From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To: Eduardo Habkost <ehabkost@redhat.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>,
qemu-devel <qemu-devel@nongnu.org>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: 5.1.0-rc1 regression: reset fails with kvm and -cpu host
Date: Thu, 23 Jul 2020 09:40:26 +0100 [thread overview]
Message-ID: <20200723084026.GB2622@work-vm> (raw)
In-Reply-To: <20200722212159.GQ1274972@habkost.net>
* Eduardo Habkost (ehabkost@redhat.com) wrote:
> On Wed, Jul 22, 2020 at 04:47:32PM -0400, Eduardo Habkost wrote:
> > On Wed, Jul 22, 2020 at 08:05:01PM +0200, Jan Kiszka wrote:
> > > On 22.07.20 19:35, Eduardo Habkost wrote:
> > > > Hi Jan,
> > > >
> > > > What was the last version where it worked for you? Does using
> > > > "-cpu host,-vmx" help?
> > >
> > > Yeah, -vmx does indeed help.
> > >
> > > I didn't have the time to bisect yet. Just check my reflog, picked
> > > eb6490f544, and that works.
> >
> > Thanks!
> >
> > I could reproduce it locally[1], I will bisect it.
> >
> > The good news is that "-cpu host,+vmx" still works, on commit
> > eb6490f544.
> >
> > [1] Linux 5.6.19-300.fc32.x86_64, Intel Core i7-8665U CPU.
>
> Bisected to:
>
> commit b16c0e20c74218f2d69710cedad11da7dd4d2190
> Author: Paolo Bonzini <pbonzini@redhat.com>
> Date: Wed May 20 10:49:22 2020 -0400
>
> KVM: add support for AMD nested live migration
>
> Support for nested guest live migration is part of Linux 5.8, add the
> corresponding code to QEMU. The migration format consists of a few
> flags, is an opaque 4k blob.
>
> The blob is in VMCB format (the control area represents the L1 VMCB
> control fields, the save area represents the pre-vmentry state; KVM does
> not use the host save area since the AMD manual allows that) but QEMU
> does not really care about that. However, the flags need to be
> copied to hflags/hflags2 and back.
>
> In addition, support for retrieving and setting the AMD nested virtualization
> states allows the L1 guest to be reset while running a nested guest, but
> a small bug in CPU reset needs to be fixed for that to work.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Guesswork led me to try reverting the chunk in kvm_put_nested_state;
without it the reset seems to work; I can't explain that code though.
Dave
>
> --
> Eduardo
>
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
next prev parent reply other threads:[~2020-07-23 8:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-22 9:15 5.1.0-rc1 regression: reset fails with kvm and -cpu host Jan Kiszka
2020-07-22 17:35 ` Eduardo Habkost
2020-07-22 18:05 ` Jan Kiszka
2020-07-22 20:47 ` Eduardo Habkost
2020-07-22 21:21 ` Eduardo Habkost
2020-07-23 8:40 ` Dr. David Alan Gilbert [this message]
2020-07-23 10:21 ` Philippe Mathieu-Daudé
2020-07-23 12:21 ` Vitaly Kuznetsov
2020-07-23 12:52 ` Dr. David Alan Gilbert
2020-07-23 13:01 ` Jan Kiszka
2020-07-23 13:26 ` Vitaly Kuznetsov
2020-07-23 13:35 ` Paolo Bonzini
2020-07-23 13:47 ` Vitaly Kuznetsov
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