;
> > + case 2: *(uint16_t *)res = readw(p); break;
> > + case 4: *(uint32_t *)res = readl(p); break;
> > + case 8: *(uint32_t *)res = readq(p); break;
> > + default: __bad_atomic_size(); break;
> > + }
> > +}
> > +
> > +#define read_atomic(p) ({ \
> > + union { typeof(*p) val; char c[0]; } x_; \
> > + read_atomic_size(p, x_.c, sizeof(*p)); \
> > + x_.val; \
> > +})
> > +
> > +#define write_atomic(p, x) \
> > +({ \
> > + typeof(*p) x__ = (x); \
> > + switch ( sizeof(*p) ) \
> > + { \
> > + case 1: writeb((uint8_t)x__, p); break; \
> > + case 2: writew((uint16_t)x__, p); break; \
> > + case 4: writel((uint32_t)x__, p); break; \
> > + case 8: writeq((uint64_t)x__, p); break; \
> > + default: __bad_atomic_size(); break; \
> > + } \
> > + x__; \
> > +})
> > +
> > +#define add_sized(p, x) \
> > +({ \
> > + typeof(*(p)) x__ = (x); \
> > + switch ( sizeof(*(p)) ) \
> > + { \
> > + case 1: writeb(read_atomic(p) + x__, p); break; \
> > + case 2: writew(read_atomic(p) + x__, p); break; \
> > + case 4: writel(read_atomic(p) + x__, p); break; \
> > + default: __bad_atomic_size(); break; \
> > + } \
> > +})
> > +
> > +/*
> > + * __unqual_scalar_typeof(x) - Declare an unqualified scalar
> > type, leaving
> > + * non-scalar types unchanged.
> > + *
> > + * Prefer C11 _Generic for better compile-times and simpler code.
> > Note: 'char'
>
> Xen is technically built using c99/gnu99. So it is feels a bit odd to
> introduce a C11 feature. I see that _Generic is already used in
> PPC...
> However, if we decide to add more use of it, then I think this should
> at
> minimum be documented in docs/misra/C-language-toolchain.rst (the
> more
> if we plan the macro is moved to common as Jan suggested).
>
> Cheers,
>
On 05.02.2024 16:32, Oleksii Kurochko wrote:
> From: Bobby Eshleman <bobbyeshleman@gmail.com>
>
> Additionally, this patch introduces macros in fence.h,
> which are utilized in atomic.h.
These are used in an earlier patch already, so either you want to
re-order the series, or you want to move that introduction ahead.
> --- /dev/null
> +++ b/xen/arch/riscv/include/asm/atomic.h
> @@ -0,0 +1,395 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Taken and modified from Linux.
> + *
> + * atomic##prefix##_*xchg_*(atomic##prefix##_t *v, c_t n) were updated to use
> + * __*xchg_generic()
> + *
> + * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
> + * Copyright (C) 2012 Regents of the University of California
> + * Copyright (C) 2017 SiFive
> + * Copyright (C) 2021 Vates SAS
> + */
> +
> +#ifndef _ASM_RISCV_ATOMIC_H
> +#define _ASM_RISCV_ATOMIC_H
> +
> +#include <xen/atomic.h>
> +#include <asm/cmpxchg.h>
> +#include <asm/fence.h>
> +#include <asm/io.h>
> +#include <asm/system.h>
> +
> +void __bad_atomic_size(void);
> +
> +static always_inline void read_atomic_size(const volatile void *p,
> + void *res,
> + unsigned int size)
> +{
> + switch ( size )
> + {
> + case 1: *(uint8_t *)res = readb(p); break;
> + case 2: *(uint16_t *)res = readw(p); break;
> + case 4: *(uint32_t *)res = readl(p); break;
> + case 8: *(uint32_t *)res = readq(p); break;
Why is it the MMIO primitives you use here, i.e. not read<X>_cpu()?
It's RAM you're accessing after all.
Also - no CONFIG_64BIT conditional here (like you have in the other
patch)?
> + default: __bad_atomic_size(); break;
> + }
> +}
> +
> +#define read_atomic(p) ({ \
> + union { typeof(*p) val; char c[0]; } x_; \
> + read_atomic_size(p, x_.c, sizeof(*p)); \
I'll be curious for how much longer gcc will tolerate this accessing
of a zero-length array, without issuing at least a warning. I'd
recommend using sizeof(*(p)) as the array dimension right away. (From
this not also the missing parentheses in what you have.)
