From: Juergen Gross <jgross@suse.com>
To: "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, tglx@linutronix.de, mingo@redhat.com,
linux-kernel@vger.kernel.org, akataria@vmware.com,
jongman.heo@samsung.com
Subject: Re: [PATCH] x86: don't rely on VMWare emulating PAT MSR correctly
Date: Wed, 17 Dec 2014 05:52:59 +0100 [thread overview]
Message-ID: <54910C2B.3000805@suse.com> (raw)
In-Reply-To: <54906212.2010102@zytor.com>
On 12/16/2014 05:47 PM, H. Peter Anvin wrote:
> On 12/16/2014 01:58 AM, Juergen Gross wrote:
>> VMWare seems not to emulate the PAT MSR correctly: reaeding
>> MSR_IA32_CR_PAT returns 0 even after writing another value to it.
>>
>> Detect this bug and don't use the read value if it is 0.
>>
>> Commit bd809af16e3ab1f8d55b3e2928c47c67e2a865d2 ("x86: Enable PAT to
>> use cache mode translation tables") triggers this VMWare bug when the
>> kernel is booted as a VMWare guest.
>>
>> Reported-by: Jongman Heo <jongman.heo@samsung.com>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> Tested-by: Jongman Heo <jongman.heo@samsung.com>
>
> I presume cachability control is irrelevant for a VMware guest? I'm
> wondering if it would be better to just plain ignore the failure rather
> than disabling PAT.
I'd rather disable PAT as this seems to be like a PAT erratum.
In case you want to keep PAT active I can redo the patch to not rely on
the read MSR value in the non-Xen case (under Xen reading the MSR is the
only way to obtain the correct settings).
Juergen
next prev parent reply other threads:[~2014-12-17 4:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-16 9:58 [PATCH] x86: don't rely on VMWare emulating PAT MSR correctly Juergen Gross
2014-12-16 16:47 ` H. Peter Anvin
2014-12-17 4:52 ` Juergen Gross [this message]
2014-12-17 4:57 ` Alok Kataria
2015-01-07 4:58 ` Juergen Gross
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