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Date:   Fri, 15 Sep 2023 11:25:02 -0000
From:   "tip-bot2 for Uros Bizjak" <tip-bot2@linutronix.de>
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Subject: [tip: x86/asm] x86/percpu: Define {raw,this}_cpu_try_cmpxchg{64,128}
Cc:     Uros Bizjak <ubizjak@gmail.com>, Ingo Molnar <mingo@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>, x86@kernel.org,
        linux-kernel@vger.kernel.org
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The following commit has been merged into the x86/asm branch of tip:

Commit-ID:     54cd971c6f4461fb6b178579751788bf4f64dfca
Gitweb:        https://git.kernel.org/tip/54cd971c6f4461fb6b178579751788bf4f64dfca
Author:        Uros Bizjak <ubizjak@gmail.com>
AuthorDate:    Wed, 06 Sep 2023 20:58:44 +02:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Fri, 15 Sep 2023 13:16:35 +02:00

x86/percpu: Define {raw,this}_cpu_try_cmpxchg{64,128}

Define target-specific {raw,this}_cpu_try_cmpxchg64() and
{raw,this}_cpu_try_cmpxchg128() macros. These definitions override
the generic fallback definitions and enable target-specific
optimized implementations.

Several places in mm/slub.o improve from e.g.:

    53bc:	48 8d 4f 40          	lea    0x40(%rdi),%rcx
    53c0:	48 89 fa             	mov    %rdi,%rdx
    53c3:	49 8b 5c 05 00       	mov    0x0(%r13,%rax,1),%rbx
    53c8:	4c 89 e8             	mov    %r13,%rax
    53cb:	49 8d 30             	lea    (%r8),%rsi
    53ce:	e8 00 00 00 00       	call   53d3 <...>
			53cf: R_X86_64_PLT32	this_cpu_cmpxchg16b_emu-0x4
    53d3:	48 31 d7             	xor    %rdx,%rdi
    53d6:	4c 31 e8             	xor    %r13,%rax
    53d9:	48 09 c7             	or     %rax,%rdi
    53dc:	75 ae                	jne    538c <...>

to:

    53bc:	48 8d 4a 40          	lea    0x40(%rdx),%rcx
    53c0:	49 8b 1c 07          	mov    (%r15,%rax,1),%rbx
    53c4:	4c 89 f8             	mov    %r15,%rax
    53c7:	48 8d 37             	lea    (%rdi),%rsi
    53ca:	e8 00 00 00 00       	call   53cf <...>
			53cb: R_X86_64_PLT32	this_cpu_cmpxchg16b_emu-0x4
    53cf:	75 bb                	jne    538c <...>

reducing the size of mm/slub.o by 80 bytes:

   text    data     bss     dec     hex filename
  39758    5337    4208   49303    c097 slub-new.o
  39838    5337    4208   49383    c0e7 slub-old.o

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230906185941.53527-1-ubizjak@gmail.com
---
 arch/x86/include/asm/percpu.h | 67 ++++++++++++++++++++++++++++++++++-
 1 file changed, 67 insertions(+)

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 34734d7..4c36419 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -237,12 +237,47 @@ do {									\
 
 #define raw_cpu_cmpxchg64(pcp, oval, nval)	percpu_cmpxchg64_op(8,         , pcp, oval, nval)
 #define this_cpu_cmpxchg64(pcp, oval, nval)	percpu_cmpxchg64_op(8, volatile, pcp, oval, nval)
+
+#define percpu_try_cmpxchg64_op(size, qual, _var, _ovalp, _nval)	\
+({									\
+	bool success;							\
+	u64 *_oval = (u64 *)(_ovalp);					\
+	union {								\
+		u64 var;						\
+		struct {						\
+			u32 low, high;					\
+		};							\
+	} old__, new__;							\
+									\
+	old__.var = *_oval;						\
+	new__.var = _nval;						\
+									\
+	asm qual (ALTERNATIVE("leal %P[var], %%esi; call this_cpu_cmpxchg8b_emu", \
+			      "cmpxchg8b " __percpu_arg([var]), X86_FEATURE_CX8) \
+		  CC_SET(z)						\
+		  : CC_OUT(z) (success),				\
+		    [var] "+m" (_var),					\
+		    "+a" (old__.low),					\
+		    "+d" (old__.high)					\
+		  : "b" (new__.low),					\
+		    "c" (new__.high)					\
+		  : "memory", "esi");					\
+	if (unlikely(!success))						\
+		*_oval = old__.var;					\
+	likely(success);						\
+})
+
+#define raw_cpu_try_cmpxchg64(pcp, ovalp, nval)		percpu_try_cmpxchg64_op(8,         , pcp, ovalp, nval)
+#define this_cpu_try_cmpxchg64(pcp, ovalp, nval)	percpu_try_cmpxchg64_op(8, volatile, pcp, ovalp, nval)
 #endif
 
 #ifdef CONFIG_X86_64
 #define raw_cpu_cmpxchg64(pcp, oval, nval)	percpu_cmpxchg_op(8,         , pcp, oval, nval);
 #define this_cpu_cmpxchg64(pcp, oval, nval)	percpu_cmpxchg_op(8, volatile, pcp, oval, nval);
 
+#define raw_cpu_try_cmpxchg64(pcp, ovalp, nval)		percpu_try_cmpxchg_op(8,         , pcp, ovalp, nval);
+#define this_cpu_try_cmpxchg64(pcp, ovalp, nval)	percpu_try_cmpxchg_op(8, volatile, pcp, ovalp, nval);
+
 #define percpu_cmpxchg128_op(size, qual, _var, _oval, _nval)		\
 ({									\
 	union {								\
@@ -269,6 +304,38 @@ do {									\
 
 #define raw_cpu_cmpxchg128(pcp, oval, nval)	percpu_cmpxchg128_op(16,         , pcp, oval, nval)
 #define this_cpu_cmpxchg128(pcp, oval, nval)	percpu_cmpxchg128_op(16, volatile, pcp, oval, nval)
+
+#define percpu_try_cmpxchg128_op(size, qual, _var, _ovalp, _nval)	\
+({									\
+	bool success;							\
+	u128 *_oval = (u128 *)(_ovalp);					\
+	union {								\
+		u128 var;						\
+		struct {						\
+			u64 low, high;					\
+		};							\
+	} old__, new__;							\
+									\
+	old__.var = *_oval;						\
+	new__.var = _nval;						\
+									\
+	asm qual (ALTERNATIVE("leaq %P[var], %%rsi; call this_cpu_cmpxchg16b_emu", \
+			      "cmpxchg16b " __percpu_arg([var]), X86_FEATURE_CX16) \
+		  CC_SET(z)						\
+		  : CC_OUT(z) (success),				\
+		    [var] "+m" (_var),					\
+		    "+a" (old__.low),					\
+		    "+d" (old__.high)					\
+		  : "b" (new__.low),					\
+		    "c" (new__.high)					\
+		  : "memory", "rsi");					\
+	if (unlikely(!success))						\
+		*_oval = old__.var;					\
+	likely(success);						\
+})
+
+#define raw_cpu_try_cmpxchg128(pcp, ovalp, nval)	percpu_try_cmpxchg128_op(16,         , pcp, ovalp, nval)
+#define this_cpu_try_cmpxchg128(pcp, ovalp, nval)	percpu_try_cmpxchg128_op(16, volatile, pcp, ovalp, nval)
 #endif
 
 /*