Re: [RFC 9/9] KVM: KVM_VFIO: ARM: implement irq forwarding control

Eric Auger
2014-08-27T15:24:53Z

On 08/26/2014 09:02 PM, Alex Williamson wrote:
> On Mon, 2014-08-25 at 15:27 +0200, Eric Auger wrote:
>> Implements ARM specific KVM-VFIO device group commands:
>> - KVM_DEV_VFIO_DEVICE_ASSIGN_IRQ
>> - KVM_DEV_VFIO_DEVICE_DEASSIGN_IRQ
>> capability can be queried using KVM_HAS_DEVICE_ATTR.
>>
>> The new commands enable to set IRQ forwarding on/off for a given
>> IRQ index of a VFIO platform device.
>>
>> as soon as a forwarded irq is set, a reference to the VFIO device
>> is taken by the kvm-vfio device.
>>
>> The kvm-vfio device stores in the kvm_vfio_arch_data the list
>> of "assigned" devices (kvm_vfio_device). Each kvm_vfio_device
>> stores the list of assigned IRQs (potentially allowed a subset of
>> IRQ to be forwarded)
>>
>> The kvm-vfio device programs both the GIC and vGIC. Also it
>> clears the active bit on destruction, in case the guest did not
>> do it itself.
>>
>> Changing the forwarded state is not allowed in the critical
>> section starting from VFIO IRQ handler to LR programming. It is
>> up to the client to take care of this.
>>
>> Signed-off-by: Eric Auger <eric.auger@linaro.org>
>> ---
>> arch/arm/include/asm/kvm_host.h | 2 +
>> arch/arm/kvm/Makefile | 2 +-
>> arch/arm/kvm/kvm_vfio_arm.c | 599 ++++++++++++++++++++++++++++++++++++++++
>> 3 files changed, 602 insertions(+), 1 deletion(-)
>> create mode 100644 arch/arm/kvm/kvm_vfio_arm.c
>
> I'm really happy that it seems like the kvm-vfio device is going to work
> for you, but I think too much stuff is being pushed out to arch code
> here. Exporting the interfaces in patches 7 & 8 are setting the stage
> for duplicate code for anyone wanting to implement device attributes.
> Instead, I think the core code should support the list of
> kvm_vfio_devices with proper cleanup, and we should attempt to access
> the kvm_vfio_ callbacks as little as possible from arch code. Thanks,

OK. my next iteration will feature much more generic code.

Thanks for the review

Best Regards

Eric

>
> Alex
>