KVM: MMU: filter out the mmio pfn from the fault pfn

If the page fault is caused by mmio, the gfn can not be found in memslots, and
'bad_pfn' is returned on gfn_to_hva path, so we can use 'bad_pfn' to identify
the mmio page fault.
And, to clarify the meaning of mmio pfn, we return fault page instead of bad
page when the gfn is not allowd to prefetch

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

3 files changed, 21 insertions, 4 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 5334b4e9ecc7..96a7ed4e6837 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2085,8 +2085,8 @@ static pfn_t pte_prefetch_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn,
 
         slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, no_dirty_log);
         if (!slot) {
-                get_page(bad_page);
-                return page_to_pfn(bad_page);
+                get_page(fault_page);
+                return page_to_pfn(fault_page);
         }
 
         hva = gfn_to_hva_memslot(slot, gfn);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index c8e023902f79..eabb21a30c34 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -327,12 +327,17 @@ static inline struct kvm_memslots *kvm_memslots(struct kvm *kvm)
 static inline int is_error_hpa(hpa_t hpa) { return hpa >> HPA_MSB; }
 
 extern struct page *bad_page;
+extern struct page *fault_page;
+
 extern pfn_t bad_pfn;
+extern pfn_t fault_pfn;
 
 int is_error_page(struct page *page);
 int is_error_pfn(pfn_t pfn);
 int is_hwpoison_pfn(pfn_t pfn);
 int is_fault_pfn(pfn_t pfn);
+int is_noslot_pfn(pfn_t pfn);
+int is_invalid_pfn(pfn_t pfn);
 int kvm_is_error_hva(unsigned long addr);
 int kvm_set_memory_region(struct kvm *kvm,
                           struct kvm_userspace_memory_region *mem,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d5ef9ebcaff7..56f3c704fd74 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -101,8 +101,8 @@ static bool largepages_enabled = true;
 static struct page *hwpoison_page;
 static pfn_t hwpoison_pfn;
 
-static struct page *fault_page;
-static pfn_t fault_pfn;
+struct page *fault_page;
+pfn_t fault_pfn;
 
 inline int kvm_is_mmio_pfn(pfn_t pfn)
 {
@@ -931,6 +931,18 @@ int is_fault_pfn(pfn_t pfn)
 }
 EXPORT_SYMBOL_GPL(is_fault_pfn);
 
+int is_noslot_pfn(pfn_t pfn)
+{
+        return pfn == bad_pfn;
+}
+EXPORT_SYMBOL_GPL(is_noslot_pfn);
+
+int is_invalid_pfn(pfn_t pfn)
+{
+        return pfn == hwpoison_pfn || pfn == fault_pfn;
+}
+EXPORT_SYMBOL_GPL(is_invalid_pfn);
+
 static inline unsigned long bad_hva(void)
 {
         return PAGE_OFFSET;