From: Andrew Jones <drjones@redhat.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: bijan.mottahedeh@oracle.com, Marc Zyngier <maz@kernel.org>,
Richard Henderson <richard.henderson@linaro.org>,
QEMU Developers <qemu-devel@nongnu.org>,
qemu-arm <qemu-arm@nongnu.org>, Heyi Guo <guoheyi@huawei.com>,
msys.mizuma@gmail.com
Subject: Re: [RFC PATCH v2 5/5] target/arm/cpu: Add the kvm-no-adjvtime CPU property
Date: Mon, 20 Jan 2020 11:31:04 +0100 [thread overview]
Message-ID: <20200120103104.quc4r6577c6rrpux@kamzik.brq.redhat.com> (raw)
In-Reply-To: <CAFEAcA8=FcrT8dRMDzxu14J-gv5LEDuNBNpD5yo9j3waV7u8iw@mail.gmail.com>
On Mon, Dec 16, 2019 at 03:06:57PM +0000, Peter Maydell wrote:
> Incidentally, if I understand things correctly, for TCG the
> behaviour is (and has always been) that VM-stopped time is
> not counted, because we run the emulated versions of these counters
> off QEMU_CLOCK_VIRTUAL. So having the KVM default be the same as
> the TCG default is nicely consistent.
It's correct that the vtimer has always been this way for TCG.
However TCG and KVM still won't be the same with the adjvtime
patches. The reason is that TCG also bases the ptimer off
QEMU_CLOCK_VIRTUAL. This means on TCG ptimer == vtimer and
both will lag a clocksource outside the VM.
I'm not sure if TCG people want to change that to match KVM.
If so, then I guess the ptimer should be based off
QEMU_CLOCK_REALTIME.
Thanks,
drew
next prev parent reply other threads:[~2020-01-20 10:33 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-12 17:33 [RFC PATCH v2 0/5] target/arm/kvm: Adjust virtual time Andrew Jones
2019-12-12 17:33 ` [RFC PATCH v2 1/5] hw: add compat machines for 5.0 Andrew Jones
2019-12-12 18:27 ` David Hildenbrand
2019-12-12 19:24 ` Eduardo Habkost
2019-12-13 7:10 ` Andrew Jones
2019-12-13 5:00 ` David Gibson
2019-12-12 17:33 ` [RFC PATCH v2 2/5] target/arm/kvm64: kvm64 cpus have timer registers Andrew Jones
2019-12-12 17:33 ` [RFC PATCH v2 3/5] target/arm/kvm: Implement virtual time adjustment Andrew Jones
2019-12-16 15:14 ` Peter Maydell
2019-12-16 15:40 ` Peter Maydell
2019-12-16 16:43 ` Andrew Jones
2019-12-16 18:06 ` Peter Maydell
2019-12-19 14:30 ` Andrew Jones
2020-01-20 9:40 ` Andrew Jones
2019-12-16 16:36 ` Andrew Jones
2019-12-12 17:33 ` [RFC PATCH v2 4/5] tests/arm-cpu-features: Check feature default values Andrew Jones
2019-12-12 17:33 ` [RFC PATCH v2 5/5] target/arm/cpu: Add the kvm-no-adjvtime CPU property Andrew Jones
2019-12-16 15:06 ` Peter Maydell
2019-12-16 16:52 ` Andrew Jones
2019-12-16 16:57 ` Peter Maydell
2020-01-20 10:31 ` Andrew Jones [this message]
2020-02-06 12:08 ` Philippe Mathieu-Daudé
2020-02-06 12:40 ` Andrew Jones
2020-02-06 22:46 ` Philippe Mathieu-Daudé
2020-02-07 7:37 ` Andrew Jones
2019-12-16 15:33 ` [RFC PATCH v2 0/5] target/arm/kvm: Adjust virtual time Peter Maydell
2019-12-16 15:44 ` Peter Maydell
2020-01-20 13:45 ` Andrew Jones
2019-12-16 16:18 ` Marc Zyngier
2019-12-16 16:59 ` Andrew Jones
2019-12-16 17:05 ` Marc Zyngier
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