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From: Ingo Molnar <mingo@kernel.org>
To: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
	Oleg Nesterov <oleg@redhat.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Alexei Starovoitov <ast@plumgrid.com>,
	Will Drewry <wad@chromium.org>, Kees Cook <keescook@chromium.org>,
	X86 ML <x86@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/4] x86: save user rsp in pt_regs->sp on SYSCALL64 fastpath
Date: Mon, 16 Mar 2015 10:44:28 +0100	[thread overview]
Message-ID: <20150316094428.GA32738@gmail.com> (raw)
In-Reply-To: <CAK1hOcMTRhO3hhqD0Ft6qJ-NYn9uZ7tcTKxJB1=nRR-3fkbYEw@mail.gmail.com>


* Denys Vlasenko <vda.linux@googlemail.com> wrote:

> > - but making it slower without really good reasons isn't good.
> 
> The thinking here is that cleaning up entry.S is a good reason.
> 
> We won't do anything which would slow it down by, say, 5%,
> but one cycle may be considered acceptable loss.

Ok, so I've applied this particular cleanup, in the hope that we can 
recover those cycles on the now cleaner base.

If that doesn't work out then we can still re-introduce this 
complication and see its maintainability in isolation, on a clean 
base.

Thanks,

	Ingo

  reply	other threads:[~2015-03-16  9:44 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-09 18:39 [PATCH 0/4 v2] x86: entry_64.S: steps towards simpler iret frame handling Denys Vlasenko
2015-03-09 18:39 ` [PATCH 1/4] x86: save r11 into pt_regs->flags on SYSCALL64 fastpath Denys Vlasenko
2015-03-09 20:02   ` Andy Lutomirski
2015-03-16 12:04   ` [tip:x86/asm] x86/asm/entry/64: Save R11 into pt_regs-> flags " tip-bot for Denys Vlasenko
2015-03-09 18:39 ` [PATCH 3/4] x86: save user rsp in pt_regs->sp " Denys Vlasenko
2015-03-09 20:11   ` Andy Lutomirski
2015-03-09 20:32     ` Denys Vlasenko
2015-03-09 20:43       ` Andy Lutomirski
2015-03-10 12:51   ` Ingo Molnar
2015-03-10 13:10     ` Andy Lutomirski
2015-03-10 13:18     ` Denys Vlasenko
2015-03-10 13:20       ` Andy Lutomirski
2015-03-10 13:26         ` Ingo Molnar
2015-03-10 13:21       ` Ingo Molnar
2015-03-10 13:26         ` Andy Lutomirski
2015-03-10 14:00           ` Denys Vlasenko
2015-03-10 14:02             ` Andy Lutomirski
2015-03-10 14:09               ` Denys Vlasenko
2015-03-10 13:28         ` Ingo Molnar
2015-03-10 13:50         ` Denys Vlasenko
2015-03-16  9:44           ` Ingo Molnar [this message]
2015-03-16 12:05   ` [tip:x86/asm] x86/asm/entry/64: Save user RSP in pt_regs-> sp " tip-bot for Denys Vlasenko
2015-03-10  6:00 ` [PATCH 0/4 v2] x86: entry_64.S: steps towards simpler iret frame handling Ingo Molnar

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