On Thu, Sep 29, 2022 at 09:52:06AM -0700, Isaku Yamahata wrote: > On Thu, Sep 15, 2022 at 10:29:11PM +0800, > Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> wrote: > > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > > index 08abad4f3e6f..a0f198cede3d 100644 > > --- a/arch/x86/kvm/mmu/mmu.c > > +++ b/arch/x86/kvm/mmu/mmu.c > ... > > @@ -6894,3 +6899,115 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm) > > if (kvm->arch.nx_lpage_recovery_thread) > > kthread_stop(kvm->arch.nx_lpage_recovery_thread); > > } > > + > > +static bool mem_attr_is_mixed(struct kvm *kvm, unsigned int attr, > > + gfn_t start, gfn_t end) > > +{ > > + XA_STATE(xas, &kvm->mem_attr_array, start); > > + gfn_t gfn = start; > > + void *entry; > > + bool shared, private; > > + bool mixed = false; > > + > > + if (attr == KVM_MEM_ATTR_SHARED) { > > + shared = true; > > + private = false; > > + } else { > > + shared = false; > > + private = true; > > + } > > We don't have to care the target is shared or private. We need to check > only same or not. There is optimization chance if we know what we are going to set. we can return 'mixed = true' earlier when we find the first reverse attr, e.g. it's unnecessarily to check all the child page attr in one largepage to give a conclusion. After a further look, the code can be refined as below: --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -7255,17 +7255,9 @@ static bool mem_attr_is_mixed(struct kvm *kvm, unsigned int attr, XA_STATE(xas, &kvm->mem_attr_array, start); gfn_t gfn = start; void *entry; - bool shared, private; + bool shared = attr == KVM_MEM_ATTR_SHARED; bool mixed = false; - if (attr == KVM_MEM_ATTR_SHARED) { - shared = true; - private = false; - } else { - shared = false; - private = true; - } - rcu_read_lock(); entry = xas_load(&xas); while (gfn < end) { @@ -7274,12 +7266,7 @@ static bool mem_attr_is_mixed(struct kvm *kvm, unsigned int attr, KVM_BUG_ON(gfn != xas.xa_index, kvm); - if (entry) - private = true; - else - shared = true; - - if (private && shared) { + if ((entry && !shared) || (!entry && shared)) { mixed = true; goto out; } @@ -7320,8 +7307,7 @@ static void update_mem_lpage_info(struct kvm *kvm, * we know they are not mixed. */ update_mixed(lpage_info_slot(lpage_start, slot, level), - mem_attr_is_mixed(kvm, attr, lpage_start, - lpage_start + pages)); + mem_attr_is_mixed(kvm, attr, lpage_start, start)); if (lpage_start == lpage_end) return; @@ -7330,7 +7316,7 @@ static void update_mem_lpage_info(struct kvm *kvm, update_mixed(lpage_info_slot(gfn, slot, level), false); update_mixed(lpage_info_slot(lpage_end, slot, level), - mem_attr_is_mixed(kvm, attr, lpage_end, + mem_attr_is_mixed(kvm, attr, end, lpage_end + pages)); } } > > > + > > + rcu_read_lock(); > > + entry = xas_load(&xas); > > + while (gfn < end) { > > + if (xas_retry(&xas, entry)) > > + continue; > > + > > + KVM_BUG_ON(gfn != xas.xa_index, kvm); > > + > > + if (entry) > > + private = true; > > + else > > + shared = true; > > + > > + if (private && shared) { > > + mixed = true; > > + goto out; > > + } > > + > > + entry = xas_next(&xas); > > + gfn++; > > + } > > +out: > > + rcu_read_unlock(); > > + return mixed; > > +} > > + > > +static inline void update_mixed(struct kvm_lpage_info *linfo, bool mixed) > > +{ > > + if (mixed) > > + linfo->disallow_lpage |= KVM_LPAGE_PRIVATE_SHARED_MIXED; > > + else > > + linfo->disallow_lpage &= ~KVM_LPAGE_PRIVATE_SHARED_MIXED; > > +} > > + > > +static void update_mem_lpage_info(struct kvm *kvm, > > + struct kvm_memory_slot *slot, > > + unsigned int attr, > > + gfn_t start, gfn_t end) > > +{ > > + unsigned long lpage_start, lpage_end; > > + unsigned long gfn, pages, mask; > > + int level; > > + > > + for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) { > > + pages = KVM_PAGES_PER_HPAGE(level); > > + mask = ~(pages - 1); > > + lpage_start = start & mask; > > + lpage_end = (end - 1) & mask; > > + > > + /* > > + * We only need to scan the head and tail page, for middle pages > > + * we know they are not mixed. > > + */ > > + update_mixed(lpage_info_slot(lpage_start, slot, level), > > + mem_attr_is_mixed(kvm, attr, lpage_start, > > + lpage_start + pages)); > > + > > + if (lpage_start == lpage_end) > > + return; > > + > > + for (gfn = lpage_start + pages; gfn < lpage_end; gfn += pages) > > + update_mixed(lpage_info_slot(gfn, slot, level), false); > > > For >2M case, we don't have to check all entry. just check lower level case. Sounds good, we can reduce some scanning. Thanks, Chao > > > + > > + update_mixed(lpage_info_slot(lpage_end, slot, level), > > + mem_attr_is_mixed(kvm, attr, lpage_end, > > + lpage_end + pages)); > > + } > > +} > > + > > +void kvm_arch_update_mem_attr(struct kvm *kvm, unsigned int attr, > > + gfn_t start, gfn_t end) > > +{ > > + struct kvm_memory_slot *slot; > > + struct kvm_memslots *slots; > > + struct kvm_memslot_iter iter; > > + int i; > > + > > + WARN_ONCE(!