Decompose kvm_mmu_get_page() into separate helper functions to increase readability and prepare for allocating shadow pages without a vcpu pointer. Specifically, pull the guts of kvm_mmu_get_page() into 3 helper functions: __kvm_mmu_find_shadow_page() - Walks the page hash checking for any existing mmu pages that match the given gfn and role. Does not attempt to synchronize the page if it is unsync. kvm_mmu_find_shadow_page() - Wraps __kvm_mmu_find_shadow_page() and handles syncing if necessary. kvm_mmu_new_shadow_page() Allocates and initializes an entirely new kvm_mmu_page. This currently requries a vcpu pointer for allocation and looking up the memslot but that will be removed in a future commit. Note, kvm_mmu_new_shadow_page() is temporary and will be removed in a subsequent commit. The name uses "new" rather than the more typical "alloc" to avoid clashing with the existing kvm_mmu_alloc_page(). No functional change intended. Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx> --- arch/x86/kvm/mmu/mmu.c | 132 ++++++++++++++++++++++++--------- arch/x86/kvm/mmu/paging_tmpl.h | 5 +- arch/x86/kvm/mmu/spte.c | 5 +- 3 files changed, 101 insertions(+), 41 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 23c2004c6435..80dbfe07c87b 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2027,16 +2027,25 @@ static void clear_sp_write_flooding_count(u64 *spte) __clear_sp_write_flooding_count(sptep_to_sp(spte)); } -static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, gfn_t gfn, - union kvm_mmu_page_role role) +/* + * Searches for an existing SP for the given gfn and role. Makes no attempt to + * sync the SP if it is marked unsync. + * + * If creating an upper-level page table, zaps unsynced pages for the same + * gfn and adds them to the invalid_list. It's the callers responsibility + * to call kvm_mmu_commit_zap_page() on invalid_list. + */ +static struct kvm_mmu_page *__kvm_mmu_find_shadow_page(struct kvm *kvm, + gfn_t gfn, + union kvm_mmu_page_role role, + struct list_head *invalid_list) { struct hlist_head *sp_list; struct kvm_mmu_page *sp; int collisions = 0; - LIST_HEAD(invalid_list); - sp_list = &vcpu->kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)]; - for_each_valid_sp(vcpu->kvm, sp, sp_list) { + sp_list = &kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)]; + for_each_valid_sp(kvm, sp, sp_list) { if (sp->gfn != gfn) { collisions++; continue; @@ -2053,60 +2062,109 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, gfn_t gfn, * upper-level page will be write-protected. */ if (role.level > PG_LEVEL_4K && sp->unsync) - kvm_mmu_prepare_zap_page(vcpu->kvm, sp, - &invalid_list); + kvm_mmu_prepare_zap_page(kvm, sp, invalid_list); + continue; } - /* unsync and write-flooding only apply to indirect SPs. */ - if (sp->role.direct) - goto trace_get_page; + /* Write-flooding is only tracked for indirect SPs. */ + if (!sp->role.direct) + __clear_sp_write_flooding_count(sp); - if (sp->unsync) { - /* - * The page is good, but is stale. kvm_sync_page does - * get the latest guest state, but (unlike mmu_unsync_children) - * it doesn't write-protect the page or mark it synchronized! - * This way the validity of the mapping is ensured, but the - * overhead of write protection is not incurred until the - * guest invalidates the TLB mapping. This allows multiple - * SPs for a single gfn to be unsync. - * - * If the sync fails, the page is zapped. If so, break - * in order to rebuild it. - */ - if (!kvm_sync_page(vcpu, sp, &invalid_list)) - break; + goto out; + } - WARN_ON(!list_empty(&invalid_list)); - kvm_flush_remote_tlbs(vcpu->kvm); - } + sp = NULL; - __clear_sp_write_flooding_count(sp); +out: + if (collisions > kvm->stat.max_mmu_page_hash_collisions) + kvm->stat.max_mmu_page_hash_collisions = collisions; + + return