[PATCH v2] arm/arm64: KVM: Perform local TLB invalidation when multiplexing vcpus on a single CPU
Marc Zyngier
marc.zyngier at arm.com
Fri Oct 28 03:27:50 PDT 2016
Architecturally, TLBs are private to the (physical) CPU they're
associated with. But when multiple vcpus from the same VM are
being multiplexed on the same CPU, the TLBs are not private
to the vcpus (and are actually shared across the VMID).
Let's consider the following scenario:
- vcpu-0 maps PA to VA
- vcpu-1 maps PA' to VA
If run on the same physical CPU, vcpu-1 can hit TLB entries generated
by vcpu-0 accesses, and access the wrong physical page.
The solution to this is to keep a per-VM map of which vcpu ran last
on each given physical CPU, and invalidate local TLBs when switching
to a different vcpu from the same VM.
Reviewed-by: Mark Rutland <mark.rutland at arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
---
Fixed comments, added Mark's RB.
arch/arm/include/asm/kvm_host.h | 11 ++++++++++-
arch/arm/include/asm/kvm_hyp.h | 1 +
arch/arm/kvm/arm.c | 35 ++++++++++++++++++++++++++++++++++-
arch/arm/kvm/hyp/switch.c | 9 +++++++++
arch/arm64/include/asm/kvm_host.h | 11 ++++++++++-
arch/arm64/kvm/hyp/switch.c | 8 ++++++++
6 files changed, 72 insertions(+), 3 deletions(-)
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 2d19e02..7290de6 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -57,6 +57,9 @@ struct kvm_arch {
/* VTTBR value associated with below pgd and vmid */
u64 vttbr;
+ /* The last vcpu id that ran on each physical CPU */
+ int __percpu *last_vcpu_ran;
+
/* Timer */
struct arch_timer_kvm timer;
@@ -174,6 +177,13 @@ struct kvm_vcpu_arch {
/* vcpu power-off state */
bool power_off;
+ /*
+ * Local TLBs potentially contain conflicting entries from
+ * another vCPU within this VMID. All entries for this VMID must
+ * be invalidated from (local) TLBs before we run this vCPU.
+ */
+ bool tlb_vmid_stale;
+
/* Don't run the guest (internal implementation need) */
bool pause;
@@ -292,7 +302,6 @@ struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
static inline void kvm_arch_hardware_unsetup(void) {}
static inline void kvm_arch_sync_events(struct kvm *kvm) {}
static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
-static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
static inline void kvm_arch_vcpu_block_finish(struct kvm_vcpu *vcpu) {}
static inline void kvm_arm_init_debug(void) {}
diff --git a/arch/arm/include/asm/kvm_hyp.h b/arch/arm/include/asm/kvm_hyp.h
index 343135e..5850890 100644
--- a/arch/arm/include/asm/kvm_hyp.h
+++ b/arch/arm/include/asm/kvm_hyp.h
@@ -71,6 +71,7 @@
#define ICIALLUIS __ACCESS_CP15(c7, 0, c1, 0)
#define ATS1CPR __ACCESS_CP15(c7, 0, c8, 0)
#define TLBIALLIS __ACCESS_CP15(c8, 0, c3, 0)
+#define TLBIALL __ACCESS_CP15(c8, 0, c7, 0)
#define TLBIALLNSNHIS __ACCESS_CP15(c8, 4, c3, 4)
#define PRRR __ACCESS_CP15(c10, 0, c2, 0)
#define NMRR __ACCESS_CP15(c10, 0, c2, 1)
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 08bb84f..e0d93cd 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -114,11 +114,18 @@ void kvm_arch_check_processor_compat(void *rtn)
*/
int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
{
- int ret = 0;
+ int ret, cpu;
if (type)
return -EINVAL;
+ kvm->arch.last_vcpu_ran = alloc_percpu(typeof(*kvm->arch.last_vcpu_ran));
+ if (!kvm->arch.last_vcpu_ran)
+ return -ENOMEM;
+
+ for_each_possible_cpu(cpu)
+ *per_cpu_ptr(kvm->arch.last_vcpu_ran, cpu) = -1;
+
ret = kvm_alloc_stage2_pgd(kvm);
if (ret)
goto out_fail_alloc;
@@ -141,6 +148,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
out_free_stage2_pgd:
kvm_free_stage2_pgd(kvm);
out_fail_alloc:
+ free_percpu(kvm->arch.last_vcpu_ran);
+ kvm->arch.last_vcpu_ran = NULL;
return ret;
}
@@ -168,6 +177,9 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
{
int i;
+ free_percpu(kvm->arch.last_vcpu_ran);
+ kvm->arch.last_vcpu_ran = NULL;
+
for (i = 0; i < KVM_MAX_VCPUS; ++i) {
if (kvm->vcpus[i]) {
kvm_arch_vcpu_free(kvm->vcpus[i]);
@@ -310,6 +322,27 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
return 0;
}
+void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu)
+{
+ int *last_ran;
+
+ last_ran = per_cpu_ptr(vcpu->kvm->arch.last_vcpu_ran, cpu);
+
+ /*
+ * We might get preempted before the vCPU actually runs, but
+ * this is fine. Our TLBI stays pending until we actually make
+ * it to __activate_vm, so we won't miss a TLBI. If another
+ * vCPU gets scheduled, it will see our vcpu_id in last_ran,
+ * and pend a TLBI for itself.
