diff options
Diffstat (limited to 'arch/x86/kvm/x86.c')
| -rw-r--r-- | arch/x86/kvm/x86.c | 87 |
1 files changed, 36 insertions, 51 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index b9a8c8af9713..dca2c3333ef2 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10789,7 +10789,18 @@ static void kvm_mmu_slot_apply_flags(struct kvm *kvm, /* * Nothing more to do for RO slots (which can't be dirtied and can't be - * made writable) or CREATE/MOVE/DELETE of a slot. See comments below. + * made writable) or CREATE/MOVE/DELETE of a slot. + * + * For a memslot with dirty logging disabled: + * CREATE: No dirty mappings will already exist. + * MOVE/DELETE: The old mappings will already have been cleaned up by + * kvm_arch_flush_shadow_memslot() + * + * For a memslot with dirty logging enabled: + * CREATE: No shadow pages exist, thus nothing to write-protect + * and no dirty bits to clear. + * MOVE/DELETE: The old mappings will already have been cleaned up by + * kvm_arch_flush_shadow_memslot(). */ if ((change != KVM_MR_FLAGS_ONLY) || (new->flags & KVM_MEM_READONLY)) return; @@ -10802,55 +10813,31 @@ static void kvm_mmu_slot_apply_flags(struct kvm *kvm, if (WARN_ON_ONCE(!((old->flags ^ new->flags) & KVM_MEM_LOG_DIRTY_PAGES))) return; - /* - * Dirty logging tracks sptes in 4k granularity, meaning that large - * sptes have to be split. If live migration is successful, the guest - * in the source machine will be destroyed and large sptes will be - * created in the destination. However, if the guest continues to run - * in the source machine (for example if live migration fails), small - * sptes will remain around and cause bad performance. - * - * Scan sptes if dirty logging has been stopped, dropping those - * which can be collapsed into a single large-page spte. Later - * page faults will create the large-page sptes. - * - * There is no need to do this in any of the following cases: - * CREATE: No dirty mappings will already exist. - * MOVE/DELETE: The old mappings will already have been cleaned up by - * kvm_arch_flush_shadow_memslot() - */ - if (!log_dirty_pages) + if (!log_dirty_pages) { + /* + * Dirty logging tracks sptes in 4k granularity, meaning that + * large sptes have to be split. If live migration succeeds, + * the guest in the source machine will be destroyed and large + * sptes will be created in the destination. However, if the + * guest continues to run in the source machine (for example if + * live migration fails), small sptes will remain around and + * cause bad performance. + * + * Scan sptes if dirty logging has been stopped, dropping those + * which can be collapsed into a single large-page spte. Later + * page faults will create the large-page sptes. + */ kvm_mmu_zap_collapsible_sptes(kvm, new); - - /* - * Enable or disable dirty logging for the slot. - * - * For KVM_MR_DELETE and KVM_MR_MOVE, the shadow pages of the old - * slot have been zapped so no dirty logging updates are needed for - * the old slot. - * For KVM_MR_CREATE and KVM_MR_MOVE, once the new slot is visible - * any mappings that might be created in it will consume the - * properties of the new slot and do not need to be updated here. - * - * When PML is enabled, the kvm_x86_ops dirty logging hooks are - * called to enable/disable dirty logging. - * - * When disabling dirty logging with PML enabled, the D-bit is set - * for sptes in the slot in order to prevent unnecessary GPA - * logging in the PML buffer (and potential PML buffer full VMEXIT). - * This guarantees leaving PML enabled for the guest's lifetime - * won't have any additional overhead from PML when the guest is - * running with dirty logging disabled. - * - * When enabling dirty logging, large sptes are write-protected - * so they can be split on first write. New large sptes cannot - * be created for this slot until the end of the logging. - * See the comments in fast_page_fault(). - * For small sptes, nothing is done if the dirty log is in the - * initial-all-set state. Otherwise, depending on whether pml - * is enabled the D-bit or the W-bit will be cleared. - */ - if (log_dirty_pages) { + } else { + /* + * Large sptes are write-protected so they can be split on first + * write. New large sptes cannot be created for this slot until + * the end of the logging. See the comments in fast_page_fault(). + * + * For small sptes, nothing is done if the dirty log is in the + * initial-all-set state. Otherwise, depending on whether pml + * is enabled the D-bit or the W-bit will be cleared. + */ if (kvm_x86_ops.cpu_dirty_log_size) { if (!kvm_dirty_log_manual_protect_and_init_set(kvm)) kvm_mmu_slot_leaf_clear_dirty(kvm, new); @@ -10870,8 +10857,6 @@ static void kvm_mmu_slot_apply_flags(struct kvm *kvm, */ kvm_mmu_slot_remove_write_access(kvm, new, level); } - } else if (kvm_x86_ops.cpu_dirty_log_size) { - kvm_mmu_slot_set_dirty(kvm, new); } } |