[PATCH 01/12] KVM: arm64: Make ICC_*SGI*_EL1 undef in the absence of a vGICv3

Marc Zyngier
2024-08-20T10:06:11Z

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@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
---
arch/arm64/kvm/sys_regs.c | 6 ++++++
arch/arm64/kvm/vgic/vgic.h | 7 +++++++
2 files changed, 13 insertions(+)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index c90324060436..31e49da867ff 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -33,6 +33,7 @@
#include <trace/events/kvm.h>

#include "sys_regs.h"
+#include "vgic/vgic.h"

#include "trace.h"

@@ -435,6 +436,11 @@ static bool access_gic_sgi(struct kvm_vcpu *vcpu,
{
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);

diff --git a/arch/arm64/kvm/vgic/vgic.h b/arch/arm64/kvm/vgic/vgic.h
index ba8f790431bd..8532bfe3fed4 100644
--- a/arch/arm64/kvm/vgic/vgic.h
+++ b/arch/arm64/kvm/vgic/vgic.h
@@ -346,4 +346,11 @@ void vgic_v4_configure_vsgis(struct kvm *kvm);
void vgic_v4_get_vlpi_state(struct vgic_irq *irq, bool *val);
int vgic_v4_request_vpe_irq(struct kvm_vcpu *vcpu, int irq);

+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
--
2.39.2