All of lore.kernel.org
 help / color / mirror / Atom feed
From: hpa@zytor.com
To: Linus Torvalds <torvalds@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Julien Thierry <julien.thierry@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Ingo Molnar <mingo@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	James Morse <james.morse@arm.com>,
	valentin.schneider@arm.com, Brian Gerst <brgerst@gmail.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Andrew Lutomirski <luto@kernel.org>,
	Borislav Petkov <bp@alien8.de>,
	Denys Vlasenko <dvlasenk@redhat.com>,
	Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
	Dmitry Vyukov <dvyukov@google.com>,
	Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 01/25] x86: Make SMAP 64-bit only
Date: Thu, 21 Mar 2019 10:12:35 -0700	[thread overview]
Message-ID: <168D2D76-419B-46F1-B3D5-76CB1F1C252F@zytor.com> (raw)
In-Reply-To: <CAHk-=wguWBY_W8-M0vSCae538mAY2vQtkrdNbZX4T8rvAYxPxg@mail.gmail.com>

On March 18, 2019 11:10:22 AM PDT, Linus Torvalds <torvalds@linux-foundation.org> wrote:
>On Mon, Mar 18, 2019 at 10:51 AM Peter Zijlstra <peterz@infradead.org>
>wrote:
>>
>> How about I do a patch that schedules EFLAGS for both 32bit and
>64bit,
>> mark this for backporting to infinity.
>>
>> And then at the end, after the objtool-ac bits land, I do a patch
>> removing the EFLAGS scheduling for x86_64.
>
>Sounds sane to me.
>
>And we can make it AC-conditional if it's actually shown to be visible
>from a performance standpoint.
>
>But iirc pushf/popf isn't really that expensive - in fact I think it's
>pretty cheap when system flags don't change. Which would be the common
>case unless you'd also make the popf do the irq restore part and
>simply make finish_lock_switch() re-enable irq's by doing an
>irqrestore?
>
>I think popf is like 20 cycles or something (and pushf is just single
>cycles). Probably not worth worrying about in the task switch context.
>
>                 Linus

Yes, the problem isn't scheduling per se but the risk of hiding problems.
-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

