KVM: x86: extend usage of RET_MMIO_PF_* constants

The x86 MMU if full of code that returns 0 and 1 for retry/emulate.  Use
the existing RET_MMIO_PF_RETRY/RET_MMIO_PF_EMULATE enum, renaming it to
drop the MMIO part.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

CVE-2018-12207

(backported from commit 9b8ebbdb)
[tyhicks: Backport to 4.4
 - Some conditionals that checked for tracked pages did not exist due to
   the lack of commit 3d0c27ad ("KVM: MMU: let page fault handler be
   aware tracked page")
 - lower_32_bits(error_code) is not used in kvm_mmu_page_fault() due to
   the lack of commit 14727754 ("kvm: svm: Add support for
   additional SVM NPF error codes")]
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

arch/x86/kvm/mmu.c

@@ -140,6 +140,20 @@ module_param(dbg, bool, 0644);
 /* make pte_list_desc fit well in cache line */
 #define PTE_LIST_EXT 3
 
+/*
+ * Return values of handle_mmio_page_fault and mmu.page_fault:
+ * RET_PF_RETRY: let CPU fault again on the address.
+ * RET_PF_EMULATE: mmio page fault, emulate the instruction directly.
+ *
+ * For handle_mmio_page_fault only:
+ * RET_PF_INVALID: the spte is invalid, let the real page fault path update it.
+ */
+enum {
+	RET_PF_RETRY = 0,
+	RET_PF_EMULATE = 1,
+	RET_PF_INVALID = 2,
+};
+
 struct pte_list_desc {
 	u64 *sptes[PTE_LIST_EXT];
 	struct pte_list_desc *more;
@@ -2571,13 +2585,13 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 	return ret;
 }
 
-static bool mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned pte_access,
+static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned pte_access,
 			int write_fault, int level, gfn_t gfn, pfn_t pfn,
 			bool speculative, bool host_writable)
 {
 	int was_rmapped = 0;
 	int rmap_count;
-	bool emulate = false;
+	int ret = RET_PF_RETRY;
 
 	pgprintk("%s: spte %llx write_fault %d gfn %llx\n", __func__,
 		 *sptep, write_fault, gfn);
@@ -2607,12 +2621,12 @@ static bool mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned pte_access,
 	if (set_spte(vcpu, sptep, pte_access, level, gfn, pfn, speculative,
 	      true, host_writable)) {
 		if (write_fault)
-			emulate = true;
+			ret = RET_PF_EMULATE;
 		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
 	}
 
 	if (unlikely(is_mmio_spte(*sptep)))
-		emulate = true;
+		ret = RET_PF_EMULATE;
 
 	pgprintk("%s: setting spte %llx\n", __func__, *sptep);
 	pgprintk("instantiating %s PTE (%s) at %llx (%llx) addr %p\n",
@@ -2632,7 +2646,7 @@ static bool mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned pte_access,
 
 	kvm_release_pfn_clean(pfn);
 
-	return emulate;
+	return ret;
 }
 
 static pfn_t pte_prefetch_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn,
@@ -2772,14 +2786,13 @@ static int kvm_handle_bad_page(struct kvm_vcpu *vcpu, gfn_t gfn, pfn_t pfn)
 	 * Do not cache the mmio info caused by writing the readonly gfn
 	 * into the spte otherwise read access on readonly gfn also can
 	 * caused mmio page fault and treat it as mmio access.
-	 * Return 1 to tell kvm to emulate it.
 	 */
 	if (pfn == KVM_PFN_ERR_RO_FAULT)
-		return 1;
+		return RET_PF_EMULATE;
 
 	if (pfn == KVM_PFN_ERR_HWPOISON) {
 		kvm_send_hwpoison_signal(kvm_vcpu_gfn_to_hva(vcpu, gfn), current);
-		return 0;
+		return RET_PF_RETRY;
 	}
 
 	return -EFAULT;
@@ -3008,13 +3021,13 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, u32 error_code,
 	}
 
 	if (fast_page_fault(vcpu, v, level, error_code))
-		return 0;
+		return RET_PF_RETRY;
 
 	mmu_seq = vcpu->kvm->mmu_notifier_seq;
 	smp_rmb();
 
 	if (try_async_pf(vcpu, prefault, gfn, v, &pfn, write, &map_writable))
-		return 0;
+		return RET_PF_RETRY;
 
 	if (handle_abnormal_pfn(vcpu, v, gfn, pfn, ACC_ALL, &r))
 		return r;
@@ -3035,7 +3048,7 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, u32 error_code,
 out_unlock:
 	spin_unlock(&vcpu->kvm->mmu_lock);
 	kvm_release_pfn_clean(pfn);
-	return 0;
+	return RET_PF_RETRY;
 }
 
 
@@ -3362,54 +3375,38 @@ walk_shadow_page_get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
 	return reserved;
 }
 
