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

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Message-ID: <20190828115106.2j6n7qust7uceds5@kamzik.brq.redhat.com>
Date:   Wed, 28 Aug 2019 13:51:06 +0200
From:   Andrew Jones <drjones@...hat.com>
To:     Peter Xu <peterx@...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 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.
> 
> 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.

> [1] https://lkml.org/lkml/2019/8/26/141
> 
> Peter Xu (4):
>   KVM: selftests: Move vm type into _vm_create() internally
>   KVM: selftests: Create VM earlier for dirty log test
>   KVM: selftests: Introduce VM_MODE_PXXV48_4K
>   KVM: selftests: Remove duplicate guest mode handling
> 
>  tools/testing/selftests/kvm/dirty_log_test.c  | 78 +++++--------------
>  .../testing/selftests/kvm/include/kvm_util.h  | 17 +++-
>  .../selftests/kvm/lib/aarch64/processor.c     |  3 +
>  tools/testing/selftests/kvm/lib/kvm_util.c    | 77 ++++++++++++++----
>  .../selftests/kvm/lib/x86_64/processor.c      |  8 +-
>  5 files changed, 107 insertions(+), 76 deletions(-)
> 
> -- 
> 2.21.0
>

Thanks,
drew