[patch 4/4] KVM: MMU: pinned sps are not candidates for deletion.

[mtosatti@redhat.com]

[-- Attachment #1: mmu-pinned-spte-skip --]
[-- Type: text/plain, Size: 1732 bytes --]

Skip pinned shadow pages when selecting pages to zap.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

---
 arch/x86/kvm/mmu.c |   26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

Index: kvm.pinned-sptes/arch/x86/kvm/mmu.c
===================================================================
--- kvm.pinned-sptes.orig/arch/x86/kvm/mmu.c	2014-07-09 12:09:26.433674438 -0300
+++ kvm.pinned-sptes/arch/x86/kvm/mmu.c	2014-07-09 12:09:27.164672860 -0300
@@ -2267,16 +2267,24 @@
 static bool prepare_zap_oldest_mmu_page(struct kvm *kvm,
 					struct list_head *invalid_list)
 {
-	struct kvm_mmu_page *sp;
-
-	if (list_empty(&kvm->arch.active_mmu_pages))
-		return false;
+	struct kvm_mmu_page *sp, *nsp;
+	LIST_HEAD(pinned_list);
 
-	sp = list_entry(kvm->arch.active_mmu_pages.prev,
-			struct kvm_mmu_page, link);
-	kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);
+	list_for_each_entry_safe_reverse(sp, nsp,
+					 &kvm->arch.active_mmu_pages, link) {
+		if (sp->pinned) {
+			list_move(&sp->link, &pinned_list);
+			continue;
+		}
+		if (!list_empty(&pinned_list))
+			list_move(&pinned_list, &kvm->arch.active_mmu_pages);
+		kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);
+		return true;
+	}
 
-	return true;
+	if (!list_empty(&pinned_list))
+		list_move(&pinned_list, &kvm->arch.active_mmu_pages);
+	return false;
 }
 
 /*
@@ -4679,6 +4687,8 @@
 	 * Notify all vcpus to reload its shadow page table
 	 * and flush TLB. Then all vcpus will switch to new
 	 * shadow page table with the new mmu_valid_gen.
+	 * MMU reload request also forces fault of
+	 * sptes for pinned ranges.
 	 *
 	 * Note: we should do this under the protection of
 	 * mmu-lock, otherwise, vcpu would purge shadow page