| Message ID | 20210202185734.1680553-26-bgardon@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Allow parallel MMU operations with TDP MMU | expand |
On 02/02/21 19:57, Ben Gardon wrote: > @@ -1485,7 +1489,9 @@ void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm, > struct kvm_mmu_page *root; > int root_as_id; > > - for_each_tdp_mmu_root_yield_safe(kvm, root, false) { > + read_lock(&kvm->mmu_lock); > + > + for_each_tdp_mmu_root_yield_safe(kvm, root, true) { > root_as_id = kvm_mmu_page_as_id(root); > if (root_as_id != slot->as_id) > continue; > @@ -1493,6 +1499,8 @@ void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm, > zap_collapsible_spte_range(kvm, root, slot->base_gfn, > slot->base_gfn + slot->npages); > } > + > + read_unlock(&kvm->mmu_lock); > } I'd prefer the functions to be consistent about who takes the lock, either mmu.c or tdp_mmu.c. Since everywhere else you're doing it in mmu.c, that would be: diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 0554d9c5c5d4..386ee4b703d9 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -5567,10 +5567,13 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm, write_lock(&kvm->mmu_lock); slot_handle_leaf(kvm, (struct kvm_memory_slot *)memslot, kvm_mmu_zap_collapsible_spte, true); + write_unlock(&kvm->mmu_lock); - if (kvm->arch.tdp_mmu_enabled) + if (kvm->arch.tdp_mmu_enabled) { + read_lock(&kvm->mmu_lock); kvm_tdp_mmu_zap_collapsible_sptes(kvm, memslot); - write_unlock(&kvm->mmu_lock); + read_unlock(&kvm->mmu_lock); + } } void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm, and just lockdep_assert_held_read here. > - tdp_mmu_set_spte(kvm, &iter, 0); > - > - spte_set = true; Is it correct to remove this assignment? Paolo
On Wed, Feb 3, 2021 at 3:34 AM Paolo Bonzini <pbonzini@redhat.com> wrote: > > On 02/02/21 19:57, Ben Gardon wrote: > > @@ -1485,7 +1489,9 @@ void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm, > > struct kvm_mmu_page *root; > > int root_as_id; > > > > - for_each_tdp_mmu_root_yield_safe(kvm, root, false) { > > + read_lock(&kvm->mmu_lock); > > + > > + for_each_tdp_mmu_root_yield_safe(kvm, root, true) { > > root_as_id = kvm_mmu_page_as_id(root); > > if (root_as_id != slot->as_id) > > continue; > > @@ -1493,6 +1499,8 @@ void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm, > > zap_collapsible_spte_range(kvm, root, slot->base_gfn, > > slot->base_gfn + slot->npages); > > } > > + > > + read_unlock(&kvm->mmu_lock); > > } > > > I'd prefer the functions to be consistent about who takes the lock, > either mmu.c or tdp_mmu.c. Since everywhere else you're doing it in > mmu.c, that would be: > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 0554d9c5c5d4..386ee4b703d9 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -5567,10 +5567,13 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm, > write_lock(&kvm->mmu_lock); > slot_handle_leaf(kvm, (struct kvm_memory_slot *)memslot, > kvm_mmu_zap_collapsible_spte, true); > + write_unlock(&kvm->mmu_lock); > > - if (kvm->arch.tdp_mmu_enabled) > + if (kvm->arch.tdp_mmu_enabled) { > + read_lock(&kvm->mmu_lock); > kvm_tdp_mmu_zap_collapsible_sptes(kvm, memslot); > - write_unlock(&kvm->mmu_lock); > + read_unlock(&kvm->mmu_lock); > + } > } > > void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm, > > and just lockdep_assert_held_read here. That makes sense to me, I agree keeping it consistent is probably a good idea. > > > - tdp_mmu_set_spte(kvm, &iter, 0); > > - > > - spte_set = true; > > Is it correct to remove this assignment? No, it was not correct to remove it. Thank you for catching that. > > Paolo >
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 254ff87d2a61..e3cf868be6bd 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -5517,8 +5517,7 @@ void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end) start, end - 1, true); } } - - kvm_mmu_unlock(kvm); + write_unlock(&kvm->mmu_lock); if (kvm->arch.tdp_mmu_enabled) { read_lock(&kvm->mmu_lock); @@ -5611,10 +5610,10 @@ void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm, write_lock(&kvm->mmu_lock); slot_handle_leaf(kvm, (struct kvm_memory_slot *)memslot, kvm_mmu_zap_collapsible_spte, true); + write_unlock(&kvm->mmu_lock); if (kvm->arch.tdp_mmu_enabled) kvm_tdp_mmu_zap_collapsible_sptes(kvm, memslot); - write_unlock(&kvm->mmu_lock); } void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm, diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index de26762433ea..cfe66b8d39fa 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1451,10 +1451,9 @@ static void zap_collapsible_spte_range(struct kvm *kvm, rcu_read_lock(); tdp_root_for_each_pte(iter, root, start, end) { - if (tdp_mmu_iter_cond_resched(kvm, &iter, false, false)) { - spte_set = false; +retry: + if (tdp_mmu_iter_cond_resched(kvm, &iter, false, true)) continue; - } if (!is_shadow_present_pte(iter.old_spte) || !is_last_spte(iter.old_spte, iter.level)) @@ -1465,9 +1464,14 @@ static void zap_collapsible_spte_range(struct kvm *kvm, !PageTransCompoundMap(pfn_to_page(pfn))) continue; - tdp_mmu_set_spte(kvm, &iter, 0); - - spte_set = true; + if (!tdp_mmu_zap_spte_atomic(kvm, &iter)) { + /* + * The iter must explicitly re-read the SPTE because + * the atomic cmpxchg failed. + */ + iter.old_spte = READ_ONCE(*rcu_dereference(iter.sptep)); + goto retry; + } } rcu_read_unlock(); @@ -1485,7 +1489,9 @@ void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm, struct kvm_mmu_page *root; int root_as_id; - for_each_tdp_mmu_root_yield_safe(kvm, root, false) { + read_lock(&kvm->mmu_lock); + + for_each_tdp_mmu_root_yield_safe(kvm, root, true) { root_as_id = kvm_mmu_page_as_id(root); if (root_as_id != slot->as_id) continue; @@ -1493,6 +1499,8 @@ void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm, zap_collapsible_spte_range(kvm, root, slot->base_gfn, slot->base_gfn + slot->npages); } + + read_unlock(&kvm->mmu_lock); } /*
To speed the process of disabling dirty logging, change the TDP MMU function which zaps collapsible SPTEs to run under the MMU read lock. Signed-off-by: Ben Gardon <bgardon@google.com> --- arch/x86/kvm/mmu/mmu.c | 5 ++--- arch/x86/kvm/mmu/tdp_mmu.c | 22 +++++++++++++++------- 2 files changed, 17 insertions(+), 10 deletions(-)