!1625 Fix host zero page refcount overflow caused by kvm

Merge Pull Request from: @ci-robot 
 
PR sync from: Lei Chen <lei.chen@smartx.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/YBB4FWVDSAGSXOH4VTUKE6MMDOJWYADW/ 
v2:
1. using full commit id instead of abbrevation
2. fix wrong mainline tag

Sean Christopherson (1):
  KVM: Don't set Accessed/Dirty bits for ZERO_PAGE

Zhuang Yanying (1):
  KVM: fix overflow of zero page refcount with ksm running


-- 
2.34.1
 
https://gitee.com/openeuler/kernel/issues/I7PQPE?from=project-issue 
 
Link:https://gitee.com/openeuler/kernel/pulls/1625 

Reviewed-by: Kevin Zhu <zhukeqian1@huawei.com> 
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com> 

virt/kvm/kvm_main.c

@@ -170,6 +170,7 @@ bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
 	 */
 	if (pfn_valid(pfn))
 		return PageReserved(pfn_to_page(pfn)) &&
+		       !is_zero_pfn(pfn) &&
 		       !kvm_is_zone_device_pfn(pfn);
 
 	return true;
@@ -1844,20 +1845,28 @@ void kvm_release_pfn_dirty(kvm_pfn_t pfn)
 }
 EXPORT_SYMBOL_GPL(kvm_release_pfn_dirty);
 
-void kvm_set_pfn_dirty(kvm_pfn_t pfn)
+static bool kvm_is_ad_tracked_pfn(kvm_pfn_t pfn)
 {
-	if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn)) {
-		struct page *page = pfn_to_page(pfn);
+	if (!pfn_valid(pfn))
+		return false;
 
-		if (!PageReserved(page))
-			SetPageDirty(page);
-	}
+	/*
+	 * Per page-flags.h, pages tagged PG_reserved "should in general not be
+	 * touched (e.g. set dirty) except by its owner".
+	 */
+	return !PageReserved(pfn_to_page(pfn));
+}
+
+void kvm_set_pfn_dirty(kvm_pfn_t pfn)
+{
+	if (kvm_is_ad_tracked_pfn(pfn))
+		SetPageDirty(pfn_to_page(pfn));
 }
 EXPORT_SYMBOL_GPL(kvm_set_pfn_dirty);
 
 void kvm_set_pfn_accessed(kvm_pfn_t pfn)
 {
-	if (!kvm_is_reserved_pfn(pfn) && !kvm_is_zone_device_pfn(pfn))
+	if (kvm_is_ad_tracked_pfn(pfn))
 		mark_page_accessed(pfn_to_page(pfn));
 }
 EXPORT_SYMBOL_GPL(kvm_set_pfn_accessed);