From: Denys Vlasenko <vda.linux@googlemail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>,
Andy Lutomirski <luto@amacapital.net>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.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>,
"the arch/x86 maintainers" <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86: entry_32.S: change ESPFIX test to not touch PT_OLDSS(%esp)
Date: Mon, 9 Mar 2015 17:28:26 +0100 [thread overview]
Message-ID: <CAK1hOcNmfy3RS20t-+Pmn+KFtoYM+RqyCx=LgfcHaaXnzF1M5w@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFzck8nuV06AZhhFXgUQEsujZCtufw0jY4iswJUggh6ruA@mail.gmail.com>
On Mon, Mar 9, 2015 at 5:08 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Mon, Mar 9, 2015 at 7:05 AM, Denys Vlasenko <dvlasenk@redhat.com> wrote:
>> New:
>> 1e6: 0f ba 64 24 38 11 btl $0x11,0x38(%esp)
>
> btl? Really?
>
> Why isn't that just
>
> testb $2,0x3a(%esp)
>
> which is both smaller and quite a bit faster on older machines.
Ok. (I thought people won't be happy about this.)
> Or just at least *partially* do what we used to do, and make it all be
>
> movb PT_EFLAGS+2(%esp),%al
> andb $2,%al
> orb PT_CS(%esp),%al
> testb $3,%al
> je restore_nocheck
These insns must run serially. 4 cycles.
test
branch
test
branch
can execute both test/branch'es out-of-order in parallel.
2 cycles.
next prev parent reply other threads:[~2015-03-09 16:28 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-09 14:05 [PATCH] x86: entry_32.S: change ESPFIX test to not touch PT_OLDSS(%esp) Denys Vlasenko
2015-03-09 14:18 ` Andy Lutomirski
2015-03-09 15:00 ` Denys Vlasenko
2015-03-09 15:09 ` Andy Lutomirski
2015-03-09 19:31 ` Denys Vlasenko
2015-03-09 15:13 ` Ingo Molnar
2015-03-09 15:18 ` Andy Lutomirski
2015-03-09 15:47 ` Steven Rostedt
2015-03-09 15:54 ` Ingo Molnar
2015-03-09 16:08 ` Linus Torvalds
2015-03-09 16:28 ` Denys Vlasenko [this message]
2015-03-09 16:44 ` Linus Torvalds
2015-03-09 17:44 ` H. Peter Anvin
2015-03-09 19:13 ` Andy Lutomirski
2015-03-09 19:26 ` H. Peter Anvin
2015-03-09 19:51 ` Andy Lutomirski
2015-03-09 17:42 ` H. Peter Anvin
2015-03-09 17:45 ` Andy Lutomirski
2015-03-09 17:59 ` Linus Torvalds
2015-03-09 18:04 ` Andy Lutomirski
2015-03-09 18:16 ` Linus Torvalds
2015-03-09 18:32 ` Denys Vlasenko
2015-03-09 18:36 ` Andy Lutomirski
2015-03-10 6:25 ` Ingo Molnar
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