linux-kernel - Re: [PATCH 0/4] KVM: selftests: Introduce VM_MODE_PXXV48

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Date:   Thu, 29 Aug 2019 09:32:53 +0800
From:   Peter Xu <peterx@...hat.com>
To:     Andrew Jones <drjones@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Huth <thuth@...hat.com>
Subject: Re: [PATCH 0/4] KVM: selftests: Introduce VM_MODE_PXXV48_4K

On Wed, Aug 28, 2019 at 01:52:30PM +0200, Andrew Jones wrote:
> On Wed, Aug 28, 2019 at 01:51:06PM +0200, Andrew Jones wrote:
> > On Tue, Aug 27, 2019 at 09:10:11PM +0800, Peter Xu wrote:
> > > The work is based on Thomas's s390 port for dirty_log_test.

[1]

> > > 
> > > This series originates from "[PATCH] KVM: selftests: Detect max PA
> > > width from cpuid" [1] and one of Drew's comments - instead of keeping
> > > the hackish line to overwrite guest_pa_bits all the time, this series
> > > introduced the new mode VM_MODE_PXXV48_4K for x86_64 platform.
> > > 
> > > The major issue is that even all the x86_64 kvm selftests are
> > > currently using the guest mode VM_MODE_P52V48_4K, many x86_64 hosts
> > > are not using 52 bits PA (and in most cases, far less).  If with luck
> > > we could be having 48 bits hosts, but it's more adhoc (I've observed 3
> > > x86_64 systems, they are having different PA width of 36, 39, 48).  I
> > > am not sure whether this is happening to the other archs as well, but
> > > it probably makes sense to bring the x86_64 tests to the real world on
> > > always using the correct PA bits.
> > > 
> > > A side effect of this series is that it will also fix the crash we've
> > > encountered on Xeon E3-1220 as mentioned [1] due to the
> > > differenciation of PA width.
> > > 
> > > With [1], we've observed AMD host issues when with NPT=off.  However a
> > > funny fact is that after I reworked into this series, the tests can
> > > instead pass on both NPT=on/off.  It could be that the series changes
> > > vm->pa_bits or other fields so something was affected.  I didn't dig
> > > more on that though, considering we should not lose anything.
> > > 
> > > Any kind of smoke test would be greatly welcomed (especially on s390
> > > or ARM).  Same to comments.  Thanks,
> > > 
> > 
> > The patches didn't apply cleanly for me on 9e8312f5e160, but once I got
> > them applied I was able to run the aarch64 tests.

Right, because I applied Thomas's s390x port as base [1], considering
that that one should reach kvm/queue earlier (should be in the
submaintainer's tree and waiting for a pull).  Maybe I should post
against the current kvm/queue next time?  After all this series does
not modify anything of the s390x work so the conflict should be
trivial.

> 
> Oh, and after fixing 2/4 (vm->pa_bits) to fix compilation on aarch64 as
> pointed out on that patch.

Thanks for verifying and reviews!  Yes I'll fix that up.

Regards,

-- 
Peter Xu