Bug#838660: linux/jessie: missing KVM fix causes migration issues on guests without rdtscp
Source: linux
Version: 3.16.36-1+deb8u1
Severity: normal
Tags: patch
User: debian-admin@lists.debian.org
Usertags: needed-by-DSA-Team
Dear Maintainer,
The following fix went to kernel 3.16.7-ckt25-1, as it was Cc:ed to
stable@vger.kernel.org:
| commit 9dbe6cf941a6fe82933aef565e4095fb10f65023
| Author: Paolo Bonzini <pbonzini@redhat.com>
| Date: Thu Nov 12 14:49:17 2015 +0100
|
| KVM: x86: expose MSR_TSC_AUX to userspace
|
| If we do not do this, it is not properly saved and restored across
| migration. Windows notices due to its self-protection mechanisms,
| and is very upset about it (blue screen of death).
|
| Cc: Radim Krcmar <rkrcmar@redhat.com>
| Cc: stable@vger.kernel.org
| Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
However it has been followed a bit later by the following fix, which has
not been Cc:ed to stable@vger.kernel.org and thus not backported:
| commit 81b1b9ca6d5ca5f3ce91c0095402def657cf5db3
| Author: Haozhong Zhang <haozhong.zhang@intel.com>
| Date: Mon Dec 14 23:13:38 2015 +0800
|
| KVM: VMX: Fix host initiated access to guest MSR_TSC_AUX
|
| The current handling of accesses to guest MSR_TSC_AUX returns error if
| vcpu does not support rdtscp, though those accesses are initiated by
| host. This can result in the reboot failure of some versions of
| QEMU. This patch fixes this issue by passing those host initiated
| accesses for further handling instead.
|
| Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
| Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This causes guest migrations issues when the host supports the rdtscp
instruction, but it is not exposed to the guest. The migration itself
works fine, but then the guest is frozen on the target host.
This patch does not apply cleanly to the 3.16 kernel, but can be
backported relatively easily. It has already been backported in
v4.2.8-ckt5 already, so the patch can be taken from there directly.
Thanks,
Aurelien
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