(attr & (KVM_MEM_ATTR_PRIVATE | KVM_MEM_ATTR_SHARED)), > > + "Unsupported mem attribute.\n"); > > + > > + for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) { > > + slots = __kvm_memslots(kvm, i); > > + > > + kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) { > > + slot = iter.slot; > > + start = max(start, slot->base_gfn); > > + end = min(end, slot->base_gfn + slot->npages); > > + if (WARN_ON_ONCE(start >= end)) > > + continue; > > + > > + update_mem_lpage_info(kvm, slot, attr, start, end); > > + } > > + } > > +} > > > Here is my updated version. > > bool kvm_mem_attr_is_mixed(struct kvm_memory_slot *slot, gfn_t gfn, int level) > { > gfn_t pages = KVM_PAGES_PER_HPAGE(level); > gfn_t mask = ~(pages - 1); > struct kvm_lpage_info *linfo = lpage_info_slot(gfn & mask, slot, level); > > WARN_ON_ONCE(level == PG_LEVEL_4K); > return linfo->disallow_lpage & KVM_LPAGE_PRIVATE_SHARED_MIXED; > } > > #ifdef CONFIG_HAVE_KVM_PRIVATE_MEM_ATTR > static void update_mixed(struct kvm_lpage_info *linfo, bool mixed) > { > if (mixed) > linfo->disallow_lpage |= KVM_LPAGE_PRIVATE_SHARED_MIXED; > else > linfo->disallow_lpage &= ~KVM_LPAGE_PRIVATE_SHARED_MIXED; > } > > static bool __mem_attr_is_mixed(struct kvm *kvm, gfn_t start, gfn_t end) > { > XA_STATE(xas, &kvm->mem_attr_array, start); > bool mixed = false; > gfn_t gfn = start; > void *s_entry; > void *entry; > > rcu_read_lock(); > s_entry = xas_load(&xas); > entry = s_entry; > while (gfn < end) { > if (xas_retry(&xas, entry)) > continue; > > KVM_BUG_ON(gfn != xas.xa_index, kvm); > > entry = xas_next(&xas); > if (entry != s_entry) { > mixed = true; > break; > } > gfn++; > } > rcu_read_unlock(); > return mixed; > } > > static bool mem_attr_is_mixed(struct kvm *kvm, > struct kvm_memory_slot *slot, int level, > gfn_t start, gfn_t end) > { > struct kvm_lpage_info *child_linfo; > unsigned long child_pages; > bool mixed = false; > unsigned long gfn; > void *entry; > > if (WARN_ON_ONCE(level == PG_LEVEL_4K)) > return false; > > if (level == PG_LEVEL_2M) > return __mem_attr_is_mixed(kvm, start, end); > > /* This assumes that level - 1 is already updated. */ > rcu_read_lock(); > child_pages = KVM_PAGES_PER_HPAGE(level - 1); > entry = xa_load(&kvm->mem_attr_array, start); > for (gfn = start; gfn < end; gfn += child_pages) { > child_linfo = lpage_info_slot(gfn, slot, level - 1); > if (child_linfo->disallow_lpage & KVM_LPAGE_PRIVATE_SHARED_MIXED) { > mixed = true; > break; > } > if (xa_load(&kvm->mem_attr_array, gfn) != entry) { > mixed = true; > break; > } > } > rcu_read_unlock(); > return mixed; > } > > static void update_mem_lpage_info(struct kvm *kvm, > struct kvm_memory_slot *slot, > unsigned int attr, > gfn_t start, gfn_t end) > { > unsigned long lpage_start, lpage_end; > unsigned long gfn, pages, mask; > int level; > > for (level = PG_LEVEL_2M; level <= KVM_MAX_HUGEPAGE_LEVEL; level++) { > pages = KVM_PAGES_PER_HPAGE(level); > mask = ~(pages - 1); > lpage_start = start & mask; > lpage_end = (end - 1) & mask; > > /* > * We only need to scan the head and tail page, for middle pages > * we know they are not mixed. > */ > update_mixed(lpage_info_slot(lpage_start, slot, level), > mem_attr_is_mixed(kvm, slot, level, > lpage_start, lpage_start + pages)); > > if (lpage_start == lpage_end) > return; > > for (gfn = lpage_start + pages; gfn < lpage_end; gfn += pages) > update_mixed(lpage_info_slot(gfn, slot, level), false); > > update_mixed(lpage_info_slot(lpage_end, slot, level), > mem_attr_is_mixed(kvm, slot, level, > lpage_end, lpage_end + pages)); > } > } > > void kvm_arch_update_mem_attr(struct kvm *kvm, unsigned int attr, > gfn_t start, gfn_t end) > { > struct kvm_memory_slot *slot; > struct kvm_memslots *slots; > struct kvm_memslot_iter iter; > int idx; > int i; > > WARN_ONCE(!(attr & (KVM_MEM_ATTR_PRIVATE | KVM_MEM_ATTR_SHARED)), > "Unsupported mem attribute.\n"); > > idx = srcu_read_lock(&kvm->srcu); > for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) { > slots = __kvm_memslots(kvm, i); > > kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) { > slot = iter.slot; > start = max(start, slot->base_gfn); > end = min(end, slot->base_gfn + slot->npages); > if (WARN_ON_ONCE(start >= end)) > continue; > > update_mem_lpage_info(kvm, slot, attr, start, end); > } > } > srcu_read_unlock(&kvm->srcu, idx); > } > #endif > > > -- > Isaku Yamahata <isaku.yamahata@xxxxxxxxx>