From: Marc Zyngier Date: Wed, 1 Apr 2026 10:36:03 +0000 (+0100) Subject: KVM: arm64: vgic-v5: Cast vgic_apr to u32 to avoid undefined behaviours X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=42d7eac8291d2724b3897141ab2f226c69b7923e;p=thirdparty%2Fkernel%2Flinux.git KVM: arm64: vgic-v5: Cast vgic_apr to u32 to avoid undefined behaviours Passing a u64 to __builtin_ctz() is odd, and requires some digging to figure out why this construct is indeed safe as long as the HW is correct. But it is much easier to make it clear to the compiler by casting the u64 into an intermediate u32, and be done with the UD. Reviewed-by: Sascha Bischoff Fixes: 933e5288fa971 ("KVM: arm64: gic-v5: Check for pending PPIs") Link: https://sashiko.dev/#/patchset/20260319154937.3619520-1-sascha.bischoff%40arm.com Link: https://patch.msgid.link/20260401103611.357092-9-maz@kernel.org Signed-off-by: Marc Zyngier --- diff --git a/arch/arm64/kvm/vgic/vgic-v5.c b/arch/arm64/kvm/vgic/vgic-v5.c index 422741c86c6a..0f269321ece4 100644 --- a/arch/arm64/kvm/vgic/vgic-v5.c +++ b/arch/arm64/kvm/vgic/vgic-v5.c @@ -212,7 +212,7 @@ int vgic_v5_finalize_ppi_state(struct kvm *kvm) static u32 vgic_v5_get_effective_priority_mask(struct kvm_vcpu *vcpu) { struct vgic_v5_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v5; - u32 highest_ap, priority_mask; + u32 highest_ap, priority_mask, apr; /* * If the guest's CPU has not opted to receive interrupts, then the @@ -227,7 +227,8 @@ static u32 vgic_v5_get_effective_priority_mask(struct kvm_vcpu *vcpu) * priority. Explicitly use the 32-bit version here as we have 32 * priorities. 32 then means that there are no active priorities. */ - highest_ap = cpu_if->vgic_apr ? __builtin_ctz(cpu_if->vgic_apr) : 32; + apr = cpu_if->vgic_apr; + highest_ap = apr ? __builtin_ctz(apr) : 32; /* * An interrupt is of sufficient priority if it is equal to or