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KVM: arm64: Fix MTE flag initialization for protected VMs

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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: b7f345fbc3 ("KVM: arm64: Fix FEAT_MTE in pKVM")
Reviewed-by: Ben Horgan <ben.horgan@arm.com>
Signed-off-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20251211104710.151771-4-tabba@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Fuad Tabba 2025-12-11 10:47:03 +00:00 committed by Marc Zyngier
parent e913c7ce9e
commit ebbcaece84
1 changed files with 3 additions and 3 deletions
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6
arch/arm64/kvm/hyp/nvhe/pkvm.c
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@ -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);