> + x_.val; \
> +})
> +
> +#define write_atomic(p, x) \
> +({ \
> + typeof(*p) x__ = (x); \
> + switch ( sizeof(*p) ) \
> + { \
> + case 1: writeb((uint8_t)x__, p); break; \
> + case 2: writew((uint16_t)x__, p); break; \
> + case 4: writel((uint32_t)x__, p); break; \
> + case 8: writeq((uint64_t)x__, p); break; \
Are the casts actually necessary here?
> + default: __bad_atomic_size(); break; \
> + } \
> + x__; \
> +})
> +
> +#define add_sized(p, x) \
> +({ \
> + typeof(*(p)) x__ = (x); \
> + switch ( sizeof(*(p)) ) \
> + { \
> + case 1: writeb(read_atomic(p) + x__, p); break; \
> + case 2: writew(read_atomic(p) + x__, p); break; \
> + case 4: writel(read_atomic(p) + x__, p); break; \
> + default: __bad_atomic_size(); break; \
> + } \
> +})
> +
> +/*
> + * __unqual_scalar_typeof(x) - Declare an unqualified scalar type, leaving
> + * non-scalar types unchanged.
> + *
> + * Prefer C11 _Generic for better compile-times and simpler code. Note: 'char'
> + * is not type-compatible with 'signed char', and we define a separate case.
> + */
> +#define __scalar_type_to_expr_cases(type) \
> + unsigned type: (unsigned type)0, \
> + signed type: (signed type)0
> +
> +#define __unqual_scalar_typeof(x) typeof( \
> + _Generic((x), \
> + char: (char)0, \
> + __scalar_type_to_expr_cases(char), \
> + __scalar_type_to_expr_cases(short), \
> + __scalar_type_to_expr_cases(int), \
> + __scalar_type_to_expr_cases(long), \
> + __scalar_type_to_expr_cases(long long), \
> + default: (x)))
This isn't RISC-V specific, is it? In which case it wants moving to,
perhaps, xen/macros.h (and then also have the leading underscores
dropped).
> +#define READ_ONCE(x) (*(const volatile __unqual_scalar_typeof(x) *)&(x))
> +#define WRITE_ONCE(x, val) \
> + do { \
> + *(volatile typeof(x) *)&(x) = (val); \
> + } while (0)
In Xen we use ACCESS_ONCE(); any reason you need to introduce
{READ,WRITE}_ONCE() in addition? Without them, __unqual_scalar_typeof()
may then also not be needed (or, if there's a need to enhance it, may
then be needed for ACCESS_ONCE()). Which in turn raises the question
why only READ_ONCE() uses it here.
> +#define __atomic_acquire_fence() \
> + __asm__ __volatile__( RISCV_ACQUIRE_BARRIER "" ::: "memory" )
Missing blank here and ...
> +#define __atomic_release_fence() \
> + __asm__ __volatile__( RISCV_RELEASE_BARRIER "" ::: "memory" );
... here, and stray semicolon additionally just here.
> +static inline int atomic_read(const atomic_t *v)
> +{
> + return READ_ONCE(v->counter);
> +}
> +
> +static inline int _atomic_read(atomic_t v)
> +{
> + return v.counter;
> +}
> +
> +static inline void atomic_set(atomic_t *v, int i)
> +{
> + WRITE_ONCE(v->counter, i);
> +}
> +
> +static inline void _atomic_set(atomic_t *v, int i)
> +{
> + v->counter = i;
> +}
> +
> +static inline int atomic_sub_and_test(int i, atomic_t *v)
> +{
> + return atomic_sub_return(i, v) == 0;
> +}
> +
> +static inline void atomic_inc(atomic_t *v)
> +{
> + atomic_add(1, v);
> +}
> +
> +static inline int atomic_inc_return(atomic_t *v)
> +{
> + return atomic_add_return(1, v);
> +}
> +
> +static inline void atomic_dec(atomic_t *v)
> +{
> + atomic_sub(1, v);
> +}
> +
> +static inline int atomic_dec_return(atomic_t *v)
> +{
> + return atomic_sub_return(1, v);
> +}
> +
> +static inline int atomic_dec_and_test(atomic_t *v)
> +{
> + return atomic_sub_return(1, v) == 0;
> +}
> +
> +static inline int atomic_add_negative(int i, atomic_t *v)
> +{
> + return atomic_add_return(i, v) < 0;
> +}
> +
> +static inline int atomic_inc_and_test(atomic_t *v)
> +{
> + return atomic_add_return(1, v) == 0;
> +}
None of these look RISC-V-specific. Perhaps worth having something in
asm-generic/ that can be utilized here?
