Re: Unable to boot guest on kernel 2.6.29.1 with kvm-84 or kvm-85

Kenni Lund
2009-05-01T22:52:11Z

Avi Kivity avi@redhat.com wrote:
> Kenni Lund wrote:
> > Ok, but as I write in my message, I'm using the
> KVM modules from the latest> upstream kernel, not the kvm-85
> modules.>
> > According to the KVM download page, http://www.linux-kvm.org/page/Downloads,> any kernel above 2.6.25 should work with the
> latest KVM userspace. This has> been true until now in my case, but it breaks
> with 2.6.29.1 and that's the reason> why I'm posting this bug report.
> >
> >
>
> Can you try a bisect?

Yes, sorry for the late reply. I did the bisect as requested and it returned the following results:

# bad: [8d7bff2d72660d9d60aa371ae3d1356bbf329a09] Linux 2.6.29.1
# good: [4a6908a3a050aacc9c3a2f36b276b46c0629ad91] Linux 2.6.28
git bisect start 'v2.6.29.1' 'v2.6.28' '--' 'arch/x86/kvm' 'virt/kvm'
# good: [b82091824ee4970adf92d5cd6d57b12273171625] KVM: Prevent trace call into unloaded module text
git bisect good b82091824ee4970adf92d5cd6d57b12273171625
# good: [7f59f492da722eb3551bbe1f8f4450a21896f05d] KVM: use cpumask_var_t for cpus_hardware_enabled
git bisect good 7f59f492da722eb3551bbe1f8f4450a21896f05d
# good: [19de40a8472fa64693eab844911eec277d489f6c] KVM: change KVM to use IOMMU API
git bisect good 19de40a8472fa64693eab844911eec277d489f6c
# good: [2aaf69dcee864f4fb6402638dd2f263324ac839f] KVM: MMU: Map device MMIO as UC in EPT
git bisect good 2aaf69dcee864f4fb6402638dd2f263324ac839f
# good: [682edb4c01e690c7c7cd772dbd6f4e0fd74dc572] KVM: Fix assigned devices circular locking dependency
git bisect good 682edb4c01e690c7c7cd772dbd6f4e0fd74dc572
# bad: [f438349efb8247cd0c1d453a4131b1f801bf5691] KVM: VMX: Don't allow uninhibited access to EFER on i386
git bisect bad f438349efb8247cd0c1d453a4131b1f801bf5691
# good: [516a1a7e9dc80358030fe01aabb3bedf882db9e2] KVM: VMX: Flush volatile msrs before emulating rdmsr
git bisect good 516a1a7e9dc80358030fe01aabb3bedf882db9e2

----------------
And the final output:

f438349efb8247cd0c1d453a4131b1f801bf5691 is first bad commit
commit f438349efb8247cd0c1d453a4131b1f801bf5691
Author: Avi Kivity
Date: Thu Mar 26 23:05:03 2009 +0000

KVM: VMX: Don't allow uninhibited access to EFER on i386

upstream commit: 16175a796d061833aacfbd9672235f2d2725df65

vmx_set_msr() does not allow i386 guests to touch EFER, but they can still
do so through the default: label in the switch. If they set EFER_LME, they
can oops the host.

Fix by having EFER access through the normal channel (which will check for
EFER_LME) even on i386.

Reported-and-tested-by: Benjamin Gilbert
Cc: stable@kernel.org
Signed-off-by: Avi Kivity
Signed-off-by: Chris Wright

:040000 040000 cf7848d35c136beee6665e67839080d450977af0 0a39980481dd346306b2ac54dbe916741515f1f1 M arch

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FYI, I also tested 2.6.29.2 and the issue still exists.

Do you need more information?

Best Regards
Kenni Lund