diff options
Diffstat (limited to 'include/linux/kvm_host.h')
| -rw-r--r-- | include/linux/kvm_host.h | 34 |
1 files changed, 29 insertions, 5 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index c38cc5eb7e73..640a03642766 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -28,6 +28,7 @@ #include <linux/irqbypass.h> #include <linux/swait.h> #include <linux/refcount.h> +#include <linux/nospec.h> #include <asm/signal.h> #include <linux/kvm.h> @@ -48,6 +49,27 @@ */ #define KVM_MEMSLOT_INVALID (1UL << 16) +/* + * Bit 63 of the memslot generation number is an "update in-progress flag", + * e.g. is temporarily set for the duration of install_new_memslots(). + * This flag effectively creates a unique generation number that is used to + * mark cached memslot data, e.g. MMIO accesses, as potentially being stale, + * i.e. may (or may not) have come from the previous memslots generation. + * + * This is necessary because the actual memslots update is not atomic with + * respect to the generation number update. Updating the generation number + * first would allow a vCPU to cache a spte from the old memslots using the + * new generation number, and updating the generation number after switching + * to the new memslots would allow cache hits using the old generation number + * to reference the defunct memslots. + * + * This mechanism is used to prevent getting hits in KVM's caches while a + * memslot update is in-progress, and to prevent cache hits *after* updating + * the actual generation number against accesses that were inserted into the + * cache *before* the memslots were updated. + */ +#define KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS BIT_ULL(63) + /* Two fragments for cross MMIO pages. */ #define KVM_MAX_MMIO_FRAGMENTS 2 @@ -492,10 +514,10 @@ static inline struct kvm_io_bus *kvm_get_bus(struct kvm *kvm, enum kvm_bus idx) static inline struct kvm_vcpu *kvm_get_vcpu(struct kvm *kvm, int i) { - /* Pairs with smp_wmb() in kvm_vm_ioctl_create_vcpu, in case - * the caller has read kvm->online_vcpus before (as is the case - * for kvm_for_each_vcpu, for example). - */ + int num_vcpus = atomic_read(&kvm->online_vcpus); + i = array_index_nospec(i, num_vcpus); + + /* Pairs with smp_wmb() in kvm_vm_ioctl_create_vcpu. */ smp_rmb(); return kvm->vcpus[i]; } @@ -579,6 +601,7 @@ void kvm_put_kvm(struct kvm *kvm); static inline struct kvm_memslots *__kvm_memslots(struct kvm *kvm, int as_id) { + as_id = array_index_nospec(as_id, KVM_ADDRESS_SPACE_NUM); return srcu_dereference_check(kvm->memslots[as_id], &kvm->srcu, lockdep_is_held(&kvm->slots_lock) || !refcount_read(&kvm->users_count)); @@ -634,7 +657,7 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free, struct kvm_memory_slot *dont); int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot, unsigned long npages); -void kvm_arch_memslots_updated(struct kvm *kvm, struct kvm_memslots *slots); +void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen); int kvm_arch_prepare_memory_region(struct kvm *kvm, struct kvm_memory_slot *memslot, const struct kvm_userspace_memory_region *mem, @@ -1182,6 +1205,7 @@ extern bool kvm_rebooting; extern unsigned int halt_poll_ns; extern unsigned int halt_poll_ns_grow; +extern unsigned int halt_poll_ns_grow_start; extern unsigned int halt_poll_ns_shrink; struct kvm_device { |