On Mon, 2021-10-18 at 13:53 -0400, Paolo Bonzini wrote:
> From: David Stevens <stevensd@xxxxxxxxxxxx>
>
> Unify the flags for rmaps and page tracking data, using a
> single flag in struct kvm_arch and a single loop to go
> over all the address spaces and memslots. This avoids
> code duplication between alloc_all_memslots_rmaps and
> kvm_page_track_enable_mmu_write_tracking.
>
> Signed-off-by: David Stevens <stevensd@xxxxxxxxxxxx>
> [This patch is the delta between David's v2 and v3, with conflicts
> fixed and my own commit message. - Paolo]
> Co-developed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 17 ++----
> arch/x86/include/asm/kvm_page_track.h | 3 +-
> arch/x86/kvm/mmu.h | 16 ++++--
> arch/x86/kvm/mmu/mmu.c | 78 +++++++++++++++++++++------
> arch/x86/kvm/mmu/page_track.c | 59 ++++++--------------
> arch/x86/kvm/x86.c | 47 +---------------
> 6 files changed, 97 insertions(+), 123 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 88f0326c184a..80f4b8a9233c 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1212,18 +1212,11 @@ struct kvm_arch {
> #endif /* CONFIG_X86_64 */
>
> /*
> - * If set, rmaps have been allocated for all memslots and should be
> - * allocated for any newly created or modified memslots.
> + * If set, at least one shadow root has been allocated. This flag
> + * is used as one input when determining whether certain memslot
> + * related allocations are necessary.
> */
> - bool memslots_have_rmaps;
> -
> - /*
> - * Set when the KVM mmu needs guest write access page tracking. If
> - * set, the necessary gfn_track arrays have been allocated for
> - * all memslots and should be allocated for any newly created or
> - * modified memslots.
> - */
> - bool memslots_mmu_write_tracking;
> + bool shadow_root_alloced;
>
> #if IS_ENABLED(CONFIG_HYPERV)
> hpa_t hv_root_tdp;
> @@ -1946,7 +1939,7 @@ static inline int kvm_cpu_get_apicid(int mps_cpu)
>
> int kvm_cpu_dirty_log_size(void);
>
> -int alloc_all_memslots_rmaps(struct kvm *kvm);
> +int memslot_rmap_alloc(struct kvm_memory_slot *slot, unsigned long npages);
>
> #define KVM_CLOCK_VALID_FLAGS \
> (KVM_CLOCK_TSC_STABLE | KVM_CLOCK_REALTIME | KVM_CLOCK_HOST_TSC)
> diff --git a/arch/x86/include/asm/kvm_page_track.h b/arch/x86/include/asm/kvm_page_track.h
> index 79d84a94f8eb..9d4a3b1b25b9 100644
> --- a/arch/x86/include/asm/kvm_page_track.h
> +++ b/arch/x86/include/asm/kvm_page_track.h
> @@ -49,7 +49,8 @@ struct kvm_page_track_notifier_node {
> int kvm_page_track_init(struct kvm *kvm);
> void kvm_page_track_cleanup(struct kvm *kvm);
>
> -int kvm_page_track_enable_mmu_write_tracking(struct kvm *kvm);
> +bool kvm_page_track_write_tracking_enabled(struct kvm *kvm);
> +int kvm_page_track_write_tracking_alloc(struct kvm_memory_slot *slot);
>
> void kvm_page_track_free_memslot(struct kvm_memory_slot *slot);
> int kvm_page_track_create_memslot(struct kvm *kvm,
> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
> index e53ef2ae958f..1ae70efedcf4 100644
> --- a/arch/x86/kvm/mmu.h
> +++ b/arch/x86/kvm/mmu.h
> @@ -303,14 +303,20 @@ int kvm_arch_write_log_dirty(struct kvm_vcpu *vcpu);
> int kvm_mmu_post_init_vm(struct kvm *kvm);
> void kvm_mmu_pre_destroy_vm(struct kvm *kvm);
>
> -static inline bool kvm_memslots_have_rmaps(struct kvm *kvm)
> +static inline bool kvm_shadow_root_alloced(struct kvm *kvm)
> {
> /*
> - * Read memslot_have_rmaps before rmap pointers. Hence, threads reading
> - * memslots_have_rmaps in any lock context are guaranteed to see the
> - * pointers. Pairs with smp_store_release in alloc_all_memslots_rmaps.
