Re: [PATCH urgent v2] x86, asm: Disable opportunistic SYSRET if regs->flags has TF set
From: Ingo Molnar
Date: Thu Apr 02 2015 - 12:08:51 EST
* Denys Vlasenko <dvlasenk@xxxxxxxxxx> wrote:
> On 04/02/2015 02:59 PM, Denys Vlasenko wrote:
> > On 04/02/2015 02:31 PM, Ingo Molnar wrote:
> >> - we can optimize in a more directed fashion - like here
> >> ... while the downsides are:
> >> - more code
> >> - a (small) chance of a fix going to one path while not the other.
> >> How much extra code would it be?
> > A screenful or two.
> I took a stab at it:
> text data bss dec hex filename
> 12530 0 0 12530 30f2 entry_64.o2
> 12562 0 0 12562 3112 entry_64.o
> The patch does two steps:
> (1) copy-pastes "retint_swapgs:" code into syscall handling code,
> the copy is under "syscall_return:" label.
> (2) remove "opportunistic sysret" code from "retint_swapgs" code block,
> since now it won't be reached by syscall return. This in fact removes
> most of the code in question.
> Lightly run-tested so far.
> Ingo, do you want this in a proper patch form?
Yeah, that looks good to me (only lightly reviewed).
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