From: Alexey Dobriyan <adobriyan@gmail.com>
To: x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com
Cc: linux-kernel@vger.kernel.org, bp@suse.de
Subject: [PATCH 4/5] x86_64: clobber "cc" in inlined clear_page()
Date: Wed, 26 Apr 2017 21:34:05 +0300 [thread overview]
Message-ID: <20170426183405.GD5069@avx2> (raw)
In-Reply-To: <20170426183047.GC5069@avx2>
Both REP variants clobber flags because of "xor eax, eax" instructions.
While they can be changed to "mov eax, 0", generic version probably
can not because it has to do comparison at some point.
And it is kind of not worth it to not clobber flags anyway.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---
arch/x86/include/asm/page_64.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/include/asm/page_64.h
+++ b/arch/x86/include/asm/page_64.h
@@ -46,7 +46,7 @@ static inline void clear_page(void *page)
clear_page_rep_stosb, X86_FEATURE_ERMS,
"=D" (page),
"0" (page)
- : "memory", "rax", "rcx");
+ : "cc", "memory", "rax", "rcx");
}
void copy_page_mov(void *to, void *from);
next prev parent reply other threads:[~2017-04-26 18:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-26 18:23 [PATCH 1/5] x86_64: use REP MOVSB in copy_page() Alexey Dobriyan
2017-04-26 18:28 ` [PATCH 2/5] x86_64: inline copy_page() at call site Alexey Dobriyan
2017-04-26 18:30 ` [PATCH 3/5] x86_64: rename clear_page() and copy_user() variants Alexey Dobriyan
2017-04-26 18:34 ` Alexey Dobriyan [this message]
2017-04-26 18:35 ` [PATCH 5/5] x86_64: garbage collect headers in clear_page.S Alexey Dobriyan
2017-05-05 16:58 ` [PATCH 3/5] x86_64: rename clear_page() and copy_user() variants Borislav Petkov
2017-04-28 21:04 ` [PATCH 2/5] x86_64: inline copy_page() at call site Borislav Petkov
2017-05-02 11:49 ` Alexey Dobriyan
2017-05-02 11:59 ` Borislav Petkov
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