> + * Read shadow_root_alloced before related pointers. Hence, threads
> + * reading shadow_root_alloced in any lock context are guaranteed to
> + * see the pointers. Pairs with smp_store_release in
> + * mmu_first_shadow_root_alloc.
> */
> - return smp_load_acquire(&kvm->arch.memslots_have_rmaps);
> + return smp_load_acquire(&kvm->arch.shadow_root_alloced);
> +}
> +
> +static inline bool kvm_memslots_have_rmaps(struct kvm *kvm)
> +{
> + return !kvm->arch.tdp_mmu_enabled || kvm_shadow_root_alloced(kvm);
> }
Note that this breaks 32 bit build - kvm->arch.tdp_mmu_enabled is not defined.
Best regards,
Maxim Levitsky
>
> static inline gfn_t gfn_to_index(gfn_t gfn, gfn_t base_gfn, int level)
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 29e7a4bb26e9..757e2a1ed149 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3397,6 +3397,67 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
> return r;
> }
>
> +static int mmu_first_shadow_root_alloc(struct kvm *kvm)
> +{
> + struct kvm_memslots *slots;
> + struct kvm_memory_slot *slot;
> + int r = 0, i;
> +
> + /*
> + * Check if this is the first shadow root being allocated before
> + * taking the lock.
> + */
> + if (kvm_shadow_root_alloced(kvm))
> + return 0;
> +
> + mutex_lock(&kvm->slots_arch_lock);
> +
> + /* Recheck, under the lock, whether this is the first shadow root. */
> + if (kvm_shadow_root_alloced(kvm))
> + goto out_unlock;
> +
> + /*
> + * Check if anything actually needs to be allocated, e.g. all metadata
> + * will be allocated upfront if TDP is disabled.
> + */
> + if (kvm_memslots_have_rmaps(kvm) &&
> + kvm_page_track_write_tracking_enabled(kvm))
> + goto out_success;
> +
> + for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
> + slots = __kvm_memslots(kvm, i);
> + kvm_for_each_memslot(slot, slots) {
> + /*
> + * Both of these functions are no-ops if the target is
> + * already allocated, so unconditionally calling both
> + * is safe. Intentionally do NOT free allocations on
> + * failure to avoid having to track which allocations
> + * were made now versus when the memslot was created.
> + * The metadata is guaranteed to be freed when the slot
> + * is freed, and will be kept/used if userspace retries
> + * KVM_RUN instead of killing the VM.
> + */
> + r = memslot_rmap_alloc(slot, slot->npages);
> + if (r)
> + goto out_unlock;
> + r = kvm_page_track_write_tracking_alloc(slot);
> + if (r)
> + goto out_unlock;
> + }
> + }
> +
> + /*
> + * Ensure that shadow_root_alloced becomes true strictly after
> + * all the related pointers are set.
> + */
> +out_success:
> + smp_store_release(&kvm->arch.shadow_root_alloced, true);
> +
> +out_unlock:
> + mutex_unlock(&kvm->slots_arch_lock);
> + return r;
> +}
> +
> static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
> {
> struct kvm_mmu *mmu = vcpu->arch.mmu;
> @@ -3427,11 +3488,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
> }
> }
>
> - r = alloc_all_memslots_rmaps(vcpu->kvm);
> - if (r)
> - return r;
> -
> - r = kvm_page_track_enable_mmu_write_tracking(vcpu->kvm);
> + r = mmu_first_shadow_root_alloc(vcpu->kvm);
> if (r)
> return r;
>
> @@ -5604,16 +5661,7 @@ void kvm_mmu_init_vm(struct kvm *kvm)
>
> spin_lock_init(&kvm->arch.mmu_unsync_pages_lock);
>
> - if (!kvm_mmu_init_tdp_mmu(kvm))
> - /*
> - * No smp_load/store wrappers needed here as we are in
> - * VM init and there cannot be any memslots / other threads
> - * accessing this struct kvm yet.
