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From: Pavel Machek <pavel@ucw.cz>
To: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Brian Gerst <brgerst@gmail.com>, Ingo Molnar <mingo@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>, X86 ML <x86@kernel.org>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Denys Vlasenko <dvlasenk@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] x86: General protection fault after STR (32 bit systems only)
Date: Sat, 13 Jun 2015 16:20:05 +0200	[thread overview]
Message-ID: <20150613142005.GA29207@amd> (raw)
In-Reply-To: <CAK1hOcPvst1+vT_3_m0t7HZF_fz9zjDd_azyWj6n0Ma-qY3ZQQ@mail.gmail.com>

On Sat 2015-06-13 00:45:29, Denys Vlasenko wrote:
> On Fri, Jun 12, 2015 at 5:48 PM, Brian Gerst <brgerst@gmail.com> wrote:
> > If you follow the convoluted flow of the calls in this file,
> > ...
> 
> Speaking of which. It is indeed quite bad.
> 
> For one, saved_eip is only ever set to point to ret_point:
> 
> ENTRY(saved_eip)        .long   0
> ...
> 
>         movl    $ret_point, saved_eip
> 
> and it has just a single user, where an indirect jump
> through it is performed:
> 
>         # jump to place where we left off
>         movl    saved_eip, %eax
>         jmp     *%eax
> 
> No comments why it is so.
> 
> All this seems to be equivalent to trivial
> 
>         # jump to place where we left off
>         jmp     ret_point
> 
> Am I missing something?

I don't think so. Its just that slowdown was not bad enough tofix it.

...patch would be welcome, and even better if you could check the issue
on 64-bit kernel, too...
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

  reply	other threads:[~2015-06-13 14:20 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-06-11 23:45 [PATCH] x86: General protection fault after STR (32 bit systems only) Srinivas Pandruvada
2015-06-12  6:07 ` Ingo Molnar
2015-06-12  6:48   ` Andy Lutomirski
2015-06-12  7:15     ` Ingo Molnar
2015-06-12  7:41   ` Andy Lutomirski
2015-06-12  7:50     ` Ingo Molnar
2015-06-12  8:15       ` H. Peter Anvin
2015-06-12  8:36         ` Ingo Molnar
2015-06-12 15:48           ` Brian Gerst
2015-06-12 18:11             ` Andy Lutomirski
2015-06-12 18:31               ` Srinivas Pandruvada
2015-06-13  7:00                 ` Ingo Molnar
2015-06-12 22:45             ` Denys Vlasenko
2015-06-13 14:20               ` Pavel Machek [this message]
2015-06-13  7:03             ` Ingo Molnar
2015-06-13 18:23               ` Andy Lutomirski
2015-06-13 21:30                 ` Brian Gerst
2015-06-14  6:56                   ` [PATCH] x86: Load __USER_DS into DS/ES after resume Ingo Molnar
2015-06-14  7:03                     ` Pavel Machek
     [not found]                     ` <CA+55aFzB9dYidEf_7Hs47FOF7WPPJnJQwj_RiwL--c5Gb1uqyw@mail.gmail.com>
2015-06-14  7:49                       ` [PATCH v2] " Ingo Molnar
2015-06-14  8:57                         ` Pavel Machek
2015-06-14 14:22                           ` Brian Gerst
2015-06-15 16:12                         ` Srinivas Pandruvada
2015-06-16  9:13                         ` Pavel Machek
2015-06-16 21:40                           ` Rafael J. Wysocki
2015-06-17  8:59                             ` x86: allow using different kernel version for 32-bit, too Pavel Machek
2015-06-18  9:13                             ` [PATCH v2] x86: Load __USER_DS into DS/ES after resume Ingo Molnar
2015-06-22 14:06                               ` Rafael J. Wysocki
2015-06-12 16:15   ` [PATCH] x86: General protection fault after STR (32 bit systems only) Srinivas Pandruvada
2015-06-13  7:15     ` [PATCH, DEBUG] x86/32: Add small delay after resume Ingo Molnar
2015-06-15 16:10       ` Srinivas Pandruvada
2015-06-16 21:33         ` H. Peter Anvin
2015-06-16 22:25           ` Srinivas Pandruvada
2015-06-17 16:33           ` Konrad Rzeszutek Wilk
2015-06-17 17:22             ` H. Peter Anvin
2015-06-17 18:29               ` Konrad Rzeszutek Wilk

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