Revert "KVM: MMU: fast invalidate all pages"

Remove x86 KVM's fast invalidate mechanism, i.e. revert all patches
from the original series[1], now that all users of the fast invalidate
mechanism are gone.

This reverts commit 5304b8d3.

[1] https://lkml.kernel.org/r/1369960590-14138-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com

Cc: Xiao Guangrong <guangrong.xiao@gmail.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -334,7 +334,6 @@ struct kvm_mmu_page {
 	int root_count;          /* Currently serving as active root */
 	unsigned int unsync_children;
 	struct kvm_rmap_head parent_ptes; /* rmap pointers to parent sptes */
-	unsigned long mmu_valid_gen;
 	DECLARE_BITMAP(unsync_child_bitmap, 512);
 
 #ifdef CONFIG_X86_32
@@ -845,7 +844,6 @@ struct kvm_arch {
 	unsigned int n_requested_mmu_pages;
 	unsigned int n_max_mmu_pages;
 	unsigned int indirect_shadow_pages;
-	unsigned long mmu_valid_gen;
 	struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES];
 	/*
 	 * Hash table of struct kvm_mmu_page.

arch/x86/kvm/mmu.c

@@ -2060,12 +2060,6 @@ static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu, int direct
 	if (!direct)
 		sp->gfns = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache);
 	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
-
-	/*
-	 * The active_mmu_pages list is the FIFO list, do not move the
-	 * page until it is zapped. kvm_zap_obsolete_pages depends on
-	 * this feature. See the comments in kvm_zap_obsolete_pages().
-	 */
 	list_add(&sp->link, &vcpu->kvm->arch.active_mmu_pages);
 	kvm_mod_used_mmu_pages(vcpu->kvm, +1);
 	return sp;
@@ -2214,7 +2208,7 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
 #define for_each_valid_sp(_kvm, _sp, _gfn)				\
 	hlist_for_each_entry(_sp,					\
 	  &(_kvm)->arch.mmu_page_hash[kvm_page_table_hashfn(_gfn)], hash_link) \
-		if (is_obsolete_sp((_kvm), (_sp)) || (_sp)->role.invalid) {    \
+		if ((_sp)->role.invalid) {    \
 		} else
 
 #define for_each_gfn_indirect_valid_sp(_kvm, _sp, _gfn)			\
@@ -2266,11 +2260,6 @@ static void kvm_mmu_audit(struct kvm_vcpu *vcpu, int point) { }
 static void mmu_audit_disable(void) { }
 #endif
 
-static bool is_obsolete_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
-{
-	return unlikely(sp->mmu_valid_gen != kvm->arch.mmu_valid_gen);
-}
-
 static bool kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
 			 struct list_head *invalid_list)
 {
@@ -2495,7 +2484,6 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
 		if (level > PT_PAGE_TABLE_LEVEL && need_sync)
 			flush |= kvm_sync_pages(vcpu, gfn, &invalid_list);
 	}
-	sp->mmu_valid_gen = vcpu->kvm->arch.mmu_valid_gen;
 	clear_page(sp->spt);
 	trace_kvm_mmu_get_page(sp, true);
 
@@ -4206,14 +4194,6 @@ static bool fast_cr3_switch(struct kvm_vcpu *vcpu, gpa_t new_cr3,
 			return false;
 
 		if (cached_root_available(vcpu, new_cr3, new_role)) {
-			/*
-			 * It is possible that the cached previous root page is
-			 * obsolete because of a change in the MMU
-			 * generation number. However, that is accompanied by
-			 * KVM_REQ_MMU_RELOAD, which will free the root that we
-			 * have set here and allocate a new one.
-			 */
-
 			kvm_make_request(KVM_REQ_LOAD_CR3, vcpu);
 			if (!skip_tlb_flush) {
 				kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
@@ -5865,82 +5845,6 @@ void kvm_mmu_zap_all(struct kvm *kvm)
 	spin_unlock(&kvm->mmu_lock);
 }
 
-static void kvm_zap_obsolete_pages(struct kvm *kvm)
-{
-	struct kvm_mmu_page *sp, *node;
-	LIST_HEAD(invalid_list);
-
-restart:
-	list_for_each_entry_safe_reverse(sp, node,
-	      &kvm->arch.active_mmu_pages, link) {
-		/*
-		 * No obsolete page exists before new created page since
-		 * active_mmu_pages is the FIFO list.
-		 */
-		if (!is_obsolete_sp(kvm, sp))
-			break;
-
-		/*
-		 * Do not repeatedly zap a root page to avoid unnecessary
-		 * KVM_REQ_MMU_RELOAD, otherwise we may not be able to
-		 * progress:
-		 *    vcpu 0                        vcpu 1
-		 *                         call vcpu_enter_guest():
-		 *                            1): handle KVM_REQ_MMU_RELOAD
-		 *                                and require mmu-lock to
-		 *                                load mmu
-		 * repeat:
-		 *    1): zap root page and
-		 *        send KVM_REQ_MMU_RELOAD
-		 *
-		 *    2): if (cond_resched_lock(mmu-lock))
-		 *
-		 *                            2): hold mmu-lock and load mmu
-		 *
-		 *                            3): see KVM_REQ_MMU_RELOAD bit
-		 *                                on vcpu->requests is set
-		 *                                then return 1 to call
-		 *                                vcpu_enter_guest() again.
-		 *            goto repeat;
-		 *
-		 * Since we are reversely walking the list and the invalid
-		 * list will be moved to the head, skip the invalid page
-		 * can help us to avoid the infinity list walking.
-		 */
-		if (sp->role.invalid)
-			continue;
-
-		if (need_resched() || spin_needbreak(&kvm->mmu_lock)) {
-			kvm_mmu_commit_zap_page(kvm, &invalid_list);
-			cond_resched_lock(&kvm->mmu_lock);
-			goto restart;
-		}
-
-		if (kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list))
-			goto restart;
-	}
-
-	kvm_mmu_commit_zap_page(kvm, &invalid_list);
-}
-
-/*
- * Fast invalidate all shadow pages and use lock-break technique
- * to zap obsolete pages.
- *
- * It's required when memslot is being deleted or VM is being
- * destroyed, in these cases, we should ensure that KVM MMU does
- * not use any resource of the being-deleted slot or all slots
- * after calling the function.
- */
-void kvm_mmu_invalidate_zap_all_pages(struct kvm *kvm)
-{
-	spin_lock(&kvm->mmu_lock);
-	kvm->arch.mmu_valid_gen++;
-
-	kvm_zap_obsolete_pages(kvm);
-	spin_unlock(&kvm->mmu_lock);
-}
-
 static void kvm_mmu_zap_mmio_sptes(struct kvm *kvm)
 {
 	struct kvm_mmu_page *sp, *node;

arch/x86/kvm/mmu.h

@@ -203,7 +203,6 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
 	return -(u32)fault & errcode;
 }
 
-void kvm_mmu_invalidate_zap_all_pages(struct kvm *kvm);
 void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end);
 
 void kvm_mmu_gfn_disallow_lpage(struct kvm_memory_slot *slot, gfn_t gfn);