From f414269392443f666bd8bef0cb3f0b53d5147be3 Mon Sep 17 00:00:00 2001 From: Per Larsen Date: Wed, 20 Aug 2025 01:10:05 +0000 Subject: [PATCH] KVM: arm64: Correct return value on host version downgrade attempt Once the hypervisor negotiates the FF-A version with the host, it should remain locked-in. However, it is possible to load FF-A as a module first supporting version 1.1 and then 1.0. Without this patch, the FF-A 1.0 driver will use 1.0 data structures to make calls which the hypervisor will incorrectly interpret as 1.1 data structures. With this patch, negotiation will fail. This patch does not change existing functionality in the case where a FF-A 1.2 driver is loaded after a 1.1 driver; the 1.2 driver will need to use 1.1 in order to proceed. Acked-by: Will Deacon Signed-off-by: Per Larsen Signed-off-by: Marc Zyngier --- arch/arm64/kvm/hyp/nvhe/ffa.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c index 3369dd0c4009f..2c199d40811ef 100644 --- a/arch/arm64/kvm/hyp/nvhe/ffa.c +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c @@ -712,7 +712,10 @@ 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; } -- 2.47.3