> +/*
> + * First, the atomic ops that have no ordering constraints and therefor don't
> + * have the AQ or RL bits set. These don't return anything, so there's only
> + * one version to worry about.
> + */
> +#define ATOMIC_OP(op, asm_op, I, asm_type, c_type, prefix) \
> +static inline \
> +void atomic##prefix##_##op(c_type i, atomic##prefix##_t *v) \
> +{ \
> + __asm__ __volatile__ ( \
> + " amo" #asm_op "." #asm_type " zero, %1, %0" \
> + : "+A" (v->counter) \
> + : "r" (I) \
> + : "memory" ); \
> +} \
> +
> +#define ATOMIC_OPS(op, asm_op, I) \
> + ATOMIC_OP (op, asm_op, I, w, int, )
So the last three parameters are to be ready to also support
atomic64, without actually doing so right now?
> +ATOMIC_OPS(add, add, i)
> +ATOMIC_OPS(sub, add, -i)
> +ATOMIC_OPS(and, and, i)
> +ATOMIC_OPS( or, or, i)
> +ATOMIC_OPS(xor, xor, i)
> +
> +#undef ATOMIC_OP
> +#undef ATOMIC_OPS
> +
> +/*
> + * Atomic ops that have ordered, relaxed, acquire, and release variants.
> + * There's two flavors of these: the arithmatic ops have both fetch and return
> + * versions, while the logical ops only have fetch versions.
> + */
I'm somewhat confused by the comment: It first talks of 4 variants, but
then says there are only 2 (arithmetic) or 1 (logical) ones.
> +#define ATOMIC_FETCH_OP(op, asm_op, I, asm_type, c_type, prefix) \
> +static inline \
> +c_type atomic##prefix##_fetch_##op##_relaxed(c_type i, \
> + atomic##prefix##_t *v) \
> +{ \
> + register c_type ret; \
> + __asm__ __volatile__ ( \
> + " amo" #asm_op "." #asm_type " %1, %2, %0" \
> + : "+A" (v->counter), "=r" (ret) \
> + : "r" (I) \
> + : "memory" ); \
> + return ret; \
> +} \
> +static inline \
> +c_type atomic##prefix##_fetch_##op(c_type i, atomic##prefix##_t *v) \
> +{ \
> + register c_type ret; \
> + __asm__ __volatile__ ( \
> + " amo" #asm_op "." #asm_type ".aqrl %1, %2, %0" \
> + : "+A" (v->counter), "=r" (ret) \
> + : "r" (I) \
> + : "memory" ); \
> + return ret; \
> +}
> +
> +#define ATOMIC_OP_RETURN(op, asm_op, c_op, I, asm_type, c_type, prefix) \
> +static inline \
> +c_type atomic##prefix##_##op##_return_relaxed(c_type i, \
> + atomic##prefix##_t *v) \
> +{ \
> + return atomic##prefix##_fetch_##op##_relaxed(i, v) c_op I; \
> +} \
> +static inline \
> +c_type atomic##prefix##_##op##_return(c_type i, atomic##prefix##_t *v) \
> +{ \
> + return atomic##prefix##_fetch_##op(i, v) c_op I; \
> +}
> +
> +#define ATOMIC_OPS(op, asm_op, c_op, I) \
> + ATOMIC_FETCH_OP( op, asm_op, I, w, int, ) \
> + ATOMIC_OP_RETURN(op, asm_op, c_op, I, w, int, )
> +
> +ATOMIC_OPS(add, add, +, i)
> +ATOMIC_OPS(sub, add, +, -i)
> +
> +#define atomic_add_return_relaxed atomic_add_return_relaxed
> +#define atomic_sub_return_relaxed atomic_sub_return_relaxed
> +#define atomic_add_return atomic_add_return
> +#define atomic_sub_return atomic_sub_return
> +
> +#define atomic_fetch_add_relaxed atomic_fetch_add_relaxed
> +#define atomic_fetch_sub_relaxed atomic_fetch_sub_relaxed
> +#define atomic_fetch_add atomic_fetch_add
> +#define atomic_fetch_sub atomic_fetch_sub
What are all of these #define-s (any yet more further down) about?
