From: Alexander Graf <agraf@csgraf.de>
To: Frank Yang <lfy@google.com>
Cc: Peter Maydell <peter.maydell@linaro.org>,
Eduardo Habkost <ehabkost@redhat.com>,
Richard Henderson <richard.henderson@linaro.org>,
qemu-devel <qemu-devel@nongnu.org>,
Cameron Esfahani <dirty@apple.com>,
Roman Bolshakov <r.bolshakov@yadro.com>,
qemu-arm <qemu-arm@nongnu.org>,
Claudio Fontana <cfontana@suse.de>,
Paolo Bonzini <pbonzini@redhat.com>,
Peter Collingbourne <pcc@google.com>
Subject: Re: [PATCH v1 1/1] hvf: arm: Properly sync guest time on migration
Date: Wed, 2 Dec 2020 23:28:27 +0100 [thread overview]
Message-ID: <2dc974cc-abe2-d034-1720-d5a2651a9042@csgraf.de> (raw)
In-Reply-To: <CAEkmjvXGccGs2QhaiLFupTDWcnp4O+qez-uj8QdbRG13UfCy2Q@mail.gmail.com>
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On 02.12.20 23:19, Frank Yang wrote:
>
> From downstream:
> https://android-review.googlesource.com/c/platform/external/qemu/+/1515002
> <https://android-review.googlesource.com/c/platform/external/qemu/+/1515002>
>
> Based on v3 of Alexander Graf's patches
>
> https://patchew.org/QEMU/20201202190408.2041-1-agraf@csgraf.de
> <https://patchew.org/QEMU/20201202190408.2041-1-agraf@csgraf.de>
>
> We need to adjust CNTVOFF_EL2 so that time doesnt warp. Even though we
> can set separate CNTVOFF_EL2 values per vCPU, it just is not worth the
> require effort to do that accurately---with individual values, even if
> they are a tiny bit off it can result in a lockup due to inconsistent
> time differences between vCPUs. So just use a global approximate value
> for now.
>
> Not tested in upstream yet, but Android emulator snapshots work without
> time warp now.
>
> Signed-off-by: Lingfeng Yang <lfy@google.com <mailto:lfy@google.com>>
If we just always make CNTV start at the same 0 as QEMU_CLOCK_VIRTUAL,
we should be able to just recover the offset after migration by looking
at QEMU_CLOCK_VIRTUAL to set CNTVOFF, right?
That would end up much easier than this patch I hope.
Alex
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next prev parent reply other threads:[~2020-12-02 22:29 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-02 22:19 [PATCH v1 1/1] hvf: arm: Properly sync guest time on migration Frank Yang
2020-12-02 22:22 ` Frank Yang
2020-12-02 22:28 ` Alexander Graf [this message]
2020-12-02 22:46 ` Frank Yang
2020-12-02 22:56 ` Alexander Graf
2020-12-02 23:25 ` Frank Yang
2020-12-02 23:39 ` Peter Collingbourne
2020-12-03 10:26 ` Alexander Graf
2020-12-02 23:28 ` Peter Collingbourne
2020-12-03 10:29 ` Alexander Graf
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