From: David Woodhouse <dwmw2@infradead.org>
To: Borislav Petkov <bp@alien8.de>, KarimAllah Ahmed <karahmed@amazon.com>
Cc: arjan@linux.intel.com, tglx@linutronix.de, karahmed@amazon.de,
x86@kernel.org, linux-kernel@vger.kernel.org,
tim.c.chen@linux.intel.com, peterz@infradead.org,
pbonzini@redhat.com, ak@linux.intel.com,
torvalds@linux-foundation.org, gregkh@linux-foundation.org
Subject: Re: [PATCH v2 5/8] x86/speculation: Add basic support for IBPB
Date: Sun, 21 Jan 2018 19:31:00 +0000 [thread overview]
Message-ID: <1516563060.9814.52.camel@infradead.org> (raw)
In-Reply-To: <20180121190145.uuk3xizxejckth5s@pd.tnic>
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On Sun, 2018-01-21 at 20:01 +0100, Borislav Petkov wrote:
>
> so execution runs directly into the MSR write and the JMP is gone.
>
> So I don't see indirect branches anywhere...
Wait until the wind changes.
Congratulations, you've just turned a potential GCC missed optimisation
into a kernel bug. We don't *care* that it's unlikely that GCC will
miss that optimisation. The point is that it doesn't *have* to do it,
and we don't *check*.
cf. https://lkml.org/lkml/2018/1/12/176
... after which Peter went off and implemented that check, which is all
fine and dandy but let's not rely on backporting that too.
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next prev parent reply other threads:[~2018-01-21 19:31 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-21 9:49 [PATCH v2 0/8] Speculation Control feature support, IBPB David Woodhouse
2018-01-21 9:49 ` [PATCH v2 1/8] x86/cpufeatures: Add Intel feature bits for Speculation Control David Woodhouse
2018-01-21 10:17 ` Ingo Molnar
2018-01-21 9:49 ` [PATCH v2 2/8] x86/cpufeatures: Add AMD feature bits for Prediction Command David Woodhouse
2018-01-21 17:50 ` Tom Lendacky
2018-01-21 18:01 ` Andrew Cooper
2018-01-22 14:31 ` Tom Lendacky
2018-01-22 14:33 ` Andrew Cooper
2018-01-21 9:49 ` [PATCH v2 3/8] x86/msr: Add definitions for new speculation control MSRs David Woodhouse
2018-01-21 13:06 ` Jiri Slaby
2018-01-21 13:27 ` David Woodhouse
2018-01-21 9:49 ` [PATCH v2 4/8] x86/pti: Do not enable PTI on fixed Intel processors David Woodhouse
2018-01-21 13:38 ` Borislav Petkov
2018-01-21 9:49 ` [PATCH v2 5/8] x86/speculation: Add basic support for IBPB David Woodhouse
2018-01-21 10:26 ` Ingo Molnar
2018-01-21 18:06 ` Borislav Petkov
2018-01-21 18:29 ` KarimAllah Ahmed
2018-01-21 19:01 ` Borislav Petkov
2018-01-21 19:31 ` David Woodhouse [this message]
2018-01-21 19:37 ` Andrew Cooper
2018-01-21 20:04 ` David Woodhouse
2018-01-21 20:19 ` Andrew Cooper
2018-01-21 21:25 ` David Woodhouse
2018-01-21 19:53 ` Borislav Petkov
2018-01-21 18:54 ` David Woodhouse
2018-01-21 19:04 ` Borislav Petkov
2018-01-21 19:31 ` David Woodhouse
2018-01-21 19:54 ` Borislav Petkov
2018-01-21 20:07 ` David Woodhouse
2018-01-21 20:17 ` Borislav Petkov
2018-01-21 9:49 ` [PATCH v2 6/8] x86/kvm: Add IBPB support David Woodhouse
2018-01-21 18:06 ` Tom Lendacky
2018-01-21 9:49 ` [PATCH v2 7/8] x86/speculation: Use Indirect Branch Prediction Barrier in context switch David Woodhouse
2018-01-21 9:49 ` [PATCH v2 8/8] x86/mm: Only flush indirect branches when switching into non dumpable process David Woodhouse
2018-01-21 10:33 ` Ingo Molnar
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