From cec4fd80dbfa887c186959e7b4825f3fbf33ee87 Mon Sep 17 00:00:00 2001
From: Joerg Roedel <joerg.roedel@amd.com>
Date: Wed, 18 Feb 2009 14:08:58 +0100
Subject: [PATCH 5/5] KVM: MMU: handle compound pages in kvm_is_mmio_pfn

The function kvm_is_mmio_pfn is called before put_page is called on a
page by KVM. This is a problem when when this function is called on some
struct page which is part of a compund page. It does not test the
reserved flag of the compound page but of the struct page within the
compount page. This is a problem when KVM works with hugepages allocated
at boot time. These pages have the reserved bit set in all tail pages.
Only the flag in the compount head is cleared. KVM would not put such a
page which results in a memory leak.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
RH-Upstream-status: applied(kvm/master)
Bugzilla: 488727
Acked-by: Eduardo Habkost <ehabkost@redhat.com>
Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Acked-by: Andrea Arcangeli <aarcange@redhat.com>
---
 virt/kvm/kvm_main.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6e3f13b..247b8f8 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -581,8 +581,10 @@ static inline int valid_vcpu(int n)
 
 inline int kvm_is_mmio_pfn(pfn_t pfn)
 {
-	if (pfn_valid(pfn))
-		return PageReserved(pfn_to_page(pfn));
+	if (pfn_valid(pfn)) {
+		struct page *page = compound_head(pfn_to_page(pfn));
+		return PageReserved(page);
+	}
 
 	return true;
 }
-- 
1.6.1