  reply	other threads:[~2019-03-21 17:13 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-18 15:38 [PATCH 00/25] objtool: UACCESS validation v4 Peter Zijlstra
2019-03-18 15:38 ` [PATCH 01/25] x86: Make SMAP 64-bit only Peter Zijlstra
2019-03-18 16:58   ` Linus Torvalds
2019-03-18 17:36     ` Peter Zijlstra
2019-03-18 17:51       ` Peter Zijlstra
2019-03-18 18:10         ` Linus Torvalds
2019-03-21 17:12           ` hpa [this message]
2019-03-21 17:25           ` Denys Vlasenko
2019-03-21 18:18             ` hpa
2019-03-21 21:03               ` Peter Zijlstra
2019-03-21 18:21             ` Linus Torvalds
2019-03-19 11:16   ` [PATCH 01/25] sched/x86: Save [ER]FLAGS on context switch Peter Zijlstra
2019-03-18 15:38 ` [PATCH 02/25] tracing: Improve "if" macro code generation Peter Zijlstra
2019-03-18 17:41   ` Steven Rostedt
2019-03-18 23:37   ` Josh Poimboeuf
2019-03-19 10:11     ` Peter Zijlstra
2019-03-20 11:18   ` David Laight
2019-03-20 17:26     ` Linus Torvalds
2019-03-20 17:37       ` David Laight
2019-03-20 17:38         ` Linus Torvalds
2019-03-20 18:18       ` Steven Rostedt
2019-05-09 13:00       ` Steven Rostedt
2019-05-09 16:51         ` Linus Torvalds
2019-05-09 18:29           ` Steven Rostedt
2019-05-09 18:45             ` Josh Poimboeuf
2019-05-09 18:47               ` Josh Poimboeuf
2019-05-09 18:48                 ` Randy Dunlap
2019-05-09 18:57                   ` Josh Poimboeuf
2019-05-09 19:06               ` Steven Rostedt
2019-05-09 19:28                 ` Steven Rostedt
2019-05-09 19:44                   ` Linus Torvalds
2019-03-18 15:38 ` [PATCH 03/25] x86/ia32: Fix ia32_restore_sigcontext AC leak Peter Zijlstra
2019-03-18 15:38 ` [PATCH 04/25] i915,uaccess: Fix redundant CLAC Peter Zijlstra
2019-03-18 15:38 ` [PATCH 05/25] x86/uaccess: Move copy_user_handle_tail into asm Peter Zijlstra
2019-03-18 15:38 ` [PATCH 06/25] x86/uaccess: Fix up the fixup Peter Zijlstra
2019-03-18 15:38 ` [PATCH 07/25] x86/nospec,objtool: Introduce ANNOTATE_IGNORE_ALTERNATIVE Peter Zijlstra
2019-03-18 15:38 ` [PATCH 08/25] x86/uaccess,xen: Suppress SMAP warnings Peter Zijlstra
2019-03-18 15:38 ` [PATCH 09/25] x86/uaccess: Always inline user_access_begin() Peter Zijlstra
2019-03-18 15:38 ` [PATCH 10/25] x86/uaccess,signal: Fix AC=1 bloat Peter Zijlstra
2019-03-18 15:38 ` [PATCH 11/25] x86/uaccess: Introduce user_access_{save,restore}() Peter Zijlstra
2019-03-18 15:38 ` [PATCH 12/25] x86/smap: Ditch __stringify() Peter Zijlstra
2019-03-18 15:38 ` [PATCH 13/25] x86/uaccess,kasan: Fix KASAN vs SMAP Peter Zijlstra
2019-03-18 15:38 ` [PATCH 14/25] x86/uaccess,ubsan: Fix UBSAN " Peter Zijlstra
2019-03-18 15:38 ` [PATCH 15/25] x86/uaccess,ftrace: Fix ftrace_likely_update() " Peter Zijlstra
2019-03-18 15:38 ` [PATCH 16/25] x86/uaccess,kcov: Disable stack protector Peter Zijlstra
2019-03-18 15:38 ` [PATCH 17/25] objtool: Set insn->func for alternatives Peter Zijlstra
2019-03-18 15:38 ` [PATCH 18/25] objtool: Handle function aliases Peter Zijlstra
2019-03-18 15:38 ` [PATCH 19/25] objtool: Rewrite add_ignores() Peter Zijlstra
2019-03-18 15:39 ` [PATCH 20/25] objtool: Add --backtrace support Peter Zijlstra
2019-03-18 15:39 ` [PATCH 21/25] objtool: Rewrite alt->skip_orig Peter Zijlstra
2019-03-18 15:39 ` [PATCH 22/25] objtool: Fix sibling call detection Peter Zijlstra
2019-03-18 15:39 ` [PATCH 23/25] objtool: Add UACCESS validation Peter Zijlstra
2019-03-18 23:51   ` Josh Poimboeuf
2019-05-07 11:52   ` Peter Zijlstra
2019-03-18 15:39 ` [PATCH 24/25] objtool: uaccess PUSHF/POPF support Peter Zijlstra
2019-03-18 15:39 ` [PATCH 25/25] objtool: Add Direction Flag validation Peter Zijlstra
2019-03-18 23:57 ` [PATCH 00/25] objtool: UACCESS validation v4 Josh Poimboeuf
2019-03-19 11:20   ` Peter Zijlstra
2019-03-19 11:17 ` [PATCH 26/25] sched/x86_64: Don't save flags on context switch Peter Zijlstra

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=168D2D76-419B-46F1-B3D5-76CB1F1C252F@zytor.com \
    --to=hpa@zytor.com \
    --cc=bp@alien8.de \
    --cc=brgerst@gmail.com \
    --cc=catalin.marinas@arm.com \
    --cc=dvlasenk@redhat.com \
    --cc=dvyukov@google.com \
    --cc=james.morse@arm.com \
    --cc=jpoimboe@redhat.com \
    --cc=julien.thierry@arm.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@amacapital.net \
    --cc=luto@kernel.org \
    --cc=mingo@kernel.org \
    --cc=peterz@infradead.org \
    --cc=rostedt@goodmis.org \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    --cc=valentin.schneider@arm.com \
    --cc=will.deacon@arm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.