FROMLIST: KVM: arm64: Restrict FF-A host version renegotiation
Prevent the host from re-negotiating a lesser minor version with the
hypervisor. Once the hypervisor negotiates a version, that should
remain locked in. Fix the current behaviour by returning NOT_SUPPORTED
to avoid the FF-A interoperability rules with lesser minor versions that
allow the host version to downgrade.
Bug: 269285339
Link: https://lore.kernel.org/all/20250516-virtio-msg-ffa-v4-1-580ee70e5081@google.com
Change-Id: I18e26a1a467f89ce421f31f577b3f15c37dfcf1a
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Per Larsen <perlarsen@google.com>
diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index a8fa431..93c82a8 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -1367,7 +1367,10 @@ static void do_ffa_version(struct arm_smccc_res *res,
hyp_spin_lock(&version_lock);
if (has_version_negotiated) {
- res->a0 = hyp_ffa_version;
+ if (FFA_MINOR_VERSION(ffa_req_version) < FFA_MINOR_VERSION(hyp_ffa_version))
+ res->a0 = FFA_RET_NOT_SUPPORTED;
+ else
+ res->a0 = hyp_ffa_version;
goto unlock;
}
