From 7ae2f3db6167aa7184529fdacd1de72619baf93b Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Sat, 30 May 2020 17:22:19 +0100 Subject: [PATCH] KVM: arm64: Flush the instruction cache if not unmapping the VM on reboot On a system with FWB, we don't need to unmap Stage-2 on reboot, as even if userspace takes this opportunity to repaint the whole of memory, FWB ensures that the data side stays consistent even if the guest uses non-cacheable mappings. However, the I-side is not necessarily coherent with the D-side if CTR_EL0.DIC is 0. In this case, invalidate the i-cache to preserve coherency. Reported-by: Alexandru Elisei Reviewed-by: Alexandru Elisei Fixes: 892713e97ca1 ("KVM: arm64: Sidestep stage2_unmap_vm() on vcpu reset when S2FWB is supported") Signed-off-by: Marc Zyngier --- arch/arm64/kvm/arm.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index b0b569f2cdd0..d6988401c22a 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -989,11 +989,17 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu, * Ensure a rebooted VM will fault in RAM pages and detect if the * guest MMU is turned off and flush the caches as needed. * - * S2FWB enforces all memory accesses to RAM being cacheable, we - * ensure that the cache is always coherent. + * S2FWB enforces all memory accesses to RAM being cacheable, + * ensuring that the data side is always coherent. We still + * need to invalidate the I-cache though, as FWB does *not* + * imply CTR_EL0.DIC. */ - if (vcpu->arch.has_run_once && !cpus_have_const_cap(ARM64_HAS_STAGE2_FWB)) - stage2_unmap_vm(vcpu->kvm); + if (vcpu->arch.has_run_once) { + if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB)) + stage2_unmap_vm(vcpu->kvm); + else + __flush_icache_all(); + } vcpu_reset_hcr(vcpu);