[PATCH 1/5] KVM: arm64: Correctly honor the presence of FEAT_TCRX

Marc Zyngier
2024-06-25T13:00:49Z

We currently blindly enable TCR2_EL1 use in a guest, irrespective
of the feature set. This is obviously wrong, and we should actually
honor the guest configuration and handle the possible trap resulting
from the guest being buggy.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/include/asm/kvm_arm.h | 2 +-
arch/arm64/kvm/sys_regs.c | 9 +++++++++
2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index b2adc2c6c82a5..e6682a3ace5af 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -102,7 +102,7 @@
#define HCR_HOST_NVHE_PROTECTED_FLAGS (HCR_HOST_NVHE_FLAGS | HCR_TSC)
#define HCR_HOST_VHE_FLAGS (HCR_RW | HCR_TGE | HCR_E2H)

-#define HCRX_GUEST_FLAGS (HCRX_EL2_SMPME | HCRX_EL2_TCR2En)
+#define HCRX_GUEST_FLAGS (HCRX_EL2_SMPME)
#define HCRX_HOST_FLAGS (HCRX_EL2_MSCEn | HCRX_EL2_TCR2En | HCRX_EL2_EnFPM)

/* TCR_EL2 Registers bits */
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 22b45a15d0688..71996d36f3751 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -383,6 +383,12 @@ static bool access_vm_reg(struct kvm_vcpu *vcpu,
bool was_enabled = vcpu_has_cache_enabled(vcpu);
u64 val, mask, shift;

+ if (reg_to_encoding(r) == SYS_TCR2_EL1 &&
+ !kvm_has_feat(vcpu->kvm, ID_AA64MMFR3_EL1, TCRX, IMP)) {
+ kvm_inject_undefined(vcpu);
+ return false;
+ }
+
BUG_ON(!p->is_write);

get_access_mask(r, &mask, &shift);
@@ -4060,6 +4066,9 @@ void kvm_init_sysreg(struct kvm_vcpu *vcpu)

if (kvm_has_feat(kvm, ID_AA64ISAR2_EL1, MOPS, IMP))
vcpu->arch.hcrx_el2 |= (HCRX_EL2_MSCEn | HCRX_EL2_MCE2);
+
+ if (kvm_has_feat(kvm, ID_AA64MMFR3_EL1, TCRX, IMP))
+ vcpu->arch.hcrx_el2 |= HCRX_EL2_TCR2En;
}

if (test_bit(KVM_ARCH_FLAG_FGU_INITIALIZED, &kvm->arch.flags))
--
2.39.2