4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Paolo Bonzini pbonzini@redhat.com
commit c595ceee45707f00f64f61c54fb64ef0cc0b4e85 upstream
Add the logic for flushing L1D on VMENTER. The flush depends on the static key being enabled and the new l1tf_flush_l1d flag being set.
The flags is set: - Always, if the flush module parameter is 'always'
- Conditionally at: - Entry to vcpu_run(), i.e. after executing user space
- From the sched_in notifier, i.e. when switching to a vCPU thread.
- From vmexit handlers which are considered unsafe, i.e. where sensitive data can be brought into L1D:
- The emulator, which could be a good target for other speculative execution-based threats,
- The MMU, which can bring host page tables in the L1 cache.
- External interrupts
- Nested operations that require the MMU (see above). That is vmptrld, vmptrst, vmclear,vmwrite,vmread.
- When handling invept,invvpid
[ tglx: Split out from combo patch and reduced to a single flag ] [ dwmw2: Backported to 4.9, set l1tf_flush_l1d in svm/vmx code ]
Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Konrad Rzeszutek Wilk konrad.wilk@oracle.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: David Woodhouse dwmw@amazon.co.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/kvm_host.h | 4 ++++ arch/x86/kvm/svm.c | 2 ++ arch/x86/kvm/vmx.c | 23 ++++++++++++++++++++++- arch/x86/kvm/x86.c | 8 ++++++++ 4 files changed, 36 insertions(+), 1 deletion(-)
--- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -659,6 +659,9 @@ struct kvm_vcpu_arch {
int pending_ioapic_eoi; int pending_external_vector; + + /* Flush the L1 Data cache for L1TF mitigation on VMENTER */ + bool l1tf_flush_l1d; };
struct kvm_lpage_info { @@ -819,6 +822,7 @@ struct kvm_vcpu_stat { u64 signal_exits; u64 irq_window_exits; u64 nmi_window_exits; + u64 l1d_flush; u64 halt_exits; u64 halt_successful_poll; u64 halt_attempted_poll; --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -2124,6 +2124,8 @@ static int pf_interception(struct vcpu_s u32 error_code; int r = 1;
+ svm->vcpu.arch.l1tf_flush_l1d = true; + switch (svm->apf_reason) { default: error_code = svm->vmcb->control.exit_info_1; --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -5773,6 +5773,7 @@ static int handle_exception(struct kvm_v BUG_ON(enable_ept); cr2 = vmcs_readl(EXIT_QUALIFICATION); trace_kvm_page_fault(cr2, error_code); + vcpu->arch.l1tf_flush_l1d = true;
if (kvm_event_needs_reinjection(vcpu)) kvm_mmu_unprotect_page_virt(vcpu, cr2); @@ -8549,9 +8550,20 @@ static int vmx_handle_exit(struct kvm_vc #define L1D_CACHE_ORDER 4 static void *vmx_l1d_flush_pages;
-static void __maybe_unused vmx_l1d_flush(void) +static void vmx_l1d_flush(struct kvm_vcpu *vcpu) { int size = PAGE_SIZE << L1D_CACHE_ORDER; + bool always; + + /* + * If the mitigation mode is 'flush always', keep the flush bit + * set, otherwise clear it. It gets set again either from + * vcpu_run() or from one of the unsafe VMEXIT handlers. + */ + always = vmentry_l1d_flush == VMENTER_L1D_FLUSH_ALWAYS; + vcpu->arch.l1tf_flush_l1d = always; + + vcpu->stat.l1d_flush++;
if (static_cpu_has(X86_FEATURE_FLUSH_L1D)) { wrmsrl(MSR_IA32_FLUSH_CMD, L1D_FLUSH); @@ -8792,6 +8804,7 @@ static void vmx_handle_external_intr(str [ss]"i"(__KERNEL_DS), [cs]"i"(__KERNEL_CS) ); + vcpu->arch.l1tf_flush_l1d = true; } } STACK_FRAME_NON_STANDARD(vmx_handle_external_intr); @@ -9037,6 +9050,11 @@ static void __noclone vmx_vcpu_run(struc
vmx->__launched = vmx->loaded_vmcs->launched;
+ if (static_branch_unlikely(&vmx_l1d_should_flush)) { + if (vcpu->arch.l1tf_flush_l1d) + vmx_l1d_flush(vcpu); + } + asm( /* Store host registers */ "push %%" _ASM_DX "; push %%" _ASM_BP ";" @@ -10552,6 +10570,9 @@ static int nested_vmx_run(struct kvm_vcp
vmcs12->launch_state = 1;
+ /* Hide L1D cache contents from the nested guest. */ + vmx->vcpu.arch.l1tf_flush_l1d = true; + if (vmcs12->guest_activity_state == GUEST_ACTIVITY_HLT) return kvm_vcpu_halt(vcpu);
--- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -180,6 +180,7 @@ struct kvm_stats_debugfs_item debugfs_en { "insn_emulation_fail", VCPU_STAT(insn_emulation_fail) }, { "irq_injections", VCPU_STAT(irq_injections) }, { "nmi_injections", VCPU_STAT(nmi_injections) }, + { "l1d_flush", VCPU_STAT(l1d_flush) }, { "mmu_shadow_zapped", VM_STAT(mmu_shadow_zapped) }, { "mmu_pte_write", VM_STAT(mmu_pte_write) }, { "mmu_pte_updated", VM_STAT(mmu_pte_updated) }, @@ -4476,6 +4477,9 @@ static int emulator_write_std(struct x86 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; + return kvm_write_guest_virt_helper(addr, val, bytes, vcpu, PFERR_WRITE_MASK, exception); } @@ -5574,6 +5578,8 @@ int x86_emulate_instruction(struct kvm_v bool writeback = true; bool write_fault_to_spt = vcpu->arch.write_fault_to_shadow_pgtable;
+ vcpu->arch.l1tf_flush_l1d = true; + /* * Clear write_fault_to_shadow_pgtable here to ensure it is * never reused. @@ -6929,6 +6935,7 @@ static int vcpu_run(struct kvm_vcpu *vcp struct kvm *kvm = vcpu->kvm;
vcpu->srcu_idx = srcu_read_lock(&kvm->srcu); + vcpu->arch.l1tf_flush_l1d = true;
for (;;) { if (kvm_vcpu_running(vcpu)) { @@ -7899,6 +7906,7 @@ void kvm_arch_vcpu_uninit(struct kvm_vcp
void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) { + vcpu->arch.l1tf_flush_l1d = true; kvm_x86_ops->sched_in(vcpu, cpu); }