We noticed that kvm_mmu_zap_all() could take hundreds of milliseconds for zapping mmu pages with mmu_lock held.
Although we need to do conditional rescheduling for completely fixing this issue, we can reduce the hold time to some extent by moving free_zapped_mmu_pages() out of the protection. Since invalid_list can be very long, the effect is not negligible. Note: this patch does not treat non-trivial cases. Signed-off-by: Takuya Yoshikawa <[email protected]> --- arch/x86/kvm/mmu.c | 20 +++++++++++++------- 1 files changed, 13 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index dd7b455..7976f55 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2185,7 +2185,6 @@ void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int goal_nr_mmu_pages) kvm_mmu_prepare_zap_page(kvm, page, &invalid_list, NULL); } kvm_mmu_commit_zap_page(kvm, &invalid_list); - free_zapped_mmu_pages(kvm, &invalid_list); goal_nr_mmu_pages = kvm->arch.n_used_mmu_pages; } @@ -2193,6 +2192,8 @@ void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int goal_nr_mmu_pages) kvm->arch.n_max_mmu_pages = goal_nr_mmu_pages; spin_unlock(&kvm->mmu_lock); + + free_zapped_mmu_pages(kvm, &invalid_list); } int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn) @@ -2213,9 +2214,10 @@ int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn) kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list, &npos); } kvm_mmu_commit_zap_page(kvm, &invalid_list); - free_zapped_mmu_pages(kvm, &invalid_list); spin_unlock(&kvm->mmu_lock); + free_zapped_mmu_pages(kvm, &invalid_list); + return r; } EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page); @@ -2934,10 +2936,11 @@ static void mmu_free_roots(struct kvm_vcpu *vcpu) kvm_mmu_prepare_zap_page(vcpu->kvm, sp, &invalid_list, NULL); kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list); - free_zapped_mmu_pages(vcpu->kvm, &invalid_list); } vcpu->arch.mmu.root_hpa = INVALID_PAGE; spin_unlock(&vcpu->kvm->mmu_lock); + + free_zapped_mmu_pages(vcpu->kvm, &invalid_list); return; } for (i = 0; i < 4; ++i) { @@ -2954,9 +2957,10 @@ static void mmu_free_roots(struct kvm_vcpu *vcpu) vcpu->arch.mmu.pae_root[i] = INVALID_PAGE; } kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list); - free_zapped_mmu_pages(vcpu->kvm, &invalid_list); spin_unlock(&vcpu->kvm->mmu_lock); + + free_zapped_mmu_pages(vcpu->kvm, &invalid_list); vcpu->arch.mmu.root_hpa = INVALID_PAGE; } @@ -4054,10 +4058,11 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, mmu_pte_write_flush_tlb(vcpu, zap_page, remote_flush, local_flush); kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list); - free_zapped_mmu_pages(vcpu->kvm, &invalid_list); kvm_mmu_audit(vcpu, AUDIT_POST_PTE_WRITE); spin_unlock(&vcpu->kvm->mmu_lock); + + free_zapped_mmu_pages(vcpu->kvm, &invalid_list); } int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva) @@ -4254,9 +4259,10 @@ restart: goto restart; kvm_mmu_commit_zap_page(kvm, &invalid_list); - free_zapped_mmu_pages(kvm, &invalid_list); spin_unlock(&kvm->mmu_lock); + + free_zapped_mmu_pages(kvm, &invalid_list); } static void kvm_mmu_remove_some_alloc_mmu_pages(struct kvm *kvm, @@ -4308,10 +4314,10 @@ static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc) kvm_mmu_remove_some_alloc_mmu_pages(kvm, &invalid_list); kvm_mmu_commit_zap_page(kvm, &invalid_list); - free_zapped_mmu_pages(kvm, &invalid_list); spin_unlock(&kvm->mmu_lock); srcu_read_unlock(&kvm->srcu, idx); + free_zapped_mmu_pages(kvm, &invalid_list); list_move_tail(&kvm->vm_list, &vm_list); break; -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
