KVM: MMU: make return value of mmio page fault handler more readable

Define some meaningful names instead of raw code

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

3 files changed, 21 insertions, 12 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 5d9a1fb108f5..476d155834b9 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3224,17 +3224,12 @@ static u64 walk_shadow_page_get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr)
         return spte;
 }
 
-/*
- * If it is a real mmio page fault, return 1 and emulat the instruction
- * directly, return 0 to let CPU fault again on the address, -1 is
- * returned if bug is detected.
- */
 int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct)
 {
         u64 spte;
 
         if (quickly_check_mmio_pf(vcpu, addr, direct))
-                return 1;
+                return RET_MMIO_PF_EMULATE;
 
         spte = walk_shadow_page_get_mmio_spte(vcpu, addr);
 
@@ -3247,7 +3242,7 @@ int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct)
 
                 trace_handle_mmio_page_fault(addr, gfn, access);
                 vcpu_cache_mmio_info(vcpu, addr, gfn, access);
-                return 1;
+                return RET_MMIO_PF_EMULATE;
         }
 
         /*
@@ -3255,13 +3250,13 @@ int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct)
          * it's a BUG if the gfn is not a mmio page.
          */
         if (direct && !check_direct_spte_mmio_pf(spte))
-                return -1;
+                return RET_MMIO_PF_BUG;
 
         /*
          * If the page table is zapped by other cpus, let CPU fault again on
          * the address.
          */
-        return 0;
+        return RET_MMIO_PF_RETRY;
 }
 EXPORT_SYMBOL_GPL(handle_mmio_page_fault_common);
 
@@ -3271,7 +3266,7 @@ static int handle_mmio_page_fault(struct kvm_vcpu *vcpu, u64 addr,
         int ret;
 
         ret = handle_mmio_page_fault_common(vcpu, addr, direct);
-        WARN_ON(ret < 0);
+        WARN_ON(ret == RET_MMIO_PF_BUG);
         return ret;
 }
 
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 922bfae77c58..ba6a19c50f27 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -52,6 +52,20 @@
 
 int kvm_mmu_get_spte_hierarchy(struct kvm_vcpu *vcpu, u64 addr, u64 sptes[4]);
 void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask);
+
+/*
+ * Return values of handle_mmio_page_fault_common:
+ * RET_MMIO_PF_EMULATE: it is a real mmio page fault, emulate the instruction
+ *                       directly.
+ * RET_MMIO_PF_RETRY: let CPU fault again on the address.
+ * RET_MMIO_PF_BUG: bug is detected.
+ */
+enum {
+        RET_MMIO_PF_EMULATE = 1,
+        RET_MMIO_PF_RETRY = 0,
+        RET_MMIO_PF_BUG = -1
+};
+
 int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct);
 int kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *context);
 
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 78ee123de7a3..85c8d51dcbe7 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5366,10 +5366,10 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu)
         gpa = vmcs_read64(GUEST_PHYSICAL_ADDRESS);
 
         ret = handle_mmio_page_fault_common(vcpu, gpa, true);
-        if (likely(ret == 1))
+        if (likely(ret == RET_MMIO_PF_EMULATE))
                 return x86_emulate_instruction(vcpu, gpa, 0, NULL, 0) ==
                                               EMULATE_DONE;
-        if (unlikely(!ret))
+        if (unlikely(ret == RET_MMIO_PF_RETRY))
                 return 1;
 
         /* It is the real ept misconfig */