Re: [RFC PATCH 20/45] KVM: arm/arm64: vgic-new: Add TARGET registers handlers

Christoffer Dall
2016-04-12T13:16:58Z

On Mon, Apr 11, 2016 at 01:10:24PM +0100, Andre Przywara wrote:
> On 31/03/16 12:31, Christoffer Dall wrote:
> > On Fri, Mar 25, 2016 at 02:04:43AM +0000, Andre Przywara wrote:
> >> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> >> ---
> >> virt/kvm/arm/vgic/vgic_mmio.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
> >> 1 file changed, 42 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/virt/kvm/arm/vgic/vgic_mmio.c b/virt/kvm/arm/vgic/vgic_mmio.c
> >> index 76657ce..cde153f 100644
> >> --- a/virt/kvm/arm/vgic/vgic_mmio.c
> >> +++ b/virt/kvm/arm/vgic/vgic_mmio.c
> >> @@ -471,6 +471,47 @@ static int vgic_mmio_write_config(struct kvm_vcpu *vcpu,
> >> return 0;
> >> }
> >>
> >> +static int vgic_mmio_read_target(struct kvm_vcpu *vcpu,
> >> + struct kvm_io_device *this,
> >> + gpa_t addr, int len, void *val)
> >> +{
> >> + struct vgic_io_device *iodev = container_of(this,
> >> + struct vgic_io_device, dev);
> >> + u32 intid = (addr - iodev->base_addr);
> >> + int i;
> >> +
> >> + if (iodev->redist_vcpu)
> >> + vcpu = iodev->redist_vcpu;
> >> +
> >> + for (i = 0; i < len; i++) {
> >> + struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
> >> +
> >> + ((u8 *)val)[i] = irq->targets;
> >> + }
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +static int vgic_mmio_write_target(struct kvm_vcpu *vcpu,
> >> + struct kvm_io_device *this,
> >> + gpa_t addr, int len, const void *val)
> >> +{
> >> + struct vgic_io_device *iodev = container_of(this,
> >> + struct vgic_io_device, dev);
> >> + u32 intid = (addr - iodev->base_addr);
> >> + int i;
> >> +
> >> + /* GICD_ITARGETSR[0-7] are read-only */
> >> + if (intid < VGIC_NR_PRIVATE_IRQS)
> >> + return 0;
> >> +
> >> + for (i = 0; i < len; i++)
> >> + vgic_v2_irq_change_affinity(vcpu->kvm, intid + i,
> >> + ((u8 *)val)[i]);
> >> +
> >> + return 0;
> >> +}
> >> +
> >
> > these functions are v2 specific but are in a generic file and are not
> > named anything specific to v2?
>
> Well, technically the target register is still defined for the GICv3
> distributor, but just RES0 if affinity routing is enabled.

Shouldn't we support that then (or do we do this already via a call to
a RAZ handle function in the register table instead)?

> But I can of course easily add a _v2_ in here.
>
> While I look at the function, it makes me wonder if the abstraction for
> the affinity change call is actually correct at all. In contrast to the
> other vgic_v<n>_* functions this one is about the _emulated_ VGIC model,
> not the hardware GIC version.
> Also we actually only have this one user here, the other call is about
> initializing the affinity setting, for which this function is really
> overkill.

How is it overkill? In that it takes locks which are not necessary?

> So what about we move the content of the change_affinity function in
> here (same for the v3 case later), and tackle the init case separately
> (which is trivial)?

I don't think there's much to gain in moving the code into the function,
on the contrary, but you could move the function into this file and make
it static.

So, you're saying that the current _vX_ functions we have denote the
hardware version, not the emulated version, so that would be wrong to do
here?

In that case, I think we should just add a comment at the top of this
function saying it deals with GICv2 stuff only. That, or forget I ever
said anything here.

Thanks,
-Christoffer

>
> >
> >> struct vgic_register_region vgic_v2_dist_registers[] = {
> >> REGISTER_DESC_WITH_LENGTH(GIC_DIST_CTRL,
> >> vgic_mmio_read_v2_misc, vgic_mmio_write_v2_misc, 12),
> >> @@ -491,7 +532,7 @@ struct vgic_register_region vgic_v2_dist_registers[] = {
> >> REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_PRI,
> >> vgic_mmio_read_priority, vgic_mmio_write_priority, 8),
> >> REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_TARGET,
> >> - vgic_mmio_read_nyi, vgic_mmio_write_nyi, 8),
> >> + vgic_mmio_read_target, vgic_mmio_write_target, 8),
> >> REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_CONFIG,
> >> vgic_mmio_read_config, vgic_mmio_write_config, 2),
> >> REGISTER_DESC_WITH_LENGTH(GIC_DIST_SOFTINT,
> >> --
> >> 2.7.3
> >>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe kvm" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at http://vger.kernel.org/majordomo-info.html
> >