> - */
> - kvm->arch.memslots_have_rmaps = true;
> -
> - if (!tdp_enabled)
> - kvm->arch.memslots_mmu_write_tracking = true;
> + kvm_mmu_init_tdp_mmu(kvm);
>
> node->track_write = kvm_mmu_pte_write;
> node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
> diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
> index 357605809825..5e0684460930 100644
> --- a/arch/x86/kvm/mmu/page_track.c
> +++ b/arch/x86/kvm/mmu/page_track.c
> @@ -19,14 +19,10 @@
> #include "mmu.h"
> #include "mmu_internal.h"
>
> -static bool write_tracking_enabled(struct kvm *kvm)
> +bool kvm_page_track_write_tracking_enabled(struct kvm *kvm)
> {
> - /*
> - * Read memslots_mmu_write_tracking before gfn_track pointers. Pairs
> - * with smp_store_release in kvm_page_track_enable_mmu_write_tracking.
> - */
> return IS_ENABLED(CONFIG_KVM_EXTERNAL_WRITE_TRACKING) ||
> - smp_load_acquire(&kvm->arch.memslots_mmu_write_tracking);
> + !tdp_enabled || kvm_shadow_root_alloced(kvm);
> }
>
> void kvm_page_track_free_memslot(struct kvm_memory_slot *slot)
> @@ -46,7 +42,8 @@ int kvm_page_track_create_memslot(struct kvm *kvm,
> int i;
>
> for (i = 0; i < KVM_PAGE_TRACK_MAX; i++) {
> - if (i == KVM_PAGE_TRACK_WRITE && !write_tracking_enabled(kvm))
> + if (i == KVM_PAGE_TRACK_WRITE &&
> + !kvm_page_track_write_tracking_enabled(kvm))
> continue;
>
> slot->arch.gfn_track[i] =
> @@ -70,45 +67,18 @@ static inline bool page_track_mode_is_valid(enum kvm_page_track_mode mode)
> return true;
> }
>
> -int kvm_page_track_enable_mmu_write_tracking(struct kvm *kvm)
> +int kvm_page_track_write_tracking_alloc(struct kvm_memory_slot *slot)
> {
> - struct kvm_memslots *slots;
> - struct kvm_memory_slot *slot;
> - unsigned short **gfn_track;
> - int i;
> + unsigned short *gfn_track;
>
> - if (write_tracking_enabled(kvm))
> + if (slot->arch.gfn_track[KVM_PAGE_TRACK_WRITE])
> return 0;
>
> - mutex_lock(&kvm->slots_arch_lock);
> -
> - if (write_tracking_enabled(kvm)) {
> - mutex_unlock(&kvm->slots_arch_lock);
> - return 0;
> - }
> -
> - for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
> - slots = __kvm_memslots(kvm, i);
> - kvm_for_each_memslot(slot, slots) {
> - gfn_track = slot->arch.gfn_track + KVM_PAGE_TRACK_WRITE;
> - if (*gfn_track)
> - continue;
> -
> - *gfn_track = vcalloc(slot->npages, sizeof(**gfn_track));
> - if (*gfn_track == NULL) {
> - mutex_unlock(&kvm->slots_arch_lock);
> - return -ENOMEM;
> - }
> - }
> - }
> -
> - /*
> - * Ensure that memslots_mmu_write_tracking becomes true strictly
> - * after all the pointers are set.
