[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] Help debugging a regression in KVM Module
From: |
Peter Lieven |
Subject: |
Re: [Qemu-devel] Help debugging a regression in KVM Module |
Date: |
Tue, 18 Aug 2015 17:37:02 +0200 |
> Am 18.08.2015 um 17:25 schrieb Radim Krčmář <address@hidden>:
>
> 2015-08-18 16:54+0200, Peter Lieven:
>> After some experiments I was able to find out the bad commit that introduced
>> the regression:
>>
>> commit f30ebc312ca9def25650b4e1d01cdb425c310dca
>> Author: Radim Krčmář <address@hidden>
>> Date: Thu Oct 30 15:06:47 2014 +0100
>>
>> It seems that this optimisation is not working reliabliy after live
>> migration. I can't reproduce if
>> I take a 3.19 kernel and revert this single commit.
>
> Hello, this bug has gone unnoticed for a long time so it is fixed only
> since v4.1 (and v3.19.stable was dead at that point).
thanks for the pointer. i noticed the regression some time ago, but never found
the time to debug. some distros rely on 3.19 e.g. Ubuntu LTS 14.04.2. I will
try to ping the maintainer.
Peter
>
> commit b6ac069532218027f2991cba01d7a72a200688b0
> Author: Radim Krčmář <address@hidden>
> Date: Fri Jun 5 20:57:41 2015 +0200
>
> KVM: x86: fix lapic.timer_mode on restore
>
> lapic.timer_mode was not properly initialized after migration, which
> broke few useful things, like login, by making every sleep eternal.
>
> Fix this by calling apic_update_lvtt in kvm_apic_post_state_restore.
>
> There are other slowpaths that update lvtt, so this patch makes sure
> something similar doesn't happen again by calling apic_update_lvtt
> after every modification.
>
> Cc: address@hidden
> Fixes: f30ebc312ca9 ("KVM: x86: optimize some accesses to LVTT and SPIV")
> Signed-off-by: Radim Krčmář <address@hidden>
> Signed-off-by: Marcelo Tosatti <address@hidden>