From 681f8a610c1390c238f0bead17c974958833f830 Mon Sep 17 00:00:00 2001
From: Andrea Arcangeli <aarcange@redhat.com>
Date: Tue, 9 Mar 2010 14:20:09 -0300
Subject: [PATCH] avoid collision between out of sync ksm and pci passthrough

RH-Author: Andrea Arcangeli <aarcange@redhat.com>
Message-id: <20100309142009.GA28578@random.random>
Patchwork-id: 7612
O-Subject: avoid collision between out of sync ksm and pci passthrough
Bugzilla: 566385
RH-Acked-by: Izik Eidus <ieidus@redhat.com>
RH-Acked-by: Don Dutile <ddutile@redhat.com>
RH-Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
RH-Acked-by: Chris Wright <chrisw@redhat.com>

From: Andrea Arcangeli <aarcange@redhat.com>

This fixes a collision between the patch to allow out of sync on ksm pages
(that shall never become writable) and pci passthrough that maps invalid pfn in
the sptes. Patch is a noop for everything except pci passthrough.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
---

Please ACK, this is for 5.5 (hopefully) or 5.6.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
 arch/x86/kvm/paging_tmpl.h |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index e7226ba..c1f05c2 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -573,6 +573,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
 		offset = sp->role.quadrant << PT64_LEVEL_BITS;
 
 	for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
+		unsigned long pfn;
 		unsigned pte_access;
 		pt_element_t gpte;
 		gpa_t pte_gpa;
@@ -603,7 +604,8 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
 
 		nr_present++;
 		pte_access = sp->role.access & FNAME(gpte_access)(vcpu, gpte);
-		if (!PageAnon(pfn_to_page(spte_to_pfn(sp->spt[i]))))
+		pfn = spte_to_pfn(sp->spt[i]);
+		if (pfn_valid(pfn) && !PageAnon(pfn_to_page(pfn)))
 			pte_access &= ~PT_WRITABLE_MASK;
 		set_spte(vcpu, &sp->spt[i], pte_access, 0, 0,
 			 is_dirty_pte(gpte), 0, gpte & PT_GLOBAL_MASK, gfn,
-- 
1.6.3.rc4.29.g8146