linux-kernel - Re: GPF in intel_pmu_lbr_reset() with qemu -cpu host

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Message-ID: <8761n7nryi.fsf@tassilo.jf.intel.com>
Date:	Fri, 21 Mar 2014 14:48:37 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Peter Wu <peter@...ensteyn.nl>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: GPF in intel_pmu_lbr_reset() with qemu -cpu host

"H. Peter Anvin" <hpa@...or.com> writes:
>
> That's why at least to some extent The Right Thing is not to try to
> pretend to be a CPU you don't even know how to emulate.
>
> But again, that has its own issues, too, mostly with userspace
> optimization, and making the Linux code more resilient wouldn't hurt.
> In that sense #GP(0) is *much* better than 0: it unambiguously gives an
> error to work with.

That means we could just throw rdmsr() away and it would be completely
replaced with rdmsr_safe(). But then that will likely cause all kinds
of problems with how to handle these errors and where and how to handle
these exceptions.

I much prefer just to fix KVM. I cannot think of any case
where 0 would cause a major issue.

After all it's virtualization not "rewrite complete kernel for it"

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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