-/*
- * 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;
 
 	if (mmio_info_in_cache(vcpu, addr, direct))
-		return RET_MMIO_PF_EMULATE;
+		return RET_PF_EMULATE;
 
 	reserved = walk_shadow_page_get_mmio_spte(vcpu, addr, &spte);
 	if (WARN_ON(reserved))
-		return RET_MMIO_PF_BUG;
+		return -EINVAL;
 
 	if (is_mmio_spte(spte)) {
 		gfn_t gfn = get_mmio_spte_gfn(spte);
 		unsigned access = get_mmio_spte_access(spte);
 
 		if (!check_mmio_spte(vcpu, spte))
-			return RET_MMIO_PF_INVALID;
+			return RET_PF_INVALID;
 
 		if (direct)
 			addr = 0;
 
 		trace_handle_mmio_page_fault(addr, gfn, access);
 		vcpu_cache_mmio_info(vcpu, addr, gfn, access);
-		return RET_MMIO_PF_EMULATE;
+		return RET_PF_EMULATE;
 	}
 
 	/*
 	 * If the page table is zapped by other cpus, let CPU fault again on
 	 * the address.
 	 */
-	return RET_MMIO_PF_RETRY;
+	return RET_PF_RETRY;
 }
 EXPORT_SYMBOL_GPL(handle_mmio_page_fault);
 
@@ -3522,13 +3519,13 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
 	}
 
 	if (fast_page_fault(vcpu, gpa, level, error_code))
-		return 0;
+		return RET_PF_RETRY;
 
 	mmu_seq = vcpu->kvm->mmu_notifier_seq;
 	smp_rmb();
 
 	if (try_async_pf(vcpu, prefault, gfn, gpa, &pfn, write, &map_writable))
-		return 0;
+		return RET_PF_RETRY;
 
 	if (handle_abnormal_pfn(vcpu, 0, gfn, pfn, ACC_ALL, &r))
 		return r;
@@ -3548,7 +3545,7 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
 out_unlock:
 	spin_unlock(&vcpu->kvm->mmu_lock);
 	kvm_release_pfn_clean(pfn);
-	return 0;
+	return RET_PF_RETRY;
 }
 
 static void nonpaging_init_context(struct kvm_vcpu *vcpu,
@@ -4393,24 +4390,24 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code,
 	enum emulation_result er;
 	bool direct = vcpu->arch.mmu.direct_map || mmu_is_nested(vcpu);
 
+	r = RET_PF_INVALID;
 	if (unlikely(error_code & PFERR_RSVD_MASK)) {
 		r = handle_mmio_page_fault(vcpu, cr2, direct);
-		if (r == RET_MMIO_PF_EMULATE) {
+		if (r == RET_PF_EMULATE) {
 			emulation_type = 0;
 			goto emulate;
 		}
-		if (r == RET_MMIO_PF_RETRY)
-			return 1;
-		if (r < 0)
-			return r;
-		/* Must be RET_MMIO_PF_INVALID.  */
 	}
 
+	if (r == RET_PF_INVALID) {
 		r = vcpu->arch.mmu.page_fault(vcpu, cr2, error_code, false);
+		WARN_ON(r == RET_PF_INVALID);
+	}
+
+	if (r == RET_PF_RETRY)
+		return 1;
 	if (r < 0)
 		return r;
-	if (!r)
-		return 1;
 
 	if (mmio_info_in_cache(vcpu, cr2, direct))
 		emulation_type = 0;

arch/x86/kvm/paging_tmpl.h

@@ -556,7 +556,7 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 	struct kvm_mmu_page *sp = NULL;
 	struct kvm_shadow_walk_iterator it;
 	unsigned direct_access, access = gw->pt_access;
-	int top_level, emulate;
+	int top_level, ret;
 
 	direct_access = gw->pte_access;
 
@@ -622,15 +622,15 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 	}
 
 	clear_sp_write_flooding_count(it.sptep);
-	emulate = mmu_set_spte(vcpu, it.sptep, gw->pte_access, write_fault,
+	ret = mmu_set_spte(vcpu, it.sptep, gw->pte_access, write_fault,
 			   it.level, gw->gfn, pfn, prefault, map_writable);
 	FNAME(pte_prefetch)(vcpu, gw, it.sptep);
 
-	return emulate;
+	return ret;
 
 out_gpte_changed:
 	kvm_release_pfn_clean(pfn);
-	return 0;
+	return RET_PF_RETRY;
 }
 
  /*
@@ -725,7 +725,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
 		if (!prefault)
 			inject_page_fault(vcpu, &walker.fault);
 
-		return 0;
+		return RET_PF_RETRY;
 	}
 
 	vcpu->arch.write_fault_to_shadow_pgtable = false;
@@ -747,7 +747,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
 
 	if (try_async_pf(vcpu, prefault, walker.gfn, addr, &pfn, write_fault,
 			 &map_writable))
-		return 0;
+		return RET_PF_RETRY;
 
 	if (handle_abnormal_pfn(vcpu, mmu_is_nested(vcpu) ? 0 : addr,
 				walker.gfn, pfn, walker.pte_access, &r))
@@ -792,7 +792,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
 out_unlock:
 	spin_unlock(&vcpu->kvm->mmu_lock);
 	kvm_release_pfn_clean(pfn);
-	return 0;
+	return RET_PF_RETRY;
 }
 
 static gpa_t FNAME(get_level1_sp_gpa)(struct kvm_mmu_page *sp)