Re: [tip:perfcounters/core] perf_counter: x86: Fix call-chain support to use NMI-safe methods
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- Subject: Re: [tip:perfcounters/core] perf_counter: x86: Fix call-chain support to use NMI-safe methods
- From: "H. Peter Anvin" <hpa@xxxxxxxxx>
- Date: Tue, 16 Jun 2009 08:22:55 -0700
- Cc: Ingo Molnar <mingo@xxxxxxx>, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, mingo@xxxxxxxxxx, paulus@xxxxxxxxx, acme@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, penberg@xxxxxxxxxxxxxx, vegard.nossum@xxxxxxxxx, efault@xxxxxx, jeremy@xxxxxxxx, npiggin@xxxxxxx, tglx@xxxxxxxxxxxxx, linux-tip-commits@xxxxxxxxxxxxxxx
- In-reply-to: <20090616141956.GB6541@Krystal>
- References: <20090615213429.GD12919@Krystal> <4A36BF61.10901@xxxxxxxxx> <20090615215420.GE12919@Krystal> <4A36C953.8060906@xxxxxxxxx> <20090615223038.GA15903@Krystal> <4A36CCFC.8070908@xxxxxxxxx> <20090615224908.GA16661@Krystal> <4A36F520.6020604@xxxxxxxxx> <20090616030522.GA22162@Krystal> <20090616083343.GD16229@xxxxxxx> <20090616141956.GB6541@Krystal>
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Mathieu Desnoyers wrote:
>
> With respect to cr2, yes, this is the only window we care about.
> However, the rest of vmalloc_fault() must be audited for other non
> nmi-suitable data structure use (e.g. "current"), which I did in the
> past.
>
> My intent was just to respond to Peter's concerns by showing that the
> part of page fault handler which needs to be NMI-reentrant is really not
> that big.
>
Even if that is true now, you want it to be true for all future time,
and all to support an out-of-tree piece of code. All of this is
virtually impossible to test for without said out-of-tree piece of code,
so I will object to it anyway.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
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