> +static inline int atomic_sub_if_positive(atomic_t *v, int offset)
> +{
> + int prev, rc;
> +
> + __asm__ __volatile__ (
> + "0: lr.w %[p], %[c]\n"
> + " sub %[rc], %[p], %[o]\n"
> + " bltz %[rc], 1f\n"
> + " sc.w.rl %[rc], %[rc], %[c]\n"
> + " bnez %[rc], 0b\n"
> + " fence rw, rw\n"
> + "1:\n"
> + : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
> + : [o]"r" (offset)
Nit: Blanks please between ] and ".
> --- /dev/null
> +++ b/xen/arch/riscv/include/asm/fence.h
> @@ -0,0 +1,8 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef _ASM_RISCV_FENCE_H
> +#define _ASM_RISCV_FENCE_H
> +
> +#define RISCV_ACQUIRE_BARRIER "\tfence r , rw\n"
> +#define RISCV_RELEASE_BARRIER "\tfence rw, w\n"
Seeing that another "fence rw, rw" appears in this patch, I'm now pretty
sure you want to add e.g. RISCV_FULL_BARRIER here as well.
Jan
On Tue, 2024-02-13 at 12:36 +0100, Jan Beulich wrote:
> On 05.02.2024 16:32, Oleksii Kurochko wrote:
> > From: Bobby Eshleman <bobbyeshleman@gmail.com>
> >
> > Additionally, this patch introduces macros in fence.h,
> > which are utilized in atomic.h.
>
> These are used in an earlier patch already, so either you want to
> re-order the series, or you want to move that introduction ahead.
>
> > --- /dev/null
> > +++ b/xen/arch/riscv/include/asm/atomic.h
> > @@ -0,0 +1,395 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Taken and modified from Linux.
> > + *
> > + * atomic##prefix##_*xchg_*(atomic##prefix##_t *v, c_t n) were
> > updated to use
> > + * __*xchg_generic()
> > + *
> > + * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
> > + * Copyright (C) 2012 Regents of the University of California
> > + * Copyright (C) 2017 SiFive
> > + * Copyright (C) 2021 Vates SAS
> > + */
> > +
> > +#ifndef _ASM_RISCV_ATOMIC_H
> > +#define _ASM_RISCV_ATOMIC_H
> > +
> > +#include <xen/atomic.h>
> > +#include <asm/cmpxchg.h>
> > +#include <asm/fence.h>
> > +#include <asm/io.h>
> > +#include <asm/system.h>
> > +
> > +void __bad_atomic_size(void);
> > +
> > +static always_inline void read_atomic_size(const volatile void *p,
> > + void *res,
> > + unsigned int size)
> > +{
> > + switch ( size )
> > + {
> > + case 1: *(uint8_t *)res = readb(p); break;
> > + case 2: *(uint16_t *)res = readw(p); break;
> > + case 4: *(uint32_t *)res = readl(p); break;
> > + case 8: *(uint32_t *)res = readq(p); break;
>
> Why is it the MMIO primitives you use here, i.e. not read<X>_cpu()?
> It's RAM you're accessing after all.
Legacy from Linux kernel. For some reason they wanted to have ordered
read/write access.
>
> Also - no CONFIG_64BIT conditional here (like you have in the other
> patch)?
Agree, it should be added.
>
> > + default: __bad_atomic_size(); break;
> > + }
> > +}
> > +
> > +#define read_atomic(p) ({ \
> > + union { typeof(*p) val; char c[0]; } x_; \
> > + read_atomic_size(p, x_.c, sizeof(*p)); \
>
> I'll be curious for how much longer gcc will tolerate this accessing
> of a zero-length array, without issuing at least a warning. I'd
> recommend using sizeof(*(p)) as the array dimension right away. (From
> this not also the missing parentheses in what you have.)
Thanks. I'll update that.
>
> > + x_.val; \
> > +})
> > +
> > +#define write_atomic(p, x) \
> > +({ \
> > + typeof(*p) x__ = (x); \
> > + switch ( sizeof(*p) ) \
> > + { \
> > + case 1: writeb((uint8_t)x__, p); break; \
> > + case 2: writew((uint16_t)x__, p); break; \
> > + case 4: writel((uint32_t)x__, p); break; \
> > + case 8: writeq((uint64_t)x__, p); break; \
>
> Are the casts actually necessary here?
Not really, we can drop them.
