KVM: x86: simplify ept_misconfig

Calling handle_mmio_page_fault() has been unnecessary since commit
e9ee956e ("KVM: x86: MMU: Move handle_mmio_page_fault() call to
kvm_mmu_page_fault()", 2016-02-22).

handle_mmio_page_fault() can now be made static.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

CVE-2018-12207

(backported from commit e08d26f0)
[tyhicks: Backport to 4.4
 - Minor context change in handle_ept_misconfig() due to missing commit
   db1c056c ("kvm: vmx: Use the hardware provided GPA instead of
   page walk")]
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

arch/x86/kvm/mmu.c

@@ -3362,7 +3362,23 @@ walk_shadow_page_get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
 	return reserved;
 }
 
-int handle_mmio_page_fault(struct kvm_vcpu *vcpu, u64 addr, bool direct)
+/*
+ * Return values of handle_mmio_page_fault:
+ * RET_MMIO_PF_EMULATE: it is a real mmio page fault, emulate the instruction
+ *			directly.
+ * RET_MMIO_PF_INVALID: invalid spte is detected then let the real page
+ *			fault path update the mmio spte.
+ * RET_MMIO_PF_RETRY: let CPU fault again on the address.
+ * RET_MMIO_PF_BUG: a bug was detected (and a WARN was printed).
+ */
+enum {
+	RET_MMIO_PF_EMULATE = 1,
+	RET_MMIO_PF_INVALID = 2,
+	RET_MMIO_PF_RETRY = 0,
+	RET_MMIO_PF_BUG = -1
+};
+
+static int handle_mmio_page_fault(struct kvm_vcpu *vcpu, u64 addr, bool direct)
 {
 	u64 spte;
 	bool reserved;
@@ -4387,6 +4403,7 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code,
 			return 1;
 		if (r < 0)
 			return r;
+		/* Must be RET_MMIO_PF_INVALID.  */
 	}
 
 	r = vcpu->arch.mmu.page_fault(vcpu, cr2, error_code, false);

arch/x86/kvm/mmu.h

@@ -55,23 +55,6 @@ void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask);
 void
 reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context);
 
-/*
- * Return values of handle_mmio_page_fault:
- * RET_MMIO_PF_EMULATE: it is a real mmio page fault, emulate the instruction
- *			directly.
- * RET_MMIO_PF_INVALID: invalid spte is detected then let the real page
- *			fault path update the mmio spte.
- * RET_MMIO_PF_RETRY: let CPU fault again on the address.
- * RET_MMIO_PF_BUG: a bug was detected (and a WARN was printed).
- */
-enum {
-	RET_MMIO_PF_EMULATE = 1,
-	RET_MMIO_PF_INVALID = 2,
-	RET_MMIO_PF_RETRY = 0,
-	RET_MMIO_PF_BUG = -1
-};
-
-int handle_mmio_page_fault(struct kvm_vcpu *vcpu, u64 addr, bool direct);
 void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu);
 void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly);
 bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu);

arch/x86/kvm/vmx.c

@@ -6372,16 +6372,9 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu)
 						       NULL, 0) == EMULATE_DONE;
 	}
 
-	ret = handle_mmio_page_fault(vcpu, gpa, true);
-	if (likely(ret == RET_MMIO_PF_EMULATE))
-		return x86_emulate_instruction(vcpu, gpa, 0, NULL, 0) ==
-					      EMULATE_DONE;
-
-	if (unlikely(ret == RET_MMIO_PF_INVALID))
-		return kvm_mmu_page_fault(vcpu, gpa, 0, NULL, 0);
-
-	if (unlikely(ret == RET_MMIO_PF_RETRY))
-		return 1;
+	ret = kvm_mmu_page_fault(vcpu, gpa, PFERR_RSVD_MASK, NULL, 0);
+	if (ret >= 0)
+		return ret;
 
 	/* It is the real ept misconfig */
 	WARN_ON(1);