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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v6 10/20] xen/riscv: introduce atomic.h
Initially the patch was introduced by Bobby, who takes the header from
Linux kernel.
The following changes were done on top of Linux kernel header:
- atomic##prefix##_*xchg_*(atomic##prefix##_t *v, c_t n) were updated
to use__*xchg_generic()
- drop casts in write_atomic() as they are unnecessary
- drop introduction of WRITE_ONCE() and READ_ONCE().
Xen provides ACCESS_ONCE()
- remove zero-length array access in read_atomic()
- drop defines similar to pattern
- #define atomic_add_return_relaxed atomic_add_return_relaxed
- move not RISC-V specific functions to asm-generic/atomics-ops.h
- drop atomic##prefix##_{cmp}xchg_{release, aquire, release}() as they
are not used in Xen.
- update the defintion of atomic##prefix##_{cmp}xchg according to
{cmp}xchg() implementation in Xen.
Signed-off-by: Bobby Eshleman <bobbyeshleman@xxxxxxxxx>
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in V6:
- drop atomic##prefix##_{cmp}xchg_{release, aquire, relaxed} as they aren't
used
by Xen
- code style fixes.
- %s/__asm__ __volatile__/asm volatile
- add explanational comments.
- move inclusion of "#include <asm-generic/atomic-ops.h>" further down in
atomic.h
header.
---
Changes in V5:
- fence.h changes were moved to separate patch as patches related to io.h and
cmpxchg.h,
which are dependecies for this patch, also needed changes in fence.h
- remove accessing of zero-length array
- drops cast in write_atomic()
- drop introduction of WRITE_ONCE() and READ_ONCE().
- drop defines similar to pattern #define atomic_add_return_relaxed
atomic_add_return_relaxed
- Xen code style fixes
- move not RISC-V specific functions to asm-generic/atomics-ops.h
---
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 | 263 +++++++++++++++++++++++++++
xen/include/asm-generic/atomic-ops.h | 97 ++++++++++
2 files changed, 360 insertions(+)
create mode 100644 xen/arch/riscv/include/asm/atomic.h
create mode 100644 xen/include/asm-generic/atomic-ops.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..4964821f3a
--- /dev/null
+++ b/xen/arch/riscv/include/asm/atomic.h
@@ -0,0 +1,263 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Taken and modified from Linux.
+ *
+ * The following changes were done:
+ * - * atomic##prefix##_*xchg_*(atomic##prefix##_t *v, c_t n) were updated
+ * to use__*xchg_generic()
+ * - drop casts in write_atomic() as they are unnecessary
+ * - drop introduction of WRITE_ONCE() and READ_ONCE().
+ * Xen provides ACCESS_ONCE()
+ * - remove zero-length array access in read_atomic()
+ * - drop defines similar to pattern
+ * #define atomic_add_return_relaxed atomic_add_return_relaxed
+ * - move not RISC-V specific functions to asm-generic/atomics-ops.h
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Copyright (C) 2012 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ * Copyright (C) 2024 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);
+
+/*
+ * Legacy from Linux kernel. For some reason they wanted to have ordered
+ * read/write access. Thereby read* is used instead of read<X>_cpu()
+ */
+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[sizeof(*(p))]; } 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(x__, p); break; \
+ case 2: writew(x__, p); break; \
+ case 4: writel(x__, p); break; \
+ case 8: writeq(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; \
+ case 8: writeq(read_atomic(p) + x__, p); break; \
+ default: __bad_atomic_size(); break; \
+ } \
+})
+
+#define __atomic_acquire_fence() \
+ asm volatile ( RISCV_ACQUIRE_BARRIER "" ::: "memory" )
+
+#define __atomic_release_fence() \
+ asm volatile ( RISCV_RELEASE_BARRIER "" ::: "memory" )
+
+/*
+ * 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" ); \
+} \
+
+/*
+ * Only CONFIG_GENERIC_ATOMIC64=y was ported to Xen that is the reason why
+ * last argument for ATOMIC_OP isn't used.
+ */
+#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
+
+#include <asm-generic/atomic-ops.h>
+
+/*
+ * 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; \
+}
+
+/*
+ * Only CONFIG_GENERIC_ATOMIC64=y was ported to Xen that is the reason why
+ * last argument of ATOMIC_FETCH_OP, ATOMIC_OP_RETURN isn't used.
