From: "H. Peter Anvin" <hpa@zytor.com>
To: Andi Kleen <ak@linux.intel.com>
Cc: Peter Wu <peter@lekensteyn.nl>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: GPF in intel_pmu_lbr_reset() with qemu -cpu host
Date: Fri, 21 Mar 2014 14:41:47 -0700 [thread overview]
Message-ID: <532CB21B.4040502@zytor.com> (raw)
In-Reply-To: <20140321213753.GK3132@tassilo.jf.intel.com>
On 03/21/2014 02:37 PM, Andi Kleen wrote:
> On Fri, Mar 21, 2014 at 01:46:04PM -0700, H. Peter Anvin wrote:
>> Not really. That is equally braindamaged. The problem is that KVM is telling the host that our is something it simply cannot be.
>
> Well it has to pick something. It's unlikely it will ever implement 100% of that particular CPU.
> 0 is the best you can get in many cases.
>
> Also I thought Xen did return 0.
>
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.
However, labeling it a bug in Linux is silly.
-hpa
next prev parent reply other threads:[~2014-03-21 21:42 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-21 17:42 GPF in intel_pmu_lbr_reset() with qemu -cpu host Peter Wu
2014-03-21 17:46 ` Peter Wu
2014-03-21 19:04 ` Venkatesh Srinivas
2014-03-21 19:09 ` H. Peter Anvin
2014-03-22 7:54 ` Paolo Bonzini
2014-03-22 8:50 ` Gleb Natapov
2014-03-22 10:05 ` Peter Wu
2014-03-22 12:27 ` Gleb Natapov
2014-03-22 21:46 ` H. Peter Anvin
2014-03-22 22:00 ` Peter Wu
2014-03-26 7:23 ` Wu, Feng
2014-03-26 9:38 ` Paolo Bonzini
2014-03-21 19:29 ` Andi Kleen
2014-03-21 20:46 ` H. Peter Anvin
2014-03-21 21:37 ` Andi Kleen
2014-03-21 21:41 ` H. Peter Anvin [this message]
2014-03-21 21:48 ` Andi Kleen
2014-03-21 21:55 ` H. Peter Anvin
2014-03-22 0:22 ` Andi Kleen
2014-03-22 0:26 ` H. Peter Anvin
2014-03-22 0:30 ` Andi Kleen
2014-03-22 0:34 ` H. Peter Anvin
2014-03-22 10:01 ` Borislav Petkov
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