[PATCH v4 0/3] irqfd support for arm/arm64

Andre Przywara andre.przywara at arm.com
Mon Nov 24 10:10:13 PST 2014


On 24/11/14 10:10, Eric Auger wrote:
> On 11/24/2014 10:47 AM, Christoffer Dall wrote:
>> On Sun, Nov 23, 2014 at 06:56:57PM +0100, Eric Auger wrote:
>>> This patch series enables irqfd on arm and arm64.
>>> Irqfd framework enables to inject a virtual IRQ into a guest upon an
>>> eventfd trigger. User-side uses KVM_IRQFD VM ioctl to provide KVM with
>>> a kvm_irqfd struct that associates a VM, an eventfd, a virtual IRQ number
>>> (aka. the gsi). When an actor signals the eventfd (typically a VFIO
>>> platform driver), the kvm irqfd subsystem injects the gsi into the VM.
>>> Resamplefd also is supported for level sensitive interrupts, ie. the
>>> user can provide another eventfd that is triggered when the completion
>>> of the virtual IRQ (gsi) is detected by the GIC.
>>> The gsi must correspond to a shared peripheral interrupt (SPI), ie the
>>> GIC interrupt ID is gsi + 32.
>>> The rationale behind not supporting PPI irqfd injection is that
>>> any device using a PPI would be a private-to-the-CPU device (timer for
>>> instance), so its state would have to be context-switched along with the
>>> VCPU and would require in-kernel wiring anyhow. It is not a relevant use
>>> case for irqfds.
>>> No IRQ routing table is used, enabling to remove CONFIG_HAVE_KVM_IRQCHIP
>>> can be found at git://git.linaro.org/people/eric.auger/linux.git
>>> on branch irqfd_integ_v8
>>> This work was tested with Calxeda Midway xgmac main interrupt with
>>> qemu-system-arm and QEMU VFIO platform device. Also irqfd was proven
>>> functional on several vhost-net prototypes.
>>> v3 -> v4:
>>> - rebase on 3.18rc5
>>> - vgic dynamic instantiation brought new challenges:
>>>   handling of irqfd injection when vgic is not ready
>>> - unset of CONFIG_HAVE_KVM_IRQCHIP in a separate patch
>>> - add arm64 enable
>>> - vgic.c style modifications according to Christoffer comments
>> There also seems to be a different split of the patches here?
> Hi Christoffer,
> yes I added arm64b support and moved CONFIG_HAVE_KVM_IRQCHIP removal in
> a separate patch.
>> We've probably also reached the point where you need to start rebasing
>> on Andre's GICv3 patches, which I expect will go in first.
> the patch applies without conflict on Andre's series.

Yes, I can confirm this. I also manually checked the patches to spot any
fallouts due to the vgic.c file split, but Eric's patches are not
affected by this.


> BR
> Eric
>> Thanks,
>> -Christoffer
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