[PATCH 5.10 113/151] KVM: arm64: Make ICC_*SGI*_EL1 undef in the absence of a vGICv3

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5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marc Zyngier <maz@xxxxxxxxxx>

commit 3e6245ebe7ef341639e9a7e402b3ade8ad45a19f upstream.

On a system with a GICv3, if a guest hasn't been configured with
GICv3 and that the host is not capable of GICv2 emulation,
a write to any of the ICC_*SGI*_EL1 registers is trapped to EL2.

We therefore try to emulate the SGI access, only to hit a NULL
pointer as no private interrupt is allocated (no GIC, remember?).

The obvious fix is to give the guest what it deserves, in the
shape of a UNDEF exception.

Reported-by: Alexander Potapenko <glider@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20240820100349.3544850-2-maz@xxxxxxxxxx
Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/arm64/kvm/sys_regs.c  |    6 ++++++
 arch/arm64/kvm/vgic/vgic.h |    7 +++++++
 2 files changed, 13 insertions(+)

--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -30,6 +30,7 @@
 #include <trace/events/kvm.h>
 
 #include "sys_regs.h"
+#include "vgic/vgic.h"
 
 #include "trace.h"
 
@@ -275,6 +276,11 @@ static bool access_gic_sgi(struct kvm_vc
 {
 	bool g1;
 
+	if (!kvm_has_gicv3(vcpu->kvm)) {
+		kvm_inject_undefined(vcpu);
+		return false;
+	}
+
 	if (!p->is_write)
 		return read_from_write_only(vcpu, p, r);
 
--- a/arch/arm64/kvm/vgic/vgic.h
+++ b/arch/arm64/kvm/vgic/vgic.h
@@ -318,4 +318,11 @@ int vgic_v4_init(struct kvm *kvm);
 void vgic_v4_teardown(struct kvm *kvm);
 void vgic_v4_configure_vsgis(struct kvm *kvm);
 
+static inline bool kvm_has_gicv3(struct kvm *kvm)
+{
+	return (static_branch_unlikely(&kvm_vgic_global_state.gicv3_cpuif) &&
+		irqchip_in_kernel(kvm) &&
+		kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3);
+}
+
 #endif






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