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From:   David Matlack <dmatlack@google.com>
Date:   Tue, 14 Mar 2023 09:00:28 -0700
Message-ID: <CALzav=c-wtJiz9M6hpPtcoBMFvFP5_2BNYoY66NzF-J+8_W6NA@mail.gmail.com>
Subject: Re: [PATCH V5 0/2] selftests: KVM: Add a test for eager page splitting
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Ben Gardon <bgardon@google.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, Peter Xu <peterx@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Vipin Sharma <vipinsh@google.com>,
        Ricardo Koller <ricarkol@google.com>
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On Tue, Mar 14, 2023 at 7:23=E2=80=AFAM Paolo Bonzini <pbonzini@redhat.com>=
 wrote:
>
> On Tue, Mar 14, 2023 at 2:27=E2=80=AFPM Paolo Bonzini <pbonzini@redhat.co=
m> wrote:
> > I have finally queued it, but made a small change to allow running it
> > with non-hugetlbfs page types.
>
> Oops, it fails on my AMD workstation:
>
> $ tools/testing/selftests/kvm/x86_64/dirty_log_page_splitting_test
> Testing guest mode: PA-bits:ANY, VA-bits:48,  4K pages
> guest physical test memory: [0x7fc7fe00000, 0x7fcffe00000)
> =3D=3D=3D=3D Test Assertion Failure =3D=3D=3D=3D
>   x86_64/dirty_log_page_splitting_test.c:195: __a =3D=3D __b
>   pid=3D1378203 tid=3D1378203 errno=3D0 - Success
>      1    0x0000000000402d02: run_test at dirty_log_page_splitting_test.c=
:195
>      2    0x000000000040367c: for_each_guest_mode at guest_modes.c:100
>      3    0x00000000004024df: main at dirty_log_page_splitting_test.c:245
>      4    0x00007f4227c3feaf: ?? ??:0
>      5    0x00007f4227c3ff5f: ?? ??:0
>      6    0x0000000000402594: _start at ??:?
>   ASSERT_EQ(stats_populated.pages_4k, stats_repopulated.pages_4k) failed.
>     stats_populated.pages_4k is 0x413
>     stats_repopulated.pages_4k is 0x412
>
> Haven't debugged it yet.

I wonder if pages are getting swapped, especially if running on a
workstation. If so, mlock()ing all guest memory VMAs might be
necessary to be able to assert exact page counts.

>
> Paolo
>