Hi,

On 12/05/16 19:41, Christoffer Dall wrote:

On Fri, May 06, 2016 at 11:45:58AM +0100, Andre Przywara wrote:

quoted

Userland may want to save and restore the state of the in-kernel VGIC,
so we provide the code which takes a userland request and translate
that into calls to our MMIO framework.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
 virt/kvm/arm/vgic/vgic-kvm-device.c | 50 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/arm/vgic/vgic-kvm-device.c b/virt/kvm/arm/vgic/vgic-kvm-device.c
index c952f6f..bb33af8 100644
--- a/virt/kvm/arm/vgic/vgic-kvm-device.c
+++ b/virt/kvm/arm/vgic/vgic-kvm-device.c

@@ -264,7 +264,55 @@ static int vgic_attr_regs_access(struct kvm_device *dev,

come to think of it, this is GICv2 specific right?

why don't we call it vgic_v2_attr_regs_access then?

and should it really live in this file?

Mmmh, at the moment every userland access is v2 specific, but
potentially this function should cover GICv3 as well, I think. We might
need some adjustments once this will be implemented, but in general I
don't see anything too v2 specific in here?

quoted

 				 struct kvm_device_attr *attr,
 				 u32 *reg, bool is_write)
 {
-	return -ENXIO;
+	gpa_t addr;
+	int cpuid, ret, c;
+	struct kvm_vcpu *vcpu, *tmp_vcpu;
+
+	cpuid = (attr->attr & KVM_DEV_ARM_VGIC_CPUID_MASK) >>
+		 KVM_DEV_ARM_VGIC_CPUID_SHIFT;
+	vcpu = kvm_get_vcpu(dev->kvm, cpuid);
+	addr = attr->attr & KVM_DEV_ARM_VGIC_OFFSET_MASK;
+
+	mutex_lock(&dev->kvm->lock);
+
+	ret = vgic_init(dev->kvm);
+	if (ret)
+		goto out;
+
+	if (cpuid >= atomic_read(&dev->kvm->online_vcpus)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/*
+	 * Ensure that no other VCPU is running by checking the vcpu->cpu
+	 * field.  If no other VPCUs are running we can safely access the VGIC
+	 * state, because even if another VPU is run after this point, that
+	 * VCPU will not touch the vgic state, because it will block on
+	 * getting the vgic->lock in kvm_vgic_sync_hwstate().
+	 */

eh, I don't see us grabbing any vgic->lock (does that still exist?)
here?

Yeah, that scared me the other day too.
In fact I think we cannot guarantee this requirement anymore with our
existing locks - but maybe we can pause the guest explicitly as we do
now for the clear-active handler?

Cheers,
Andre.

quoted

+	kvm_for_each_vcpu(c, tmp_vcpu, dev->kvm) {
+		if (unlikely(tmp_vcpu->cpu != -1)) {
+			ret = -EBUSY;
+			goto out;
+		}
+	}
+
+	switch (attr->group) {
+	case KVM_DEV_ARM_VGIC_GRP_CPU_REGS:
+		ret = -EINVAL;
+		break;
+	case KVM_DEV_ARM_VGIC_GRP_DIST_REGS:
+		ret = vgic_v2_dist_uaccess(vcpu, is_write, addr, reg);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+out:
+	mutex_unlock(&dev->kvm->lock);
+	return ret;
 }
 
 /* V2 ops */
-- 
2.7.3

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Thanks,
-Christoffer