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[PATCH] x86/asm: Remove semicolon from LOCK prefix

To: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>

From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Date: Fri, 28 Feb 2025 22:12:13 +0000

Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>

Delivery-date: Fri, 28 Feb 2025 22:14:33 +0000

List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

Most of Xen's LOCK prefixes are already without semicolon, but we have a few still remaining in the tree. As noted in the Linux patch, this adversly affects size/inlining decisions, and prevents the assembler from diagnosing some classes of error. No functional change. Link: https://lore.kernel.org/lkml/20250228085149.2478245-1-ubizjak@xxxxxxxxx/ Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> --- CC: Jan Beulich <JBeulich@xxxxxxxx> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx> It really does change inlining decisions. Bloat-o-meter reports: add/remove: 1/1 grow/shrink: 7/1 up/down: 691/-247 (444) Function old new delta cpupool_do_sysctl 1737 1945 +208 kexec_do_unload.isra - 150 +150 kexec_load_slot 396 502 +106 poll_timer_fn 37 104 +67 cpupool_unassign_cpu_finish 376 427 +51 cpupool_create_pool 82 130 +48 cpupool_assign_cpu_locked 346 394 +48 panic 170 183 +13 do_kexec_op_internal 2117 2022 -95 kexec_swap_images 152 - -152 e.g. poll_timer_fn() previously tailcalled vcpu_unblock(), but now takes a copy of it. --- xen/arch/x86/include/asm/atomic.h | 16 ++++++++-------- xen/arch/x86/include/asm/bitops.h | 12 ++++++------ xen/arch/x86/include/asm/spinlock.h | 2 +- 3 files changed, 15 insertions(+), 15 deletions(-) diff --git a/xen/arch/x86/include/asm/atomic.h b/xen/arch/x86/include/asm/atomic.h index 16bd0ebfd763..ed4e09a50329 100644 --- a/xen/arch/x86/include/asm/atomic.h +++ b/xen/arch/x86/include/asm/atomic.h @@ -115,7 +115,7 @@ static inline int atomic_cmpxchg(atomic_t *v, int old, int new) static inline void atomic_add(int i, atomic_t *v) { asm volatile ( - "lock; addl %1,%0" + "lock addl %1,%0" : "=m" (*(volatile int *)&v->counter) : "ir" (i), "m" (*(volatile int *)&v->counter) ); } @@ -128,7 +128,7 @@ static inline int atomic_add_return(int i, atomic_t *v) static inline void atomic_sub(int i, atomic_t *v) { asm volatile ( - "lock; subl %1,%0" + "lock subl %1,%0" : "=m" (*(volatile int *)&v->counter) : "ir" (i), "m" (*(volatile int *)&v->counter) ); } @@ -142,7 +142,7 @@ static inline int atomic_sub_and_test(int i, atomic_t *v) { bool c; - asm volatile ( "lock; subl %[i], %[counter]\n\t" + asm volatile ( "lock subl %[i], %[counter]\n\t" ASM_FLAG_OUT(, "setz %[zf]\n\t") : [counter] "+m" (*(volatile int *)&v->counter), [zf] ASM_FLAG_OUT("=@ccz", "=qm") (c) @@ -154,7 +154,7 @@ static inline int atomic_sub_and_test(int i, atomic_t *v) static inline void atomic_inc(atomic_t *v) { asm volatile ( - "lock; incl %0" + "lock incl %0" : "=m" (*(volatile int *)&v->counter) : "m" (*(volatile int *)&v->counter) ); } @@ -168,7 +168,7 @@ static inline int atomic_inc_and_test(atomic_t *v) { bool c; - asm volatile ( "lock; incl %[counter]\n\t" + asm volatile ( "lock incl %[counter]\n\t" ASM_FLAG_OUT(, "setz %[zf]\n\t") : [counter] "+m" (*(volatile int *)&v->counter), [zf] ASM_FLAG_OUT("=@ccz", "=qm") (c) @@ -180,7 +180,7 @@ static inline int atomic_inc_and_test(atomic_t *v) static inline void atomic_dec(atomic_t *v) { asm volatile ( - "lock; decl %0" + "lock decl %0" : "=m" (*(volatile int *)&v->counter) : "m" (*(volatile int *)&v->counter) ); } @@ -194,7 +194,7 @@ static inline int atomic_dec_and_test(atomic_t *v) { bool c; - asm volatile ( "lock; decl %[counter]\n\t" + asm volatile ( "lock decl %[counter]\n\t" ASM_FLAG_OUT(, "setz %[zf]\n\t") : [counter] "+m" (*(volatile int *)&v->counter), [zf] ASM_FLAG_OUT("=@ccz", "=qm") (c) @@ -207,7 +207,7 @@ static inline int atomic_add_negative(int i, atomic_t *v) { bool c; - asm volatile ( "lock; addl %[i], %[counter]\n\t" + asm volatile ( "lock addl %[i], %[counter]\n\t" ASM_FLAG_OUT(, "sets %[sf]\n\t") : [counter] "+m" (*(volatile int *)&v->counter), [sf] ASM_FLAG_OUT("=@ccs", "=qm") (c) diff --git a/xen/arch/x86/include/asm/bitops.h b/xen/arch/x86/include/asm/bitops.h index 39e37f1cbe55..bb9d75646023 100644 --- a/xen/arch/x86/include/asm/bitops.h +++ b/xen/arch/x86/include/asm/bitops.h @@ -32,7 +32,7 @@ */ static inline void set_bit(int nr, volatile void *addr) { - asm volatile ( "lock; btsl %1,%0" + asm volatile ( "lock btsl %1,%0" : "+m" (ADDR) : "Ir" (nr) : "memory"); } #define set_bit(nr, addr) ({ \ @@ -73,7 +73,7 @@ static inline void constant_set_bit(int nr, void *addr) */ static inline void clear_bit(int nr, volatile void *addr) { - asm volatile ( "lock; btrl %1,%0" + asm volatile ( "lock btrl %1,%0" : "+m" (ADDR) : "Ir" (nr) : "memory"); } #define clear_bit(nr, addr) ({ \ @@ -140,7 +140,7 @@ static inline void constant_change_bit(int nr, void *addr) */ static inline void change_bit(int nr, volatile void *addr) { - asm volatile ( "lock; btcl %1,%0" + asm volatile ( "lock btcl %1,%0" : "+m" (ADDR) : "Ir" (nr) : "memory"); } #define change_bit(nr, addr) ({ \ @@ -160,7 +160,7 @@ static inline int test_and_set_bit(int nr, volatile void *addr) { int oldbit; - asm volatile ( "lock; btsl %[nr], %[addr]\n\t" + asm volatile ( "lock btsl %[nr], %[addr]\n\t" ASM_FLAG_OUT(, "sbbl %[old], %[old]\n\t") : [old] ASM_FLAG_OUT("=@ccc", "=r") (oldbit), [addr] "+m" (ADDR) : [nr] "Ir" (nr) : "memory" ); @@ -206,7 +206,7 @@ static inline int test_and_clear_bit(int nr, volatile void *addr) { int oldbit; - asm volatile ( "lock; btrl %[nr], %[addr]\n\t" + asm volatile ( "lock btrl %[nr], %[addr]\n\t" ASM_FLAG_OUT(, "sbbl %[old], %[old]\n\t") : [old] ASM_FLAG_OUT("=@ccc", "=r") (oldbit), [addr] "+m" (ADDR) : [nr] "Ir" (nr) : "memory" ); @@ -266,7 +266,7 @@ static inline int test_and_change_bit(int nr, volatile void *addr) { int oldbit; - asm volatile ( "lock; btcl %[nr], %[addr]\n\t" + asm volatile ( "lock btcl %[nr], %[addr]\n\t" ASM_FLAG_OUT(, "sbbl %[old], %[old]\n\t") : [old] ASM_FLAG_OUT("=@ccc", "=r") (oldbit), [addr] "+m" (ADDR) : [nr] "Ir" (nr) : "memory" ); diff --git a/xen/arch/x86/include/asm/spinlock.h b/xen/arch/x86/include/asm/spinlock.h index 56f60957522a..834e8c580ebd 100644 --- a/xen/arch/x86/include/asm/spinlock.h +++ b/xen/arch/x86/include/asm/spinlock.h @@ -3,7 +3,7 @@ #define _raw_read_unlock(l) \ BUILD_BUG_ON(sizeof((l)->lock) != 4); /* Clang doesn't support %z in asm. */ \ - asm volatile ( "lock; decl %0" : "+m" ((l)->lock) :: "memory" ) + asm volatile ( "lock decl %0" : "+m" ((l)->lock) :: "memory" ) /* * On x86 the only reordering is of reads with older writes. In the base-commit: e95dc03717b8ae00de2a0b41b88905af6170b210 -- 2.39.5

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