From 039f49c4cafb785504c678f28664d088e0108d35 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Sat, 28 May 2022 12:38:12 +0100 Subject: KVM: arm64: Always start with clearing SME flag on load On each vcpu load, we set the KVM_ARM64_HOST_SME_ENABLED flag if SME is enabled for EL0 on the host. This is used to restore the correct state on vpcu put. However, it appears that nothing ever clears this flag. Once set, it will stick until the vcpu is destroyed, which has the potential to spuriously enable SME for userspace. As it turns out, this is due to the SME code being more or less copied from SVE, and inheriting the same shortcomings. We never saw the issue because nothing uses SME, and the amount of testing is probably still pretty low. Fixes: 861262ab8627 ("KVM: arm64: Handle SME host state when running guests") Signed-off-by: Marc Zyngier Reviwed-by: Mark Brown Link: https://lore.kernel.org/r/20220528113829.1043361-3-maz@kernel.org --- arch/arm64/kvm/fpsimd.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c index 8267ff4642d3..6012b08ecb14 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -94,6 +94,7 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) * operations. Do this for ZA as well for now for simplicity. */ if (system_supports_sme()) { + vcpu->arch.flags &= ~KVM_ARM64_HOST_SME_ENABLED; if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN) vcpu->arch.flags |= KVM_ARM64_HOST_SME_ENABLED; -- cgit v1.2.3