From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: xen-devel@lists.xensource.com, Jed Smith <jed@linode.com>,
Jan Beulich <JBeulich@novell.com>,
Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Subject: Re: Re: [PATCH] x86: unconditionally mark TSC unstable under Xen
Date: Thu, 15 Jul 2010 09:45:03 -0700 [thread overview]
Message-ID: <4C3F3B0F.1040107@goop.org> (raw)
In-Reply-To: <b97b2105-e814-471e-b87f-0e2bc5bcbec6@default>
On 07/15/2010 09:40 AM, Dan Magenheimer wrote:
> Isn't the real problem that, in a PV guest, the cpuid instructions
> that are testing the TSC-related CPUID bits are obtaining the actual
> hardware value, rather than what Xen would like the guest to believe?
>
No, because there shouldn't be any "naked" rdtscs in the kernel.
> IOW, isn't the correct fix to use pvcpuid instead of cpuid when
> xen_pvdomain() is true?
>
Every use of cpuid in the kernel goes via the cpuid pvop, which ends up
doing the Xen cpuid rather than the native one. Usermode cpuid is still
the "real" one, unless they explicitly use the Xen version.
J
next prev parent reply other threads:[~2010-07-15 16:45 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-14 19:24 [PATCH] x86: unconditionally mark TSC unstable under Xen Jed Smith
2010-07-14 21:36 ` Jeremy Fitzhardinge
[not found] ` <alpine.DEB.2.00.1007151656380.21432@kaball-desktop 4C3F37A5.9050606@goop.org>
2010-07-14 22:29 ` Jed Smith
2010-07-15 14:23 ` Jed Smith
2010-07-15 15:57 ` Stefano Stabellini
2010-07-15 16:30 ` Jeremy Fitzhardinge
2010-07-15 16:40 ` Dan Magenheimer
2010-07-15 16:45 ` Jeremy Fitzhardinge [this message]
2010-07-15 17:14 ` Dan Magenheimer
2010-07-15 17:30 ` Jeremy Fitzhardinge
2010-07-15 17:48 ` Dan Magenheimer
2010-07-15 18:05 ` Jeremy Fitzhardinge
2010-08-15 20:57 ` Ævar Arnfjörð Bjarmason
2010-08-15 23:40 ` Jeremy Fitzhardinge
2010-08-16 1:27 ` Ævar Arnfjörð Bjarmason
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