+ */
+#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)
+
+#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)
+
+#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"
+ RISCV_FULL_BARRIER
+ "1:\n"
+ : [p] "=&r" (prev), [rc] "=&r" (rc), [c] "+A" (v->counter)
+ : [a] "r" (a), [u] "r" (u)
+ : "memory");
+ return prev;
+}
+
+/*
+ * atomic_{cmp,}xchg is required to have exactly the same ordering semantics as
+ * {cmp,}xchg and the operations that return.
+ */
+#define ATOMIC_OP(c_t, prefix, size) \
+static inline \
+c_t atomic##prefix##_xchg(atomic##prefix##_t *v, c_t n) \
+{ \
+ return __xchg(&(v->counter), n, size); \
+} \
+static inline \
+c_t atomic##prefix##_cmpxchg(atomic##prefix##_t *v, c_t o, c_t n) \
+{ \
+ return __cmpxchg(&v->counter, o, n, size); \
+}
+
+#define ATOMIC_OPS() \
+ ATOMIC_OP(int, , 4)
+
+ATOMIC_OPS()
+
+#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;
+}
+
+#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/include/asm-generic/atomic-ops.h
b/xen/include/asm-generic/atomic-ops.h
new file mode 100644
index 0000000000..da1ea5aac2
--- /dev/null
+++ b/xen/include/asm-generic/atomic-ops.h
@@ -0,0 +1,97 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * The header provides default implementations for every xen/atomic.h-provided
+ * forward inline declaration that can be synthesized from other atomic
+ * functions.
+ */
+#ifndef _ASM_GENERIC_ATOMIC_OPS_H_
+#define _ASM_GENERIC_ATOMIC_OPS_H_
+
+#include <xen/atomic.h>
+#include <xen/lib.h>
+
+#ifndef ATOMIC_READ
+static inline int atomic_read(const atomic_t *v)
+{
+ return ACCESS_ONCE(v->counter);
+}
+#endif
+
+#ifndef _ATOMIC_READ
+static inline int _atomic_read(atomic_t v)
+{
+ return v.counter;
+}
+#endif
+
+#ifndef ATOMIC_SET
+static inline void atomic_set(atomic_t *v, int i)
+{
+ ACCESS_ONCE(v->counter) = i;
+}
+#endif
+
+#ifndef _ATOMIC_SET
+static inline void _atomic_set(atomic_t *v, int i)
+{
+ v->counter = i;
+}
+#endif
+
+#ifndef ATOMIC_SUB_AND_TEST
+static inline int atomic_sub_and_test(int i, atomic_t *v)
+{
+ return atomic_sub_return(i, v) == 0;
+}
+#endif
+
+#ifndef ATOMIC_INC
+static inline void atomic_inc(atomic_t *v)
+{
+ atomic_add(1, v);
+}
+#endif
+
+#ifndef ATOMIC_INC_RETURN
+static inline int atomic_inc_return(atomic_t *v)
+{
+ return atomic_add_return(1, v);
+}
+#endif
+
+#ifndef ATOMIC_DEC
+static inline void atomic_dec(atomic_t *v)
+{
+ atomic_sub(1, v);
+}
+#endif
+
+#ifndef ATOMIC_DEC_RETURN
+static inline int atomic_dec_return(atomic_t *v)
+{
+ return atomic_sub_return(1, v);
+}
+#endif
+
+#ifndef ATOMIC_DEC_AND_TEST
+static inline int atomic_dec_and_test(atomic_t *v)
+{
+ return atomic_sub_return(1, v) == 0;
+}
+#endif
+
+#ifndef ATOMIC_ADD_NEGATIVE
+static inline int atomic_add_negative(int i, atomic_t *v)
+{
+ return atomic_add_return(i, v) < 0;
+}
+#endif
+
+#ifndef ATOMIC_INC_AND_TEST
+static inline int atomic_inc_and_test(atomic_t *v)
+{
+ return atomic_add_return(1, v) == 0;
+}
+#endif
+
+#endif /* _ASM_GENERIC_ATOMIC_OPS_H_ */
--
2.43.0
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