sp; +} -trace_get_page: - trace_kvm_mmu_get_page(sp, false); +/* + * Looks up an existing SP for the given gfn and role if one exists. The + * return SP is guaranteed to be synced. + */ +static struct kvm_mmu_page *kvm_mmu_find_shadow_page(struct kvm_vcpu *vcpu, + gfn_t gfn, + union kvm_mmu_page_role role) +{ + struct kvm_mmu_page *sp; + LIST_HEAD(invalid_list); + + sp = __kvm_mmu_find_shadow_page(vcpu->kvm, gfn, role, &invalid_list); + if (!sp) goto out; + + if (sp->unsync) { + /* + * The page is good, but is stale. kvm_sync_page does + * get the latest guest state, but (unlike mmu_unsync_children) + * it doesn't write-protect the page or mark it synchronized! + * This way the validity of the mapping is ensured, but the + * overhead of write protection is not incurred until the + * guest invalidates the TLB mapping. This allows multiple + * SPs for a single gfn to be unsync. + * + * If the sync fails, the page is zapped and added to the + * invalid_list. + */ + if (!kvm_sync_page(vcpu, sp, &invalid_list)) { + sp = NULL; + goto out; + } + + WARN_ON(!list_empty(&invalid_list)); + kvm_flush_remote_tlbs(vcpu->kvm); } +out: + kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list); + return sp; +} + +static struct kvm_mmu_page *kvm_mmu_new_shadow_page(struct kvm_vcpu *vcpu, + gfn_t gfn, + union kvm_mmu_page_role role) +{ + struct kvm_mmu_page *sp; + struct hlist_head *sp_list; + ++vcpu->kvm->stat.mmu_cache_miss; sp = kvm_mmu_alloc_page(vcpu, role.direct); - sp->gfn = gfn; sp->role = role; + + sp_list = &vcpu->kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)]; hlist_add_head(&sp->hash_link, sp_list); + if (!role.direct) { account_shadowed(vcpu->kvm, sp); if (role.level == PG_LEVEL_4K && kvm_vcpu_write_protect_gfn(vcpu, gfn)) kvm_flush_remote_tlbs_with_address(vcpu->kvm, gfn, 1); } - trace_kvm_mmu_get_page(sp, true); -out: - kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list); - if (collisions > vcpu->kvm->stat.max_mmu_page_hash_collisions) - vcpu->kvm->stat.max_mmu_page_hash_collisions = collisions; + return sp; +} + +static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, gfn_t gfn, + union kvm_mmu_page_role role) +{ + struct kvm_mmu_page *sp; + bool created = false; + + sp = kvm_mmu_find_shadow_page(vcpu, gfn, role); + if (sp) + goto out; + + created = true; + sp = kvm_mmu_new_shadow_page(vcpu, gfn, role); + +out: + trace_kvm_mmu_get_page(sp, created); return sp; } diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h index c3909a07e938..55cac59b9c9b 100644 --- a/arch/x86/kvm/mmu/paging_tmpl.h +++ b/arch/x86/kvm/mmu/paging_tmpl.h @@ -692,8 +692,9 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, * the gpte is changed from non-present to present. * Otherwise, the guest may use the wrong mapping. * - * For PG_LEVEL_4K, kvm_mmu_get_page() has already - * synchronized it transiently via kvm_sync_page(). + * For PG_LEVEL_4K, kvm_mmu_get_existing_sp() has + * already synchronized it transiently via + * kvm_sync_page(). * * For higher level pagetable, we synchronize it via * the slower mmu_sync_children(). If it needs to diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c index 4739b53c9734..d10189d9c877 100644 --- a/arch/x86/kvm/mmu/spte.c +++ b/arch/x86/kvm/mmu/spte.c @@ -150,8 +150,9 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, /* * Optimization: for pte sync, if spte was writable the hash * lookup is unnecessary (and expensive). Write protection - * is responsibility of kvm_mmu_get_page / kvm_mmu_sync_roots. - * Same reasoning can be applied to dirty page accounting. + * is responsibility of kvm_mmu_create_sp() and + * kvm_mmu_sync_roots(). Same reasoning can be applied to dirty + * page accounting. */ if (is_writable_pte(old_spte)) goto out; -- 2.35.1.723.g4982287a31-goog