>
> > + default: __bad_atomic_size(); break; \
> > + } \
> > + x__; \
> > +})
> > +
> > +#define add_sized(p, x) \
> > +({ \
> > + typeof(*(p)) x__ = (x); \
> > + switch ( sizeof(*(p)) ) \
> > + { \
> > + case 1: writeb(read_atomic(p) + x__, p); break; \
> > + case 2: writew(read_atomic(p) + x__, p); break; \
> > + case 4: writel(read_atomic(p) + x__, p); break; \
> > + default: __bad_atomic_size(); break; \
> > + } \
> > +})
> > +
> > +/*
> > + * __unqual_scalar_typeof(x) - Declare an unqualified scalar
> > type, leaving
> > + * non-scalar types unchanged.
> > + *
> > + * Prefer C11 _Generic for better compile-times and simpler code.
> > Note: 'char'
> > + * is not type-compatible with 'signed char', and we define a
> > separate case.
> > + */
> > +#define __scalar_type_to_expr_cases(type) \
> > + unsigned type: (unsigned type)0, \
> > + signed type: (signed type)0
> > +
> > +#define __unqual_scalar_typeof(x) typeof( \
> > + _Generic((x), \
> > + char: (char)0, \
> > + __scalar_type_to_expr_cases(char), \
> > + __scalar_type_to_expr_cases(short), \
> > + __scalar_type_to_expr_cases(int), \
> > + __scalar_type_to_expr_cases(long), \
> > + __scalar_type_to_expr_cases(long long), \
> > + default: (x)))
>
> This isn't RISC-V specific, is it? In which case it wants moving to,
> perhaps, xen/macros.h (and then also have the leading underscores
> dropped).
No, at all. But this thing is only used in RISC-V part, but if it would
be better to move it to xen/macros.h I will happy to sent separate
patch.
>
> > +#define READ_ONCE(x) (*(const volatile __unqual_scalar_typeof(x)
> > *)&(x))
> > +#define WRITE_ONCE(x, val) \
> > + do { \
> > + *(volatile typeof(x) *)&(x) = (val); \
> > + } while (0)
>
> In Xen we use ACCESS_ONCE(); any reason you need to introduce
> {READ,WRITE}_ONCE() in addition? Without them,
> __unqual_scalar_typeof()
> may then also not be needed (or, if there's a need to enhance it, may
> then be needed for ACCESS_ONCE()). Which in turn raises the question
> why only READ_ONCE() uses it here.
Hmm, READ_ONCE() and WRITE_ONCE() can be dropped then, I'll switch
everything in my code to ACCESS_ONCE().
>
> > +#define __atomic_acquire_fence() \
> > + __asm__ __volatile__( RISCV_ACQUIRE_BARRIER "" ::: "memory" )
>
> Missing blank here and ...
>
> > +#define __atomic_release_fence() \
> > + __asm__ __volatile__( RISCV_RELEASE_BARRIER "" ::: "memory" );
>
> ... here, and stray semicolon additionally just here.
Thanks. I'll apply your comments to this part of code.
>
> > +static inline int atomic_read(const atomic_t *v)
> > +{
> > + return READ_ONCE(v->counter);
> > +}
> > +
> > +static inline int _atomic_read(atomic_t v)
> > +{
> > + return v.counter;
> > +}
> > +
> > +static inline void atomic_set(atomic_t *v, int i)
> > +{
> > + WRITE_ONCE(v->counter, i);
> > +}
> > +
> > +static inline void _atomic_set(atomic_t *v, int i)
> > +{
> > + v->counter = i;
> > +}
> > +
> > +static inline int atomic_sub_and_test(int i, atomic_t *v)
> > +{
> > + return atomic_sub_return(i, v) == 0;
> > +}
> > +
> > +static inline void atomic_inc(atomic_t *v)
> > +{
> > + atomic_add(1, v);
> > +}
> > +
> > +static inline int atomic_inc_return(atomic_t *v)
> > +{
> > + return atomic_add_return(1, v);
> > +}
> > +
> > +static inline void atomic_dec(atomic_t *v)
> > +{
> > + atomic_sub(1, v);
> > +}
> > +
> > +static inline int atomic_dec_return(atomic_t *v)
> > +{
> > + return atomic_sub_return(1, v);
> > +}
> > +
> > +static inline int atomic_dec_and_test(atomic_t *v)
> > +{
> > + return atomic_sub_return(1, v) == 0;
> > +}
> > +
> > +static inline int atomic_add_negative(int i, atomic_t *v)
> > +{
> > + return atomic_add_return(i, v) < 0;
> > +}
> > +
> > +static inline int atomic_inc_and_test(atomic_t *v)
> > +{
> > + return atomic_add_return(1, v) == 0;
> > +}
>
> None of these look RISC-V-specific. Perhaps worth having something in
> asm-generic/ that can be utilized here?
