From da2e37b55d4c65baa713215e22419f54986d088f Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Mon, 15 Mar 2021 11:10:00 +0000 Subject: KVM: arm64: Ensure I-cache isolation between vcpus of a same VM Commit 01dc9262ff5797b675c32c0c6bc682777d23de05 upstream. It recently became apparent that the ARMv8 architecture has interesting rules regarding attributes being used when fetching instructions if the MMU is off at Stage-1. In this situation, the CPU is allowed to fetch from the PoC and allocate into the I-cache (unless the memory is mapped with the XN attribute at Stage-2). If we transpose this to vcpus sharing a single physical CPU, it is possible for a vcpu running with its MMU off to influence another vcpu running with its MMU on, as the latter is expected to fetch from the PoU (and self-patching code doesn't flush below that level). In order to solve this, reuse the vcpu-private TLB invalidation code to apply the same policy to the I-cache, nuking it every time the vcpu runs on a physical CPU that ran another vcpu of the same VM in the past. This involve renaming __kvm_tlb_flush_local_vmid() to __kvm_flush_cpu_context(), and inserting a local i-cache invalidation there. Cc: stable@vger.kernel.org Signed-off-by: Marc Zyngier Acked-by: Will Deacon Acked-by: Catalin Marinas Link: https://lore.kernel.org/r/20210303164505.68492-1-maz@kernel.org [maz: added 32bit ARM support] Signed-off-by: Marc Zyngier Signed-off-by: Greg Kroah-Hartman --- virt/kvm/arm/arm.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'virt') diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c index 986fbc3cf667..2e7d2b3f2907 100644 --- a/virt/kvm/arm/arm.c +++ b/virt/kvm/arm/arm.c @@ -373,11 +373,17 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) cpu_data = this_cpu_ptr(&kvm_host_data); /* + * We guarantee that both TLBs and I-cache are private to each + * vcpu. If detecting that a vcpu from the same VM has + * previously run on the same physical CPU, call into the + * hypervisor code to nuke the relevant contexts. + * + * We might get preempted before the vCPU actually runs, but * We might get preempted before the vCPU actually runs, but * over-invalidation doesn't affect correctness. */ if (*last_ran != vcpu->vcpu_id) { - kvm_call_hyp(__kvm_tlb_flush_local_vmid, vcpu); + kvm_call_hyp(__kvm_flush_cpu_context, vcpu); *last_ran = vcpu->vcpu_id; } -- cgit v1.2.3