Re: [tip:x86/pti] x86/speculation: Use IBRS if available before calling into firmware
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- Subject: Re: [tip:x86/pti] x86/speculation: Use IBRS if available before calling into firmware
- From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
- Date: Mon, 12 Feb 2018 14:06:40 +0100
- Cc: Ingo Molnar <mingo@xxxxxxxxxx>, Thomas Mingarelli <thomas.mingarelli@xxxxxxx>, hpa@xxxxxxxxx, tglx@xxxxxxxxxxxxx, torvalds@xxxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-tip-commits@xxxxxxxxxxxxxxx, Dave Hansen <dave@xxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Arjan van de Ven <arjan@xxxxxxxxxxxxx>
- In-reply-to: <1518438439.6606.36.camel@infradead.org>
- References: <1518362359-1005-1-git-send-email-dwmw@amazon.co.uk> <tip-670c3e8da87fa4046a55077b1409cf250865a203@git.kernel.org> <20180212102211.cdrrqqd4hdw7xu5y@gmail.com> <20180212115002.GI25181@hirez.programming.kicks-ass.net> <1518438439.6606.36.camel@infradead.org>
- User-agent: Mutt/1.9.2 (2017-12-15)
On Mon, Feb 12, 2018 at 12:27:19PM +0000, David Woodhouse wrote:
> On Mon, 2018-02-12 at 12:50 +0100, Peter Zijlstra wrote:
> > Wait, we're doing firmware from NMI? That sounds like a _REALLY_ bad
> > idea.
>
> And spin_lock_irqsave() too. Which is probably why I missed the fact
> that this was being called in NMI context.
>
> Yay for HP and their persistent attempts to "value subtract" in their
> firmware offerings.
>
> I'm tempted to drop that part of the patch and declare that if you're
> using this driver, the potential for stray branch prediction when you
> call into the firmware from the NMI handler is the *least* of your
> problems.
We should probably mark it BROKEN or something, or move it into staging.
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