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

[Auger Eric <eric.auger@redhat.com>]

Hi Peter,

On 25/04/2017 12:43, Peter Maydell wrote:
> On 14 April 2017 at 11:15, Eric Auger <eric.auger@redhat.com> wrote:
>> Add description for how to save GICV3 LPI pending bit into
>> guest RAM pending tables.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>
>> ---
>> v5: creation
>> ---
>>  Documentation/virtual/kvm/devices/arm-vgic-v3.txt | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/Documentation/virtual/kvm/devices/arm-vgic-v3.txt b/Documentation/virtual/kvm/devices/arm-vgic-v3.txt
>> index c1a2461..9293b45 100644
>> --- a/Documentation/virtual/kvm/devices/arm-vgic-v3.txt
>> +++ b/Documentation/virtual/kvm/devices/arm-vgic-v3.txt
>> @@ -167,11 +167,17 @@ Groups:
>>      KVM_DEV_ARM_VGIC_CTRL_INIT
>>        request the initialization of the VGIC, no additional parameter in
>>        kvm_device_attr.addr.
>> +    KVM_DEV_ARM_VGIC_SAVE_PENDING_TABLES
>> +      save all LPI pending bits into guest RAM pending tables.
>> +
>> +      The first kB of the pending table is not altered by this operation.
>>    Errors:
>>      -ENXIO: VGIC not properly configured as required prior to calling
>>       this attribute
>>      -ENODEV: no online VCPU
>>      -ENOMEM: memory shortage when allocating vgic internal data
>> +    -EFAULT: Invalid guest ram access
>> +    -EBUSY:  One or more VCPUS are running
>>
>>
>>    KVM_DEV_ARM_VGIC_GRP_LEVEL_INFO
>> --
>> 2.5.5
> 
> 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().

Thanks

Eric
> 
> thanks
> -- PMM
> 
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