lkml.org 
[lkml]   [2022]   [May]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v2 08/12] KVM: SVM: Update AVIC settings when changing APIC mode
From
Date
On Tue, 2022-05-03 at 20:04 +0700, Suravee Suthikulpanit wrote:
> Maxim,
>
> On 5/3/22 12:13 AM, Maxim Levitsky wrote:
> > > In the kvm/queue branch, I found a regression on nested SVM guest, where L2 guest cannot
> > > launch. The bad commit is:
> > >
> > > commit a4cfff3f0f8c07f1f7873a82bdeb3995807dac8c (bisect)
> > > Merge: 42dcbe7d8bac 8d5678a76689
> > > Author: Paolo Bonzini<pbonzini@redhat.com>
> > > Date: Fri Apr 8 12:43:40 2022 -0400
> > >
> > > Merge branch 'kvm-older-features' into HEAD
> > >
> > > Merge branch for features that did not make it into 5.18:
> > >
> > > * New ioctls to get/set TSC frequency for a whole VM
> > >
> > > * Allow userspace to opt out of hypercall patching
> > >
> > > Nested virtualization improvements for AMD:
> > >
> > > * Support for "nested nested" optimizations (nested vVMLOAD/VMSAVE,
> > > nested vGIF)
> > >
> > > * Allow AVIC to co-exist with a nested guest running
> > >
> > > * Fixes for LBR virtualizations when a nested guest is running,
> > > and nested LBR virtualization support
> > >
> > > * PAUSE filtering for nested hypervisors
> > >
> > > Guest support:
> > >
> > > * Decoupling of vcpu_is_preempted from PV spinlocks
> > >
> > > Signed-off-by: Paolo Bonzini<pbonzini@redhat.com>
> > >
> > > I am still working on the bisect into the merge commits.
> > >
> > > Regards,
> > > Suravee
> > >
> > What happens when the guest can't launch? It sure works for me for kvm/queue
> > from yesterday.
> >
> > I'll test again tomorrow.
>
> I have bisected it to this commit:
>
> commit 74fd41ed16fd71725e69e2cb90b755505326c2e6
> Author: Maxim Levitsky <mlevitsk@redhat.com>
> Date: Tue Mar 22 19:40:47 2022 +0200
>
> KVM: x86: nSVM: support PAUSE filtering when L0 doesn't intercept PAUSE
>
> Expose the pause filtering and threshold in the guest CPUID
> and support PAUSE filtering when possible:
>
> - If the L0 doesn't intercept PAUSE (cpu_pm=on), then allow L1 to
> have full control over PAUSE filtering.
>
> - if the L1 doesn't intercept PAUSE, use host values and update
> the adaptive count/threshold even when running nested.
>
> - Otherwise always exit to L1; it is not really possible to merge
> the fields correctly. It is expected that in this case, userspace
> will not enable this feature in the guest CPUID, to avoid having the
> guest update both fields pointlessly.
>
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> Message-Id: <20220322174050.241850-4-mlevitsk@redhat.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>
> I can revert this one or specify pause_filter_count=0 pause_filter_thresh=0,
> and then I can boot the L2 guest.
>
> Regards,
> Suravee
>

This is really wierd.

Could you share the qemu command line for L1 and L2 guest, and as much as possible
info on what happens when you boot L2? I tested latest kvm/queue and I don't see
any issues with booting nested guest.

Which hardware you test on? I test on Zen2 (3970X) mostly.

How many vCPUs L2 has? Could you do a kvm trace of the L2, from L1,
to see what it does prior to hang?


Best regards,
Maxim Levitsky



\
 
 \ /
  Last update: 2022-05-04 13:47    [W:0.058 / U:0.340 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site