linux-kernel - [PATCH 27/33] KVM: MMU: Treat user-mode faults as a hint that a page is no longer a page table

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Date:	Thu, 04 Jan 2007 16:16:07 -0000
From:	Avi Kivity <avi@...ranet.com>
To:	kvm-devel@...ts.sourceforge.net
Cc:	linux-kernel@...r.kernel.org, akpm@...l.org, mingo@...e.hu
Subject: [PATCH 27/33] KVM: MMU: Treat user-mode faults as a hint that a page
	is no longer a page table

Signed-off-by: Avi Kivity <avi@...ranet.com>

Index: linux-2.6/drivers/kvm/paging_tmpl.h
===================================================================
--- linux-2.6.orig/drivers/kvm/paging_tmpl.h
+++ linux-2.6/drivers/kvm/paging_tmpl.h
@@ -271,6 +271,7 @@ static int FNAME(fix_write_pf)(struct kv
 	pt_element_t *guest_ent;
 	int writable_shadow;
 	gfn_t gfn;
+	struct kvm_mmu_page *page;
 
 	if (is_writeble_pte(*shadow_ent))
 		return 0;
@@ -303,7 +304,17 @@ static int FNAME(fix_write_pf)(struct kv
 	}
 
 	gfn = walker->gfn;
-	if (kvm_mmu_lookup_page(vcpu, gfn)) {
+
+	if (user) {
+		/*
+		 * Usermode page faults won't be for page table updates.
+		 */
+		while ((page = kvm_mmu_lookup_page(vcpu, gfn)) != NULL) {
+			pgprintk("%s: zap %lx %x\n",
+				 __FUNCTION__, gfn, page->role.word);
+			kvm_mmu_zap_page(vcpu, page);
+		}
+	} else if (kvm_mmu_lookup_page(vcpu, gfn)) {
 		pgprintk("%s: found shadow page for %lx, marking ro\n",
 			 __FUNCTION__, gfn);
 		*write_pt = 1;
-
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