KVM: MMU: Make gfn_to_page() always safe

In case the page is not present in the guest memory map, return a dummy
page the guest can scribble on.

This simplifies error checking in its users.

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 5 insertions, 11 deletions

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index bbf5eb427dc6..2ad14fbdcfa0 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -850,23 +850,17 @@ static void page_header_update_slot(struct kvm *kvm, void *pte, gpa_t gpa)
         __set_bit(slot, &page_head->slot_bitmap);
 }
 
-hpa_t safe_gpa_to_hpa(struct kvm *kvm, gpa_t gpa)
-{
-        hpa_t hpa = gpa_to_hpa(kvm, gpa);
-
-        return is_error_hpa(hpa) ? bad_page_address | (gpa & ~PAGE_MASK): hpa;
-}
-
 hpa_t gpa_to_hpa(struct kvm *kvm, gpa_t gpa)
 {
         struct page *page;
+        hpa_t hpa;
 
         ASSERT((gpa & HPA_ERR_MASK) == 0);
         page = gfn_to_page(kvm, gpa >> PAGE_SHIFT);
-        if (!page)
-                return gpa | HPA_ERR_MASK;
-        return ((hpa_t)page_to_pfn(page) << PAGE_SHIFT)
-                | (gpa & (PAGE_SIZE-1));
+        hpa = ((hpa_t)page_to_pfn(page) << PAGE_SHIFT) | (gpa & (PAGE_SIZE-1));
+        if (is_error_page(page))
+                return hpa | HPA_ERR_MASK;
+        return hpa;
 }
 
 hpa_t gva_to_hpa(struct kvm_vcpu *vcpu, gva_t gva)