Looks like we can, at least, PPC has the similar definitions.
>
> > +/*
> > + * First, the atomic ops that have no ordering constraints and
> > therefor don't
> > + * have the AQ or RL bits set. These don't return anything, so
> > there's only
> > + * one version to worry about.
> > + */
> > +#define ATOMIC_OP(op, asm_op, I, asm_type, c_type, prefix) \
> > +static inline \
> > +void atomic##prefix##_##op(c_type i, atomic##prefix##_t *v) \
> > +{ \
> > + __asm__ __volatile__ ( \
> > + " amo" #asm_op "." #asm_type " zero, %1, %0" \
> > + : "+A" (v->counter) \
> > + : "r" (I) \
> > + : "memory" ); \
> > +} \
> > +
> > +#define ATOMIC_OPS(op, asm_op, I) \
> > + ATOMIC_OP (op, asm_op, I, w, int, )
>
> So the last three parameters are to be ready to also support
> atomic64, without actually doing so right now?
Yes, it is ready to support.
>
> > +ATOMIC_OPS(add, add, i)
> > +ATOMIC_OPS(sub, add, -i)
> > +ATOMIC_OPS(and, and, i)
> > +ATOMIC_OPS( or, or, i)
> > +ATOMIC_OPS(xor, xor, i)
> > +
> > +#undef ATOMIC_OP
> > +#undef ATOMIC_OPS
> > +
> > +/*
> > + * Atomic ops that have ordered, relaxed, acquire, and release
> > variants.
> > + * There's two flavors of these: the arithmatic ops have both
> > fetch and return
> > + * versions, while the logical ops only have fetch versions.
> > + */
>
> I'm somewhat confused by the comment: It first talks of 4 variants,
> but
> then says there are only 2 (arithmetic) or 1 (logical) ones.
Probably they mean that usually they have 4 variants, but it was
implemented only 2 (arith) and 1 (logical).
>
> > +#define ATOMIC_FETCH_OP(op, asm_op, I, asm_type, c_type,
> > prefix) \
> > +static
> > inline \
> > +c_type atomic##prefix##_fetch_##op##_relaxed(c_type
> > i, \
> > + atomic##prefix##_t
> > *v) \
> > +{
> > \
> > + register c_type
> > ret; \
> > + __asm__ __volatile__
> > ( \
> > + " amo" #asm_op "." #asm_type " %1, %2,
> > %0" \
> > + : "+A" (v->counter), "=r"
> > (ret) \
> > + : "r"
> > (I) \
> > + : "memory"
> > ); \
> > + return
> > ret; \
> > +}
> > \
> > +static
> > inline \
> > +c_type atomic##prefix##_fetch_##op(c_type i, atomic##prefix##_t
> > *v) \
> > +{
> > \
> > + register c_type
> > ret; \
> > + __asm__ __volatile__
> > ( \
> > + " amo" #asm_op "." #asm_type ".aqrl %1, %2,
> > %0" \
> > + : "+A" (v->counter), "=r"
> > (ret) \
> > + : "r"
> > (I) \
> > + : "memory"
> > ); \
> > + return
> > ret; \
> > +}
> > +
> > +#define ATOMIC_OP_RETURN(op, asm_op, c_op, I, asm_type, c_type,
> > prefix) \
> > +static
> > inline \
> > +c_type atomic##prefix##_##op##_return_relaxed(c_type
> > i, \
> > + atomic##prefix##_t
> > *v) \
> > +{
> > \
> > + return atomic##prefix##_fetch_##op##_relaxed(i, v) c_op
> > I; \
> > +}
> > \
> > +static
> > inline \
> > +c_type atomic##prefix##_##op##_return(c_type i, atomic##prefix##_t
> > *v) \
> > +{
> > \
> > + return atomic##prefix##_fetch_##op(i, v) c_op
> > I; \
> > +}
> > +
> > +#define ATOMIC_OPS(op, asm_op, c_op,
> > I) \
> > + ATOMIC_FETCH_OP( op, asm_op, I, w, int,
> > ) \
> > + ATOMIC_OP_RETURN(op, asm_op, c_op, I, w, int, )
> > +
> > +ATOMIC_OPS(add, add, +, i)
> > +ATOMIC_OPS(sub, add, +, -i)
> > +
> > +#define atomic_add_return_relaxed atomic_add_return_relaxed
> > +#define atomic_sub_return_relaxed atomic_sub_return_relaxed
> > +#define atomic_add_return atomic_add_return
> > +#define atomic_sub_return atomic_sub_return
> > +
> > +#define atomic_fetch_add_relaxed atomic_fetch_add_relaxed
> > +#define atomic_fetch_sub_relaxed atomic_fetch_sub_relaxed
> > +#define atomic_fetch_add atomic_fetch_add
> > +#define atomic_fetch_sub atomic_fetch_sub
>
> What are all of these #define-s (any yet more further down) about?
