From: Brendan Jackman Currently the tracking of the need to flush L1D for L1TF is tracked by two bits: one per-CPU and one per-vCPU. The per-vCPU bit is always set when the vCPU shows up on a core, so there is no interesting state that's truly per-vCPU. Indeed, this is a requirement, since L1D is a part of the physical CPU. So simplify this by combining the two bits. The vCPU bit was being written from preemption-enabled regions. To play nice with those cases, wrap all calls from KVM and use a raw write so that request a flush with preemption enabled doesn't trigger what would effectively be DEBUG_PREEMPT false positives. Preemption doesn't need to be disabled, as kvm_arch_vcpu_load() will mark the new CPU as needing a flush if the vCPU task is migrated, or if userspace runs the vCPU on a different task. Signed-off-by: Brendan Jackman [sean: put raw write in KVM instead of in a hardirq.h variant] Signed-off-by: Sean Christopherson --- arch/x86/include/asm/kvm_host.h | 3 --- arch/x86/kvm/mmu/mmu.c | 2 +- arch/x86/kvm/vmx/nested.c | 2 +- arch/x86/kvm/vmx/vmx.c | 20 +++++--------------- arch/x86/kvm/x86.c | 6 +++--- arch/x86/kvm/x86.h | 14 ++++++++++++++ 6 files changed, 24 insertions(+), 23 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 48598d017d6f..fcdc65ab13d8 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1055,9 +1055,6 @@ struct kvm_vcpu_arch { /* be preempted when it's in kernel-mode(cpl=0) */ bool preempted_in_kernel; - /* Flush the L1 Data cache for L1TF mitigation on VMENTER */ - bool l1tf_flush_l1d; - /* Host CPU on which VM-entry was most recently attempted */ int last_vmentry_cpu; diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 18d69d48bc55..4e016582adc7 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4859,7 +4859,7 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code, */ BUILD_BUG_ON(lower_32_bits(PFERR_SYNTHETIC_MASK)); - vcpu->arch.l1tf_flush_l1d = true; + kvm_request_l1tf_flush_l1d(); if (!flags) { trace_kvm_page_fault(vcpu, fault_address, error_code); diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index b0cd745518b4..6f2f969d19f9 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -3828,7 +3828,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch) goto vmentry_failed; /* Hide L1D cache contents from the nested guest. */ - vcpu->arch.l1tf_flush_l1d = true; + kvm_request_l1tf_flush_l1d(); /* * Must happen outside of nested_vmx_enter_non_root_mode() as it will diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 1b5540105e4b..f87af1836ea1 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -395,26 +395,16 @@ static noinstr void vmx_l1d_flush(struct kvm_vcpu *vcpu) * 'always' */ if (static_branch_likely(&vmx_l1d_flush_cond)) { - bool flush_l1d; - /* - * Clear the per-vcpu flush bit, it gets set again if the vCPU + * Clear the per-cpu flush bit, it gets set again if the vCPU * is reloaded, i.e. if the vCPU is scheduled out or if KVM * exits to userspace, or if KVM reaches one of the unsafe - * VMEXIT handlers, e.g. if KVM calls into the emulator. + * VMEXIT handlers, e.g. if KVM calls into the emulator, + * or from the interrupt handlers. */ - flush_l1d = vcpu->arch.l1tf_flush_l1d; - vcpu->arch.l1tf_flush_l1d = false; - - /* - * Clear the per-cpu flush bit, it gets set again from - * the interrupt handlers. - */ - flush_l1d |= kvm_get_cpu_l1tf_flush_l1d(); + if (!kvm_get_cpu_l1tf_flush_l1d()) + return; kvm_clear_cpu_l1tf_flush_l1d(); - - if (!flush_l1d) - return; } vcpu->stat.l1d_flush++; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index b4b5d2d09634..851f078cd5ca 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5189,7 +5189,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) { struct kvm_pmu *pmu = vcpu_to_pmu(vcpu); - vcpu->arch.l1tf_flush_l1d = true; + kvm_request_l1tf_flush_l1d(); if (vcpu->scheduled_out && pmu->version && pmu->event_count) { pmu->need_cleanup = true; @@ -7999,7 +7999,7 @@ int kvm_write_guest_virt_system(struct kvm_vcpu *vcpu, gva_t addr, void *val, unsigned int bytes, struct x86_exception *exception) { /* kvm_write_guest_virt_system can pull in tons of pages. */ - vcpu->arch.l1tf_flush_l1d = true; + kvm_request_l1tf_flush_l1d(); return kvm_write_guest_virt_helper(addr, val, bytes, vcpu, PFERR_WRITE_MASK, exception); @@ -9395,7 +9395,7 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, return handle_emulation_failure(vcpu, emulation_type); } - vcpu->arch.l1tf_flush_l1d = true; + kvm_request_l1tf_flush_l1d(); if (!(emulation_type & EMULTYPE_NO_DECODE)) { kvm_clear_exception_queue(vcpu); diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h index f3dc77f006f9..cd67ccbb747f 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -420,6 +420,20 @@ static inline bool kvm_check_has_quirk(struct kvm *kvm, u64 quirk) return !(kvm->arch.disabled_quirks & quirk); } +static __always_inline void kvm_request_l1tf_flush_l1d(void) +{ +#if IS_ENABLED(CONFIG_CPU_MITIGATIONS) && IS_ENABLED(CONFIG_KVM_INTEL) + /* + * Use a raw write to set the per-CPU flag, as KVM will ensure a flush + * even if preemption is currently enabled.. If the current vCPU task + * is migrated to a different CPU (or userspace runs the vCPU on a + * different task) before the next VM-Entry, then kvm_arch_vcpu_load() + * will request a flush on the new CPU. + */ + raw_cpu_write(irq_stat.kvm_cpu_l1tf_flush_l1d, 1); +#endif +} + void kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip); u64 get_kvmclock_ns(struct kvm *kvm); -- 2.51.1.930.gacf6e81ea2-goog