From: Alexander Graf <graf@amazon.com>
To: Andre Przywara <andre.przywara@arm.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>,
kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Subject: Re: [PATCH kvm-unit-tests] arm: Add PL031 test
Date: Thu, 11 Jul 2019 11:59:07 +0200 [thread overview]
Message-ID: <e1ea413e-a809-2a42-3888-204d7c037ab3@amazon.com> (raw)
In-Reply-To: <20190711104200.254073fb@donnerap.cambridge.arm.com>
On 11.07.19 11:42, Andre Przywara wrote:
> On Thu, 11 Jul 2019 09:52:42 +0200
> Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> Hi,
>
>> On 11/07/19 07:49, Alexander Graf wrote:
>>>> I agree that it would belong more in qtest, but tests in not exactly the
>>>> right place is better than no tests.
>>>
>>> The problem with qtest is that it tests QEMU device models from a QEMU
>>> internal view.
>>
>> Not really: fundamentally it tests QEMU device models with stimuli that
>> come from another process in the host, rather than code that runs in a
>> guest. It does have hooks into QEMU's internal view (mostly to
>> intercept interrupts and advance the clocks), but the main feature of
>> the protocol is the ability to do memory reads and writes.
>>
>>> I am much more interested in the guest visible side of things. If
>>> kvmtool wanted to implement a PL031, it should be able to execute the
>>> same test that we run against QEMU, no?
>
> One of the design goals of kvmtool is to get away with as little emulation
> as possible, in favour of paravirtualisation (so it's just virtio and not
> IDE/flash). So a hardware RTC emulation sounds dispensable in this context.
The main reason to have a PL031 exposed to a VM is to make OVMF happy,
so that it can provide wall clock time runtime services. I suppose that
sooner or later you may want to run OVMF in kvmtool as well, no?
The alternative to the PL031 here is to do a PV interface, yes. I'm not
really convinced that that would be any easier though. The PL031 is a
very trivial device. The only real downside is that it will wrap around
in 2038.
Alex
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next prev parent reply other threads:[~2019-07-11 10:07 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-10 13:27 [PATCH kvm-unit-tests] arm: Add PL031 test Alexander Graf
2019-07-10 14:25 ` Marc Zyngier
2019-07-12 8:29 ` Alexander Graf
2019-07-12 8:51 ` Marc Zyngier
2019-07-10 14:37 ` Alexandru Elisei
2019-07-10 17:02 ` Andre Przywara
2019-07-10 17:06 ` Paolo Bonzini
2019-07-11 5:49 ` Alexander Graf
2019-07-11 7:52 ` Paolo Bonzini
2019-07-11 9:42 ` Andre Przywara
2019-07-11 9:52 ` Marc Zyngier
2019-07-11 9:59 ` Alexander Graf [this message]
2019-07-11 8:51 ` Peter Maydell
2019-07-11 9:11 ` Alexander Graf
2019-07-11 9:13 ` Peter Maydell
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