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From: "Jan Beulich" <JBeulich@suse.com>
To: Sheng Yang <sheng@yasker.org>
Cc: jeremy@goop.org, keir@xen.org, xen-devel@lists.xen.org
Subject: Re: Debian stable kernel got timer issue when running as PV guest
Date: Fri, 13 Apr 2012 08:56:27 +0100	[thread overview]
Message-ID: <4F87F84B020000780007DB52@nat28.tlf.novell.com> (raw)
In-Reply-To: <CA+2rt42-KhN7G_P6hKuqc5n3mc8ZKer1Pgr5HT1GXOf440tRYA@mail.gmail.com>

>>> On 12.04.12 at 21:22, Sheng Yang <sheng@yasker.org> wrote:
> I've compiled a kernel, force sched_clock_stable=0, then it solved the
> timestamp jump issue as expected. Luckily, seems it also solved the call
> trace and guest hang issue as well.

And this is also how it should be fixed.

> Attachment is a (untested) patch to mask the CPUID leaf 0x80000007. I think
> the issue can be easily reproduced using a Westmere or SandyBridge
> machine(my old colleagues at Intel said the feature likely existed after
> Nehalem) running newer version of PV guest, check the guest cpuinfo you
> would see nonstop_tsc, and you would notice the abnormal timestamp of
> printk.

Masking the entire leaf is certainly out of question. And even masking
the individual bit is questionable - a PV kernel simply shouldn't look at
it imo (for other than possibly reporting to user mode purposes).

Jan

  reply	other threads:[~2012-04-13  7:56 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CA+2rt42Z+8Bg9wh=LPphQKBOV6Rxgpm7D8LdKOOq7_X6GVOKxw@mail.gmail.com>
2012-04-12 19:22 ` Debian stable kernel got timer issue when running as PV guest Sheng Yang
2012-04-13  7:56   ` Jan Beulich [this message]
2012-04-13 10:37     ` David Vrabel
2012-04-13 11:00       ` Jan Beulich
2012-04-13 16:10         ` David Vrabel
2012-04-13 16:15           ` Sheng Yang
2012-04-13 17:27     ` Sheng Yang

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