Re: [PATCH v5 02/22] KVM: arm/arm64: Add GICV3 pending table save API documentation

Auger Eric
2017-04-26T09:57:23Z

Hi Peter, Dave,

On 26/04/2017 10:48, Dr. David Alan Gilbert wrote:
> * Peter Maydell (peter.maydell@linaro.org) wrote:
>> On 26 April 2017 at 09:26, Auger Eric <eric.auger@redhat.com> wrote:
>>> On 25/04/2017 12:43, Peter Maydell wrote:
>>>> When does the -EFAULT return happen? (if the guest points GITS_BASER<n>
>>>> etc at invalid memory, presumably?)
>>>
>>> Yes that's correct, when GICR_PENDBASER contains a bad GPA.
>>>
>>>> How does the QEMU migration code
>>>> handle this case? Failing migration because the guest has done something
>>>> silly doesn't seem too palatable, but trying to avoid that could be
>>>> more effort than an obscure corner case really merits.
>>>
>>> The kvm_device_access will cause an abort() as for other errors returned
>>> by kvm_device_ioctl().
>>
>> That's pretty nasty. Guests shouldn't be able to provoke QEMU
>> into abort()ing, ideally. We don't necessarily have to produce
>> a successful migration, but we should at least fail it cleanly.
>
> Yes, no abort()'s during migration due to guest behaviour.
> They always end up coming back around to being filed as migration
> bugs and people worry why they've got cores.
>
> Ideally log a message into stderr to say that the guest state
> is inconsistent so that when someone comes to debug it then they
> can see it's obvious.

OK I agree. I will respin the QEMU part accordingly and in that
situation I won't abort and will print a message.

Thanks

Eric
>
> Dave
>
>> thanks
>> -- PMM
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
>
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