> - */
> - smp_store_release(&kvm->arch.memslots_mmu_write_tracking, true);
> - mutex_unlock(&kvm->slots_arch_lock);
> + gfn_track = vcalloc(slot->npages, sizeof(*gfn_track));
> + if (gfn_track == NULL)
> + return -ENOMEM;
>
> + slot->arch.gfn_track[KVM_PAGE_TRACK_WRITE] = gfn_track;
> return 0;
> }
>
> @@ -148,7 +118,7 @@ void kvm_slot_page_track_add_page(struct kvm *kvm,
> return;
>
> if (WARN_ON(mode == KVM_PAGE_TRACK_WRITE &&
> - !write_tracking_enabled(kvm)))
> + !kvm_page_track_write_tracking_enabled(kvm)))
> return;
>
> update_gfn_track(slot, gfn, mode, 1);
> @@ -186,7 +156,7 @@ void kvm_slot_page_track_remove_page(struct kvm *kvm,
> return;
>
> if (WARN_ON(mode == KVM_PAGE_TRACK_WRITE &&
> - !write_tracking_enabled(kvm)))
> + !kvm_page_track_write_tracking_enabled(kvm)))
> return;
>
> update_gfn_track(slot, gfn, mode, -1);
> @@ -214,7 +184,8 @@ bool kvm_slot_page_track_is_active(struct kvm_vcpu *vcpu,
> if (!slot)
> return false;
>
> - if (mode == KVM_PAGE_TRACK_WRITE && !write_tracking_enabled(vcpu->kvm))
> + if (mode == KVM_PAGE_TRACK_WRITE &&
> + !kvm_page_track_write_tracking_enabled(vcpu->kvm))
> return false;
>
> index = gfn_to_index(gfn, slot->base_gfn, PG_LEVEL_4K);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index fce4d2eb69e6..b515a3d85a46 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -11516,8 +11516,7 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
> kvm_page_track_free_memslot(slot);
> }
>
> -static int memslot_rmap_alloc(struct kvm_memory_slot *slot,
> - unsigned long npages)
> +int memslot_rmap_alloc(struct kvm_memory_slot *slot, unsigned long npages)
> {
> const int sz = sizeof(*slot->arch.rmap[0]);
> int i;
> @@ -11539,50 +11538,6 @@ static int memslot_rmap_alloc(struct kvm_memory_slot *slot,
> return 0;
> }
>
> -int alloc_all_memslots_rmaps(struct kvm *kvm)
> -{
> - struct kvm_memslots *slots;
> - struct kvm_memory_slot *slot;
> - int r, i;
> -
> - /*
> - * Check if memslots alreday have rmaps early before acquiring
> - * the slots_arch_lock below.
> - */
> - if (kvm_memslots_have_rmaps(kvm))
> - return 0;
> -
> - mutex_lock(&kvm->slots_arch_lock);
> -
> - /*
> - * Read memslots_have_rmaps again, under the slots arch lock,
> - * before allocating the rmaps
> - */
> - if (kvm_memslots_have_rmaps(kvm)) {
> - mutex_unlock(&kvm->slots_arch_lock);
> - return 0;
> - }
> -
> - for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
> - slots = __kvm_memslots(kvm, i);
> - kvm_for_each_memslot(slot, slots) {
> - r = memslot_rmap_alloc(slot, slot->npages);
> - if (r) {
> - mutex_unlock(&kvm->slots_arch_lock);
> - return r;
> - }
> - }
> - }
> -
> - /*
> - * Ensure that memslots_have_rmaps becomes true strictly after
> - * all the rmap pointers are set.
> - */
> - smp_store_release(&kvm->arch.memslots_have_rmaps, true);
> - mutex_unlock(&kvm->slots_arch_lock);
> - return 0;
> -}
> -
> static int kvm_alloc_memslot_metadata(struct kvm *kvm,
> struct kvm_memory_slot *slot,
> unsigned long npages)