>
> > +static inline int atomic_sub_if_positive(atomic_t *v, int offset)
> > +{
> > + int prev, rc;
> > +
> > + __asm__ __volatile__ (
> > + "0: lr.w %[p], %[c]\n"
> > + " sub %[rc], %[p], %[o]\n"
> > + " bltz %[rc], 1f\n"
> > + " sc.w.rl %[rc], %[rc], %[c]\n"
> > + " bnez %[rc], 0b\n"
> > + " fence rw, rw\n"
> > + "1:\n"
> > + : [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
> > + : [o]"r" (offset)
>
> Nit: Blanks please between ] and ".
Thanks. I'll update that.
>
> > --- /dev/null
> > +++ b/xen/arch/riscv/include/asm/fence.h
> > @@ -0,0 +1,8 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +#ifndef _ASM_RISCV_FENCE_H
> > +#define _ASM_RISCV_FENCE_H
> > +
> > +#define RISCV_ACQUIRE_BARRIER "\tfence r , rw\n"
> > +#define RISCV_RELEASE_BARRIER "\tfence rw, w\n"
>
> Seeing that another "fence rw, rw" appears in this patch, I'm now
> pretty
> sure you want to add e.g. RISCV_FULL_BARRIER here as well.
It makes sense. I'll do that. Thanks.
>
> Jan
On 14.02.2024 13:11, Oleksii wrote:
> On Tue, 2024-02-13 at 12:36 +0100, Jan Beulich wrote:
>> On 05.02.2024 16:32, Oleksii Kurochko wrote:
>>> --- /dev/null
>>> +++ b/xen/arch/riscv/include/asm/atomic.h
>>> @@ -0,0 +1,395 @@
>>> +/* SPDX-License-Identifier: GPL-2.0-only */
>>> +/*
>>> + * Taken and modified from Linux.
>>> + *
>>> + * atomic##prefix##_*xchg_*(atomic##prefix##_t *v, c_t n) were
>>> updated to use
>>> + * __*xchg_generic()
>>> + *
>>> + * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
>>> + * Copyright (C) 2012 Regents of the University of California
>>> + * Copyright (C) 2017 SiFive
>>> + * Copyright (C) 2021 Vates SAS
>>> + */
>>> +
>>> +#ifndef _ASM_RISCV_ATOMIC_H
>>> +#define _ASM_RISCV_ATOMIC_H
>>> +
>>> +#include <xen/atomic.h>
>>> +#include <asm/cmpxchg.h>
>>> +#include <asm/fence.h>
>>> +#include <asm/io.h>
>>> +#include <asm/system.h>
>>> +
>>> +void __bad_atomic_size(void);
>>> +
>>> +static always_inline void read_atomic_size(const volatile void *p,
>>> + void *res,
>>> + unsigned int size)
>>> +{
>>> + switch ( size )
>>> + {
>>> + case 1: *(uint8_t *)res = readb(p); break;
>>> + case 2: *(uint16_t *)res = readw(p); break;
>>> + case 4: *(uint32_t *)res = readl(p); break;
>>> + case 8: *(uint32_t *)res = readq(p); break;
>>
>> Why is it the MMIO primitives you use here, i.e. not read<X>_cpu()?
>> It's RAM you're accessing after all.
> Legacy from Linux kernel. For some reason they wanted to have ordered
> read/write access.
Wants expressing in a comment then, or at the very least in the patch
description.
Jan
© 2016 - 2026 Red Hat, Inc.