+ */
+ if (*last_ran != vcpu->vcpu_id) {
+ if (*last_ran != -1)
+ vcpu->arch.tlb_vmid_stale = true;
+
+ *last_ran = vcpu->vcpu_id;
+ }
+}
+
void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
{
vcpu->cpu = cpu;
diff --git a/arch/arm/kvm/hyp/switch.c b/arch/arm/kvm/hyp/switch.c
index 92678b7..a411762 100644
--- a/arch/arm/kvm/hyp/switch.c
+++ b/arch/arm/kvm/hyp/switch.c
@@ -75,6 +75,15 @@ static void __hyp_text __activate_vm(struct kvm_vcpu *vcpu)
{
struct kvm *kvm = kern_hyp_va(vcpu->kvm);
write_sysreg(kvm->arch.vttbr, VTTBR);
+ if (vcpu->arch.tlb_vmid_stale) {
+ /* Force vttbr to be written */
+ isb();
+ /* Local invalidate only for this VMID */
+ write_sysreg(0, TLBIALL);
+ dsb(nsh);
+ vcpu->arch.tlb_vmid_stale = false;
+ }
+
write_sysreg(vcpu->arch.midr, VPIDR);
}
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index bd94e67..0f62829 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -62,6 +62,9 @@ struct kvm_arch {
/* VTTBR value associated with above pgd and vmid */
u64 vttbr;
+ /* The last vcpu id that ran on each physical CPU */
+ int __percpu *last_vcpu_ran;
+
/* The maximum number of vCPUs depends on the used GIC model */
int max_vcpus;
@@ -252,6 +255,13 @@ struct kvm_vcpu_arch {
/* vcpu power-off state */
bool power_off;
+ /*
+ * Local TLBs potentially contain conflicting entries from
+ * another vCPU within this VMID. All entries for this VMID must
+ * be invalidated from (local) TLBs before we run this vCPU.
+ */
+ bool tlb_vmid_stale;
+
/* Don't run the guest (internal implementation need) */
bool pause;
@@ -368,7 +378,6 @@ static inline void __cpu_reset_hyp_mode(unsigned long vector_ptr,
static inline void kvm_arch_hardware_unsetup(void) {}
static inline void kvm_arch_sync_events(struct kvm *kvm) {}
static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
-static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
static inline void kvm_arch_vcpu_block_finish(struct kvm_vcpu *vcpu) {}
void kvm_arm_init_debug(void);
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 83037cd..99d0f33 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -131,6 +131,14 @@ static void __hyp_text __activate_vm(struct kvm_vcpu *vcpu)
{
struct kvm *kvm = kern_hyp_va(vcpu->kvm);
write_sysreg(kvm->arch.vttbr, vttbr_el2);
+ if (vcpu->arch.tlb_vmid_stale) {
+ /* Force vttbr_el2 to be written */
+ isb();
+ /* Local invalidate only for this VMID */
+ asm volatile("tlbi vmalle1" : : );
+ dsb(nsh);
+ vcpu->arch.tlb_vmid_stale = false;
+ }
}
static void __hyp_text __deactivate_vm(struct kvm_vcpu *vcpu)
--
2.1.4
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