[PATCH 1/3] KVM: arm64: Copy guest CTR_EL0 into hyp VM

[Oliver Upton <oliver.upton@linux.dev>]

Since commit 2843cae26644 ("KVM: arm64: Treat CTR_EL0 as a VM feature
ID register") KVM has allowed userspace to configure the VM-wide view of
CTR_EL0, falling back to trap-n-emulate if the value doesn't match
hardware. It appears that this has worked by chance in protected-mode
for some time, and on systems with FEAT_EVT protected-mode
unconditionally sets TID4 (i.e. TID2 traps sans CTR_EL0).

Forward the guest CTR_EL0 value through to the hyp VM and align the
TID2/TID4 configuration with the non-protected setup.

Fixes: 2843cae26644 ("KVM: arm64: Treat CTR_EL0 as a VM feature ID register")
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
 arch/arm64/kvm/hyp/nvhe/pkvm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c
index 3927fe52a3dd..2e2975248cd3 100644
--- a/arch/arm64/kvm/hyp/nvhe/pkvm.c
+++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c
@@ -46,7 +46,8 @@ static void pkvm_vcpu_reset_hcr(struct kvm_vcpu *vcpu)
 		vcpu->arch.hcr_el2 |= HCR_FWB;
 
 	if (cpus_have_final_cap(ARM64_HAS_EVT) &&
-	    !cpus_have_final_cap(ARM64_MISMATCHED_CACHE_TYPE))
+	    !cpus_have_final_cap(ARM64_MISMATCHED_CACHE_TYPE) &&
+	    kvm_read_vm_id_reg(vcpu->kvm, SYS_CTR_EL0) == read_cpuid(CTR_EL0))
 		vcpu->arch.hcr_el2 |= HCR_TID4;
 	else
 		vcpu->arch.hcr_el2 |= HCR_TID2;
@@ -374,6 +375,7 @@ static void init_pkvm_hyp_vm(struct kvm *host_kvm, struct pkvm_hyp_vm *hyp_vm,
 	hyp_vm->kvm.arch.pkvm.enabled = READ_ONCE(host_kvm->arch.pkvm.enabled);
 	hyp_vm->kvm.arch.flags = 0;
 	pkvm_init_features_from_host(hyp_vm, host_kvm);
+	hyp_vm->kvm.arch.ctr_el0 = host_kvm->arch.ctr_el0;
 }
 
 static void pkvm_vcpu_init_sve(struct pkvm_hyp_vcpu *hyp_vcpu, struct kvm_vcpu *host_vcpu)
-- 
2.39.5