[PATCH 4/4] KVM: arm64: Derive GUEST_HAS_SVE from the SVE feature bit at EL2

[Fuad Tabba <fuad.tabba@linux.dev>]

pkvm_init_features_from_host() takes KVM_ARCH_FLAG_GUEST_HAS_SVE and
KVM_ARM_VCPU_SVE from the host separately, but pkvm_vcpu_init_sve()
tests the bit while vcpu_has_sve() reads the flag. A host that sets the
flag without the bit gets a vCPU with a NULL sve_state that the world
switch loads the guest's SVE state from.

Derive the flag from the bit, and drop the protected path's copy of the
host's flag, which is dead code since protected VMs are not allowed SVE.

Fixes: 41d6028e28bd ("KVM: arm64: Convert the SVE guest vcpu flag to a vm flag")
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
 arch/arm64/kvm/hyp/nvhe/pkvm.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c
index 1d8cc984fb88c..6efca70e5f5a9 100644
--- a/arch/arm64/kvm/hyp/nvhe/pkvm.c
+++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c
@@ -360,7 +360,7 @@ static void pkvm_init_features_from_host(struct pkvm_hyp_vm *hyp_vm, const struc
 		if (test_bit(KVM_ARCH_FLAG_WRITABLE_IMP_ID_REGS, &host_arch_flags))
 			hyp_vm->kvm.arch.midr_el1 = host_kvm->arch.midr_el1;
 
-		return;
+		goto out;
 	}
 
 	if (kvm_pkvm_ext_allowed(kvm, KVM_CAP_ARM_MTE))
@@ -379,13 +379,14 @@ static void pkvm_init_features_from_host(struct pkvm_hyp_vm *hyp_vm, const struc
 	if (kvm_pkvm_ext_allowed(kvm, KVM_CAP_ARM_PTRAUTH_GENERIC))
 		set_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, allowed_features);
 
-	if (kvm_pkvm_ext_allowed(kvm, KVM_CAP_ARM_SVE)) {
+	if (kvm_pkvm_ext_allowed(kvm, KVM_CAP_ARM_SVE))
 		set_bit(KVM_ARM_VCPU_SVE, allowed_features);
-		kvm->arch.flags |= host_arch_flags & BIT(KVM_ARCH_FLAG_GUEST_HAS_SVE);
-	}
 
 	bitmap_and(kvm->arch.vcpu_features, host_kvm->arch.vcpu_features,
 		   allowed_features, KVM_VCPU_MAX_FEATURES);
+out:
+	__assign_bit(KVM_ARCH_FLAG_GUEST_HAS_SVE, &kvm->arch.flags,
+		     kvm_vcpu_has_feature(kvm, KVM_ARM_VCPU_SVE));
 }
 
 static void unpin_host_vcpu(struct kvm_vcpu *host_vcpu)
-- 
2.39.5