diff options
| -rw-r--r-- | include/linux/kvm_host.h | 13 | ||||
| -rw-r--r-- | virt/kvm/kvm_main.c | 22 |
2 files changed, 34 insertions, 1 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index f30b53a07917..492d183dd7d0 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -354,6 +354,13 @@ struct kvm_vcpu { struct kvm_vcpu_stat stat; char stats_id[KVM_STATS_NAME_SIZE]; struct kvm_dirty_ring dirty_ring; + + /* + * The index of the most recently used memslot by this vCPU. It's ok + * if this becomes stale due to memslot changes since we always check + * it is a valid slot. + */ + int last_used_slot; }; /* must be called with irqs disabled */ @@ -1200,6 +1207,12 @@ try_get_memslot(struct kvm_memslots *slots, int slot_index, gfn_t gfn) if (slot_index < 0 || slot_index >= slots->used_slots) return NULL; + /* + * slot_index can come from vcpu->last_used_slot which is not kept + * in sync with userspace-controllable memslot deletion. So use nospec + * to prevent the CPU from speculating past the end of memslots[]. + */ + slot_index = array_index_nospec(slot_index, slots->used_slots); slot = &slots->memslots[slot_index]; if (gfn >= slot->base_gfn && gfn < slot->base_gfn + slot->npages) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 1984c7389787..30d322519253 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -415,6 +415,7 @@ static void kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id) vcpu->preempted = false; vcpu->ready = false; preempt_notifier_init(&vcpu->preempt_notifier, &kvm_preempt_ops); + vcpu->last_used_slot = 0; } void kvm_vcpu_destroy(struct kvm_vcpu *vcpu) @@ -2025,7 +2026,26 @@ EXPORT_SYMBOL_GPL(gfn_to_memslot); struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn) { - return __gfn_to_memslot(kvm_vcpu_memslots(vcpu), gfn); + struct kvm_memslots *slots = kvm_vcpu_memslots(vcpu); + struct kvm_memory_slot *slot; + int slot_index; + + slot = try_get_memslot(slots, vcpu->last_used_slot, gfn); + if (slot) + return slot; + + /* + * Fall back to searching all memslots. We purposely use + * search_memslots() instead of __gfn_to_memslot() to avoid + * thrashing the VM-wide last_used_index in kvm_memslots. + */ + slot = search_memslots(slots, gfn, &slot_index); + if (slot) { + vcpu->last_used_slot = slot_index; + return slot; + } + + return NULL; } EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_memslot); |