From 9078210ef4016539c909fb67164d3f1c27323d8b Mon Sep 17 00:00:00 2001 From: James Hogan Date: Tue, 25 Oct 2016 16:08:19 +0100 Subject: [PATCH] KVM: MIPS: Fix lazy user ASID regenerate for SMP MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit kvm_mips_check_asids() runs before entering the guest and performs lazy regeneration of host ASID for guest usermode, using last_user_gasid to track the last guest ASID in the VCPU that was used by guest usermode on any host CPU. last_user_gasid is reset after performing the lazy ASID regeneration on the current CPU, and by kvm_arch_vcpu_load() if the host ASID for guest usermode is regenerated due to staleness (to cancel outstanding lazy ASID regenerations). Unfortunately neither case handles SMP hosts correctly: - When the lazy ASID regeneration is performed it should apply to all CPUs (as last_user_gasid does), so reset the ASID on other CPUs to zero to trigger regeneration when the VCPU is next loaded on those CPUs. - When the ASID is found to be stale on the current CPU, we should not cancel lazy ASID regenerations globally, so drop the reset of last_user_gasid altogether here. Both cases would require a guest ASID change and two host CPU migrations (and in the latter case one of the CPUs to start a new ASID cycle) before guest usermode could potentially access stale user pages from a previously running ASID in the same VCPU. Fixes: 25b08c7fb0e4 ("KVM: MIPS: Invalidate TLB by regenerating ASIDs") Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: "Radim Krčmář Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Signed-off-by: Paolo Bonzini --- arch/mips/kvm/mips.c | 5 ++++- arch/mips/kvm/mmu.c | 4 ---- 2 files changed, 4 insertions(+), 5 deletions(-) diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index 622037d851a3..06a60b19acfb 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -426,7 +426,7 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu, static void kvm_mips_check_asids(struct kvm_vcpu *vcpu) { struct mips_coproc *cop0 = vcpu->arch.cop0; - int cpu = smp_processor_id(); + int i, cpu = smp_processor_id(); unsigned int gasid; /* @@ -442,6 +442,9 @@ static void kvm_mips_check_asids(struct kvm_vcpu *vcpu) vcpu); vcpu->arch.guest_user_asid[cpu] = vcpu->arch.guest_user_mm.context.asid[cpu]; + for_each_possible_cpu(i) + if (i != cpu) + vcpu->arch.guest_user_asid[cpu] = 0; vcpu->arch.last_user_gasid = gasid; } } diff --git a/arch/mips/kvm/mmu.c b/arch/mips/kvm/mmu.c index 03883ba806e2..3b677c851be0 100644 --- a/arch/mips/kvm/mmu.c +++ b/arch/mips/kvm/mmu.c @@ -260,13 +260,9 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) if ((vcpu->arch.guest_user_asid[cpu] ^ asid_cache(cpu)) & asid_version_mask(cpu)) { - u32 gasid = kvm_read_c0_guest_entryhi(vcpu->arch.cop0) & - KVM_ENTRYHI_ASID; - kvm_get_new_mmu_context(&vcpu->arch.guest_user_mm, cpu, vcpu); vcpu->arch.guest_user_asid[cpu] = vcpu->arch.guest_user_mm.context.asid[cpu]; - vcpu->arch.last_user_gasid = gasid; newasid++; kvm_debug("[%d]: cpu_context: %#lx\n", cpu, -- 2.39.5