KVM: MMU: Keep going on permission error

Real hardware disregards permission errors when computing page fault error
code bit 0 (page present).  Do the same.

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

1 files changed, 30 insertions, 22 deletions

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 3a3f6d784d79..1cea41cad069 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -119,21 +119,25 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
 {
         pt_element_t pte;
         gfn_t table_gfn;
-        unsigned index, pt_access, pte_access;
+        unsigned index, pt_access, uninitialized_var(pte_access);
         gpa_t pte_gpa;
-        int rsvd_fault = 0;
+        bool eperm, present, rsvd_fault;
 
         trace_kvm_mmu_pagetable_walk(addr, write_fault, user_fault,
                                      fetch_fault);
 walk:
+        present = true;
+        eperm = rsvd_fault = false;
         walker->level = vcpu->arch.mmu.root_level;
         pte = vcpu->arch.cr3;
 #if PTTYPE == 64
         if (!is_long_mode(vcpu)) {
                 pte = kvm_pdptr_read(vcpu, (addr >> 30) & 3);
                 trace_kvm_mmu_paging_element(pte, walker->level);
-                if (!is_present_gpte(pte))
-                        goto not_present;
+                if (!is_present_gpte(pte)) {
+                        present = false;
+                        goto error;
+                }
                 --walker->level;
         }
 #endif
@@ -151,31 +155,36 @@ walk:
                 walker->table_gfn[walker->level - 1] = table_gfn;
                 walker->pte_gpa[walker->level - 1] = pte_gpa;
 
-                if (kvm_read_guest(vcpu->kvm, pte_gpa, &pte, sizeof(pte)))
-                        goto not_present;
+                if (kvm_read_guest(vcpu->kvm, pte_gpa, &pte, sizeof(pte))) {
+                        present = false;
+                        break;
+                }
 
                 trace_kvm_mmu_paging_element(pte, walker->level);
 
-                if (!is_present_gpte(pte))
-                        goto not_present;
+                if (!is_present_gpte(pte)) {
+                        present = false;
+                        break;
+                }
 
-                rsvd_fault = is_rsvd_bits_set(vcpu, pte, walker->level);
-                if (rsvd_fault)
-                        goto access_error;
+                if (is_rsvd_bits_set(vcpu, pte, walker->level)) {
+                        rsvd_fault = true;
+                        break;
+                }
 
                 if (write_fault && !is_writable_pte(pte))
                         if (user_fault || is_write_protection(vcpu))
-                                goto access_error;
+                                eperm = true;
 
                 if (user_fault && !(pte & PT_USER_MASK))
-                        goto access_error;
+                        eperm = true;
 
 #if PTTYPE == 64
                 if (fetch_fault && (pte & PT64_NX_MASK))
-                        goto access_error;
+                        eperm = true;
 #endif
 
-                if (!(pte & PT_ACCESSED_MASK)) {
+                if (!eperm && !rsvd_fault && !(pte & PT_ACCESSED_MASK)) {
                         trace_kvm_mmu_set_accessed_bit(table_gfn, index,
                                                        sizeof(pte));
                         if (FNAME(cmpxchg_gpte)(vcpu->kvm, table_gfn,
@@ -214,6 +223,9 @@ walk:
                 --walker->level;
         }
 
+        if (!present || eperm || rsvd_fault)
+                goto error;
+
         if (write_fault && !is_dirty_gpte(pte)) {
                 bool ret;
 
@@ -233,14 +245,10 @@ walk:
                  __func__, (u64)pte, pte_access, pt_access);
         return 1;
 
-not_present:
+error:
         walker->error_code = 0;
-        goto err;
-
-access_error:
-        walker->error_code = PFERR_PRESENT_MASK;
-
-err:
+        if (present)
+                walker->error_code |= PFERR_PRESENT_MASK;
         if (write_fault)
                 walker->error_code |= PFERR_WRITE_MASK;
         if (user_fault)