From: Rik van Riel <riel@surriel.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: X86 ML <x86@kernel.org>, Borislav Petkov <bp@alien8.de>,
Jann Horn <jannh@google.com>, LKML <linux-kernel@vger.kernel.org>,
stable <stable@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Nadav Amit <nadav.amit@gmail.com>
Subject: Re: [PATCH] x86/nmi: Fix some races in NMI uaccess
Date: Tue, 28 Aug 2018 09:50:53 -0400 [thread overview]
Message-ID: <9f09dcbfa27004fc69dccf8039857f06438018f5.camel@surriel.com> (raw)
In-Reply-To: <CALCETrUMeV=P89msPuVuiWEw-MdZQZ9t0rTMgY8P91Q8tQvnXQ@mail.gmail.com>
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On Mon, 2018-08-27 at 19:10 -0700, Andy Lutomirski wrote:
> On Mon, Aug 27, 2018 at 6:31 PM, Rik van Riel <riel@surriel.com>
> wrote:
>
> > What is special about this path wrt nmi_uaccess_ok that is
> > not also true for the need_flush branch right above it?
> >
> > What am I missing?
>
> Nothing. My patch is buggy. ETOLITTLESLEEP.
>
> I could drop this part of the patch entirely. Or I could drop the
> loaded_mm->pgd == __va(read_cr3_pa() check and instead make sure that
> loaded_mm is NULL at any point at which loaded_mm might not match
> CR3.
> The latter will be faster in any (hypothetical) virtualization
> environment where CR3 reads trap. I don't know if we have any such
> cases where perf works and we care about performance, though.
Moving that loaded_mm = NULL assignment up a few
lines, so it comes before the "if (need_flush)"
test and covers both branches should cover that,
indeed.
--
All Rights Reversed.
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next prev parent reply other threads:[~2018-08-28 13:51 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-27 23:04 [PATCH] x86/nmi: Fix some races in NMI uaccess Andy Lutomirski
2018-08-27 23:12 ` Jann Horn
2018-08-27 23:25 ` Andy Lutomirski
2018-08-27 23:34 ` Jann Horn
2018-08-28 1:31 ` Rik van Riel
2018-08-28 2:10 ` Andy Lutomirski
2018-08-28 13:50 ` Rik van Riel [this message]
2018-08-28 17:56 ` [PATCH v2] " Rik van Riel
2018-08-29 3:46 ` Andy Lutomirski
2018-08-29 15:17 ` Rik van Riel
2018-08-29 15:36 ` Andy Lutomirski
2018-08-29 15:49 ` Rik van Riel
2018-08-29 16:14 ` Andy Lutomirski
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