[PATCH 2/3] KVM: arm64: Copy MIDR_EL1 into hyp VM when it is writable

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

KVM recently added a capability that allows userspace to override the
'implementation ID' registers presented to the VM. MIDR_EL1 is a special
example, where the hypervisor can directly set the value when read from
EL1 using VPIDR_EL2.

Copy the VM-wide value for MIDR_EL1 into the hyp VM for non-protected
guests when the capability is enabled so VPIDR_EL2 gets set up
correctly.

Reported-by: Mark Brown <broonie@kernel.org>
Closes: https://lore.kernel.org/kvmarm/ac594b9c-4bbb-46c8-9391-e7a68ce4de5b@sirena.org.uk/
Fixes: 3adaee783061 ("KVM: arm64: Allow userspace to change the implementation ID registers")
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
 arch/arm64/kvm/hyp/nvhe/pkvm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c
index 2e2975248cd3..afc1b5c403c9 100644
--- a/arch/arm64/kvm/hyp/nvhe/pkvm.c
+++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c
@@ -376,6 +376,9 @@ static void init_pkvm_hyp_vm(struct kvm *host_kvm, struct pkvm_hyp_vm *hyp_vm,
 	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;
+
+	if (test_bit(KVM_ARCH_FLAG_WRITABLE_IMP_ID_REGS, &hyp_vm->kvm.arch.flags))
+		hyp_vm->kvm.arch.midr_el1 = host_kvm->arch.midr_el1;
 }
 
 static void pkvm_vcpu_init_sve(struct pkvm_hyp_vcpu *hyp_vcpu, struct kvm_vcpu *host_vcpu)
-- 
2.39.5