From: Stefan Bader <stefan.bader@canonical.com>
To: Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org
Cc: Anthoine Bourgeois <bourgeois@bertin.fr>
Subject: Re: nVMX regression v3.13+, bisected
Date: Wed, 26 Feb 2014 21:27:17 +0100 [thread overview]
Message-ID: <530E4E25.4050508@canonical.com> (raw)
In-Reply-To: <530E4DB9.5050001@redhat.com>
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On 26.02.2014 21:25, Paolo Bonzini wrote:
> Il 26/02/2014 20:43, Stefan Bader ha scritto:
>> Hi,
>>
>> I was looking at a bug report[1] about a regression on nested VMX that started
>> with kernel v3.13 (same issue still existed with v3.14-rc4). The problem shows
>> up when running a v3.13 kernel in L0 and then trying to launch a L2 (L1 was
>> either a v3.2 kernel or v3.13, so seemed to have no immediate influence). L2 is
>> trying to boot a iso image and hangs before the isolinux boot loader displays
>> anything. A preinstalled hd image fails to boot, too.
>>
>> I bisected this and ended up on the following commit which, when reverted made
>> the launch work again:
>>
>> Author: Anthoine Bourgeois <bourgeois@bertin.fr>
>> Date: Wed Nov 13 11:45:37 2013 +0100
>>
>> kvm, vmx: Fix lazy FPU on nested guest
>>
>> If a nested guest does a NM fault but its CR0 doesn't contain the TS
>> flag (because it was already cleared by the guest with L1 aid) then we
>> have to activate FPU ourselves in L0 and then continue to L2. If TS flag
>> is set then we fallback on the previous behavior, forward the fault to
>> L1 if it asked for.
>>
>> Signed-off-by: Anthoine Bourgeois <bourgeois@bertin.fr>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>>
>> The condition to exit to L0 seems to be according to what the description says.
>> Could it be that the handling in L0 is doing something wrong?
>
> Thanks, I'll look at it tomorrow or Friday.
>
> Paolo
>
Great thanks. And maybe it helps if I actually add the link to the bug report as
I had intended... :-P
[1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1278531
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next prev parent reply other threads:[~2014-02-26 20:27 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-26 19:43 nVMX regression v3.13+, bisected Stefan Bader
2014-02-26 20:25 ` Paolo Bonzini
2014-02-26 20:27 ` Stefan Bader [this message]
2014-02-26 20:44 ` Kashyap Chamarthy
2014-02-27 12:10 ` Kashyap Chamarthy
2014-02-27 15:55 ` Kashyap Chamarthy
2014-02-27 10:51 ` Paolo Bonzini
2014-02-27 13:41 ` anthoine.bourgeois
2014-02-27 17:01 ` anthoine.bourgeois
2014-02-27 16:58 ` Paolo Bonzini
2014-02-27 21:34 ` Kashyap Chamarthy
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