diff options
| -rw-r--r-- | include/linux/kvm_host.h | 9 | ||||
| -rw-r--r-- | virt/kvm/Kconfig | 6 | ||||
| -rw-r--r-- | virt/kvm/kvm_main.c | 80 |
3 files changed, 95 insertions, 0 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 26f106022c88..3b934cc94cc8 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -611,6 +611,15 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext); int kvm_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log, int *is_dirty); + +int kvm_get_dirty_log_protect(struct kvm *kvm, + struct kvm_dirty_log *log, bool *is_dirty); + +void kvm_arch_mmu_write_protect_pt_masked(struct kvm *kvm, + struct kvm_memory_slot *slot, + gfn_t gfn_offset, + unsigned long mask); + int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log); diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig index 3796a2132a06..314950c51d9f 100644 --- a/virt/kvm/Kconfig +++ b/virt/kvm/Kconfig @@ -40,3 +40,9 @@ config KVM_VFIO config HAVE_KVM_ARCH_TLB_FLUSH_ALL bool + +config HAVE_KVM_ARCH_DIRTY_LOG_PROTECT + bool + +config KVM_GENERIC_DIRTYLOG_READ_PROTECT + bool diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index d03bd2255801..246cf291c6fd 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -995,6 +995,86 @@ out: } EXPORT_SYMBOL_GPL(kvm_get_dirty_log); +#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT +/** + * kvm_get_dirty_log_protect - get a snapshot of dirty pages, and if any pages + * are dirty write protect them for next write. + * @kvm: pointer to kvm instance + * @log: slot id and address to which we copy the log + * @is_dirty: flag set if any page is dirty + * + * We need to keep it in mind that VCPU threads can write to the bitmap + * concurrently. So, to avoid losing track of dirty pages we keep the + * following order: + * + * 1. Take a snapshot of the bit and clear it if needed. + * 2. Write protect the corresponding page. + * 3. Copy the snapshot to the userspace. + * 4. Upon return caller flushes TLB's if needed. + * + * Between 2 and 4, the guest may write to the page using the remaining TLB + * entry. This is not a problem because the page is reported dirty using + * the snapshot taken before and step 4 ensures that writes done after + * exiting to userspace will be logged for the next call. + * + */ +int kvm_get_dirty_log_protect(struct kvm *kvm, + struct kvm_dirty_log *log, bool *is_dirty) +{ + struct kvm_memory_slot *memslot; + int r, i; + unsigned long n; + unsigned long *dirty_bitmap; + unsigned long *dirty_bitmap_buffer; + + r = -EINVAL; + if (log->slot >= KVM_USER_MEM_SLOTS) + goto out; + + memslot = id_to_memslot(kvm->memslots, log->slot); + + dirty_bitmap = memslot->dirty_bitmap; + r = -ENOENT; + if (!dirty_bitmap) + goto out; + + n = kvm_dirty_bitmap_bytes(memslot); + + dirty_bitmap_buffer = dirty_bitmap + n / sizeof(long); + memset(dirty_bitmap_buffer, 0, n); + + spin_lock(&kvm->mmu_lock); + *is_dirty = false; + for (i = 0; i < n / sizeof(long); i++) { + unsigned long mask; + gfn_t offset; + + if (!dirty_bitmap[i]) + continue; + + *is_dirty = true; + + mask = xchg(&dirty_bitmap[i], 0); + dirty_bitmap_buffer[i] = mask; + + offset = i * BITS_PER_LONG; + kvm_arch_mmu_write_protect_pt_masked(kvm, memslot, offset, + mask); + } + + spin_unlock(&kvm->mmu_lock); + + r = -EFAULT; + if (copy_to_user(log->dirty_bitmap, dirty_bitmap_buffer, n)) + goto out; + + r = 0; +out: + return r; +} +EXPORT_SYMBOL_GPL(kvm_get_dirty_log_protect); +#endif + bool kvm_largepages_enabled(void) { return largepages_enabled; |