Commit ebbcaece authored by Fuad Tabba's avatar Fuad Tabba Committed by Marc Zyngier
Browse files

KVM: arm64: Fix MTE flag initialization for protected VMs 



The function pkvm_init_features_from_host() initializes guest
features, propagating them from the host. The logic to propagate
KVM_ARCH_FLAG_MTE_ENABLED (Memory Tagging Extension)
has a couple of issues.

First, the check was in the common path, before the divergence for
protected and non-protected VMs. For non-protected VMs, this was
unnecessary, as 'kvm->arch.flags' is completely overwritten by
host_arch_flags immediately after, which already contains the MTE flag.
For protected VMs, this was setting the flag even if the feature is not
allowed.

Second, the check was reading 'host_kvm->arch.flags' instead of using
the local 'host_arch_flags', which is read once from the host flags.

Fix these by moving the MTE flag check inside the protected-VM-only
path, checking if the feature is allowed, and changing it to use the
correct host_arch_flags local variable. This ensures non-protected VMs
get the flag via the bulk copy, and protected VMs get it via an explicit
check.

Fixes: b7f345fb ("KVM: arm64: Fix FEAT_MTE in pKVM")
Reviewed-by: default avatarBen Horgan <ben.horgan@arm.com>
Signed-off-by: default avatarFuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20251211104710.151771-4-tabba@google.com


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent e913c7ce

arch/arm64/kvm/hyp/nvhe/pkvm.c

+3 −3
Original line number Diff line number Diff line
@@ -340,9 +340,6 @@ static void pkvm_init_features_from_host(struct pkvm_hyp_vm *hyp_vm, const struc 
	/* Preserve the vgic model so that GICv3 emulation works */

	hyp_vm->kvm.arch.vgic.vgic_model = host_kvm->arch.vgic.vgic_model;



	if (test_bit(KVM_ARCH_FLAG_MTE_ENABLED, &host_kvm->arch.flags))

		set_bit(KVM_ARCH_FLAG_MTE_ENABLED, &kvm->arch.flags);



	/* No restrictions for non-protected VMs. */

	if (!kvm_vm_is_protected(kvm)) {

		hyp_vm->kvm.arch.flags = host_arch_flags;
@@ -357,6 +354,9 @@ static void pkvm_init_features_from_host(struct pkvm_hyp_vm *hyp_vm, const struc 
		return;

	}



	if (kvm_pvm_ext_allowed(KVM_CAP_ARM_MTE))

		kvm->arch.flags |= host_arch_flags & BIT(KVM_ARCH_FLAG_MTE_ENABLED);



	bitmap_zero(allowed_features, KVM_VCPU_MAX_FEATURES);



	set_bit(KVM_ARM_VCPU_PSCI_0_2, allowed_features);