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* [PATCH] KVM: arm64: gic-v3: Only set ICH_HCR traps for v2-on-v3 or v3 guests
@ 2025-10-07 16:07 Sascha Bischoff
  2025-10-13 16:56 ` Marc Zyngier
  2025-10-21  0:21 ` Mark Brown
  0 siblings, 2 replies; 9+ messages in thread
From: Sascha Bischoff @ 2025-10-07 16:07 UTC (permalink / raw)
  To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org
  Cc: nd, maz@kernel.org, oliver.upton@linux.dev, Joey Gouly,
	Suzuki Poulose, yuzenghui@huawei.com

The ICH_HCR_EL2 traps are used when running on GICv3 hardware, or when
running a GICv3-based guest using FEAT_GCIE_LEGACY on GICv5
hardware. When running a GICv2 guest on GICv3 hardware the traps are
used to ensure that the guest never sees any part of GICv3 (only GICv2
is visible to the guest), and when running a GICv3 guest they are used
to trap in specific scenarios. They are not applicable for a
GICv2-native guest, and won't be applicable for a(n upcoming) GICv5
guest.

The traps themselves are configured in the vGIC CPU IF state, which is
stored as a union. Updating the wrong aperture of the union risks
corrupting state, and therefore needs to be avoided at all costs.

Bail early if we're not running a compatible guest (GICv2 on GICv3
hardware, GICv3 native, GICv3 on GICv5 hardware). Trap everything
unconditionally if we're running a GICv2 guest on GICv3
hardware. Otherwise, conditionally set up GICv3-native trapping.

Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
---
 arch/arm64/kvm/vgic/vgic-v3.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index b9ad7c42c5b01..bc42c05b53bac 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -297,8 +297,11 @@ void vcpu_set_ich_hcr(struct kvm_vcpu *vcpu)
 {
 	struct vgic_v3_cpu_if *vgic_v3 = &vcpu->arch.vgic_cpu.vgic_v3;
 
+	if (!vgic_is_v3(vcpu->kvm))
+		return;
+
 	/* Hide GICv3 sysreg if necessary */
-	if (!kvm_has_gicv3(vcpu->kvm)) {
+	if (vcpu->kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V2) {
 		vgic_v3->vgic_hcr |= (ICH_HCR_EL2_TALL0 | ICH_HCR_EL2_TALL1 |
 				      ICH_HCR_EL2_TC);
 		return;
-- 
2.34.1


^ permalink raw reply related	[flat|nested] 9+ messages in thread
end of thread, other threads:[~2025-10-21 18:48 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-10-07 16:07 [PATCH] KVM: arm64: gic-v3: Only set ICH_HCR traps for v2-on-v3 or v3 guests Sascha Bischoff
2025-10-13 16:56 ` Marc Zyngier
2025-10-21  0:21 ` Mark Brown
2025-10-21  0:50   ` Sean Christopherson
2025-10-21 11:39     ` Mark Brown
2025-10-21  7:50   ` Marc Zyngier
2025-10-21 14:00     ` Mark Brown
2025-10-21 14:37       ` Marc Zyngier
2025-10-21 18:47         ` Mark Brown

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