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x86/KVM/VMX: Add L1D flush logic

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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 ]

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>
This commit is contained in:
Paolo Bonzini
2018-07-02 13:07:14 +02:00
committed by Thomas Gleixner
parent 3fa045be4c
commit c595ceee45
4 changed files with 34 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
arch/x86/kvm/x86.c
View File

@@ -195,6 +195,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
{ "irq_injections", VCPU_STAT(irq_injections) },
{ "nmi_injections", VCPU_STAT(nmi_injections) },
{ "req_event", VCPU_STAT(req_event) },
{ "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) },
@@ -4874,6 +4875,9 @@ static int emulator_write_std(struct x86_emulate_ctxt *ctxt, gva_t addr, void *v
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);
}
@@ -6050,6 +6054,8 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
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.
@@ -7579,6 +7585,7 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
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)) {
@@ -8698,6 +8705,7 @@ void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu)
void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu)
{
vcpu->arch.l1tf_flush_l1d = true;
kvm_x86_ops->sched_in(vcpu, cpu);
}