From: Andy Lutomirski <luto@kernel.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
X86 ML <x86@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86: use register variable to get stack pointer value
Date: Fri, 29 Sep 2017 11:37:52 -0700 [thread overview]
Message-ID: <CALCETrUZN=bEbBYwohM+oALu+MG7-SJUAG5_Fr4ppNVQ_SFMAg@mail.gmail.com> (raw)
In-Reply-To: <20170929153828.rtxwllhsjgiaeaos@treble>
On Fri, Sep 29, 2017 at 8:38 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> On Fri, Sep 29, 2017 at 05:15:36PM +0300, Andrey Ryabinin wrote:
>> Currently we use current_stack_pointer() function to get the value
>> of the stack pointer register. Since commit f5caf621ee35
>> ("x86/asm: Fix inline asm call constraints for Clang") we have stack
>> register variable declared. It can be used instead of current_stack_pointer()
>> function which allows to optimize away some excessive "mov %rsp, %<dst>"
>> instructions:
>>
>> -mov %rsp,%rdx
>> -sub %rdx,%rax
>> -cmp $0x3fff,%rax
>> -ja ffffffff810722fd <ist_begin_non_atomic+0x2d>
>>
>> +sub %rsp,%rax
>> +cmp $0x3fff,%rax
>> +ja ffffffff810722fa <ist_begin_non_atomic+0x2a>
>>
>> Remove current_stack_pointer(), rename __asm_call_sp to current_stack_pointer
>> and use it instead of removed function.
>>
>> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
>
> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Ok with me. As an alternative, you could leave it as
current_stack_pointer(), but either way is fine.
next prev parent reply other threads:[~2017-09-29 18:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-29 14:15 [PATCH] x86: use register variable to get stack pointer value Andrey Ryabinin
2017-09-29 15:38 ` Josh Poimboeuf
2017-09-29 18:37 ` Andy Lutomirski [this message]
2017-09-29 19:16 ` Josh Poimboeuf
2017-09-29 20:15 ` [tip:x86/urgent] x86/asm: Use " tip-bot for Andrey Ryabinin
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