KVM: arm64: at: Update AF on software walk only if VM has FEAT_HAFDBS

A guest can write 1 to TCR_ELx.HA, making the KVM software walker update
the access flag in a table descriptor even if FEAT_HAFDBS is not present.
Avoid this by making wi->ha depend on FEAT_HAFDBS being enabled in the VM,
similar to how the software walker treats FEAT_HPDS.

This is not needed for VTCR_EL2.HA, since a guest will always write to
the in-memory copy of the register, where the HA bit is masked (set to
0) by KVM if the VM doesn't have FEAT_HAFDBS.

Fixes: c59ca4b5b0c3 ("KVM: arm64: Implement HW access flag management in stage-1 SW PTW")
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Link: https://msgid.link/20251128100946.74210-5-alexandru.elisei@arm.com
Signed-off-by: Oliver Upton <oupton@kernel.org>

diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
index 6d41a95f6c60efbf7486d0ee3097ce383aa097a6..53bf70126f81dda8eb1e06f6228e3be7f3794d13 100644 (file)
--- a/arch/arm64/kvm/at.c
+++ b/arch/arm64/kvm/at.c
@@ -346,7 +346,8 @@ static int setup_s1_walk(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
 
        wi->baddr &= GENMASK_ULL(wi->max_oa_bits - 1, x);
 
-       wi->ha = (wi->regime == TR_EL2 ?
+       wi->ha  = kvm_has_feat(vcpu->kvm, ID_AA64MMFR1_EL1, HAFDBS, AF);
+       wi->ha &= (wi->regime == TR_EL2 ?
                  FIELD_GET(TCR_EL2_HA, tcr) :
                  FIELD_GET(TCR_HA, tcr));