KVM: arm64: Move GICv5 timer PPI validation into timer_irqs_are_valid()

Userspace can set the timer PPI numbers way before a GIC has been
created, leading to odd behaviours on GICv5 as we'd accept non
architectural PPI numbers.

Move the v5 check into timer_irqs_are_valid(), which aligns the
behaviour with the pre-v5 GICs, and is also guaranteed to run
only once a GIC has been configured.

Reviewed-by: Sascha Bischoff <sascha.bischoff@arm.com>
Fixes: 9491c63b6cd7b ("KVM: arm64: gic-v5: Enlighten arch timer for GICv5")
Link: https://sashiko.dev/#/patchset/20260319154937.3619520-1-sascha.bischoff%40arm.com
Link: https://patch.msgid.link/20260401103611.357092-14-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>

diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
index 6608c47d1f6282ddb20cf2ddf66e8399d259e185..cbea4d9ee95522f8d0946b15f84754a54f225c4d 100644 (file)
--- a/arch/arm64/kvm/arch_timer.c
+++ b/arch/arm64/kvm/arch_timer.c
@@ -1543,6 +1543,10 @@ static bool timer_irqs_are_valid(struct kvm_vcpu *vcpu)
                if (kvm_vgic_set_owner(vcpu, irq, ctx))
                        break;
 
+               /* With GICv5, the default PPI is what you get -- nothing else */
+               if (vgic_is_v5(vcpu->kvm) && irq != get_vgic_ppi(vcpu->kvm, default_ppi[i]))
+                       break;
+
                /*
                 * We know by construction that we only have PPIs, so all values
                 * are less than 32 for non-GICv5 VGICs. On GICv5, they are
@@ -1678,13 +1682,6 @@ int kvm_arm_timer_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
                return -ENXIO;
        }
 
-       /*
-        * The PPIs for the Arch Timers are architecturally defined for
-        * GICv5. Reject anything that changes them from the specified value.
-        */
-       if (vgic_is_v5(vcpu->kvm) && vcpu->kvm->arch.timer_data.ppi[idx] != irq)
-               return -EINVAL;
-
        /*
         * We cannot validate the IRQ unicity before we run, so take it at
         * face value. The verdict will be given on first vcpu run, for each