linux-kernel - [PATCH 51/52] KVM: MMU: Introduce gfn_to

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Date:	Sun, 30 Dec 2007 09:10:37 +0200
From:	Avi Kivity <avi@...ranet.com>
To:	linux-kernel@...r.kernel.org, kvm-devel@...ts.sourceforge.net
Subject: [PATCH 51/52] KVM: MMU: Introduce gfn_to_gpa()

Converting a frame number to an address is tricky since the data type changes
size.  Introduce a function to do it.  This fixes an actual bug when
accessing guest ptes.

Signed-off-by: Avi Kivity <avi@...ranet.com>
---
 drivers/kvm/kvm.h         |    4 ++++
 drivers/kvm/paging_tmpl.h |    4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index 048849d..eda82cd 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -499,6 +499,10 @@ static inline int memslot_id(struct kvm *kvm, struct kvm_memory_slot *slot)
 	return slot - kvm->memslots;
 }
 
+static inline gpa_t gfn_to_gpa(gfn_t gfn)
+{
+	return (gpa_t)gfn << PAGE_SHIFT;
+}
 
 enum kvm_stat_kind {
 	KVM_STAT_VM,
diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
index a3da98b..b24bc7c 100644
--- a/drivers/kvm/paging_tmpl.h
+++ b/drivers/kvm/paging_tmpl.h
@@ -110,7 +110,7 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
 		index = PT_INDEX(addr, walker->level);
 
 		table_gfn = gpte_to_gfn(pte);
-		pte_gpa = table_gfn << PAGE_SHIFT;
+		pte_gpa = gfn_to_gpa(table_gfn);
 		pte_gpa += index * sizeof(pt_element_t);
 		walker->table_gfn[walker->level - 1] = table_gfn;
 		pgprintk("%s: table_gfn[%d] %lx\n", __FUNCTION__,
@@ -442,7 +442,7 @@ static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr)
 	r = FNAME(walk_addr)(&walker, vcpu, vaddr, 0, 0, 0);
 
 	if (r) {
-		gpa = (gpa_t)walker.gfn << PAGE_SHIFT;
+		gpa = gfn_to_gpa(walker.gfn);
 		gpa |= vaddr & ~PAGE_MASK;
 	}
 
-- 
1.5.3.7

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