From: "H. Peter Anvin" <hpa@zytor.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>,
Denys Vlasenko <vda.linux@googlemail.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Brian Gerst <brgerst@gmail.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
Ingo Molnar <mingo@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
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/asm/entry/32: Restore %ss before SYSRETL if necessary
Date: Thu, 23 Apr 2015 15:31:49 -0700 [thread overview]
Message-ID: <553972D5.2070104@zytor.com> (raw)
In-Reply-To: <CALCETrVX_O+vu+GJXJKJa7w83DnKn0nrjp2_9xtNdhEJW79XQA@mail.gmail.com>
On 04/23/2015 03:29 PM, Andy Lutomirski wrote:
>>
>> Yes, the NULL SS is a special thing in 64-bit mode. I agree that
>> context-switching it is probably the way to go; it should be cheap
>> enough. We might even be able to conditionalize it on an X86_BUG_ flag.
>
> I still don't see why context switches are a better place than just
> before sysret, but I could be convinced.
>
Because there are way more sysrets than context switches, and Linux is
particularly sensitive to system call latency, by design.
-hpa
next prev parent reply other threads:[~2015-04-23 22:32 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-23 12:34 [PATCH] x86/asm/entry/32: Restore %ss before SYSRETL if necessary Denys Vlasenko
2015-04-23 15:22 ` Linus Torvalds
2015-04-23 15:50 ` Andy Lutomirski
2015-04-23 16:05 ` Linus Torvalds
2015-04-23 16:11 ` Borislav Petkov
2015-04-23 16:06 ` Brian Gerst
2015-04-23 16:13 ` Linus Torvalds
2015-04-23 16:27 ` Andy Lutomirski
2015-04-23 20:01 ` Denys Vlasenko
2015-04-23 21:10 ` Borislav Petkov
2015-04-23 21:37 ` H. Peter Anvin
2015-04-23 21:46 ` Borislav Petkov
2015-04-23 22:29 ` Andy Lutomirski
2015-04-23 22:31 ` H. Peter Anvin [this message]
2015-04-23 22:38 ` Andy Lutomirski
2015-04-23 22:52 ` H. Peter Anvin
2015-04-23 22:55 ` Andy Lutomirski
2015-04-23 23:04 ` Linus Torvalds
2015-04-23 23:22 ` Denys Vlasenko
2015-04-24 0:59 ` H. Peter Anvin
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