KVM: x86/mmu: Add helpers to do full reserved SPTE checks w/ generic MMU

Extract the reserved SPTE check and print helpers in get_mmio_spte() to
new helpers so that KVM can also WARN on reserved badness when making a
SPTE.

Tag the checking helper with __always_inline to improve the probability
of the compiler generating optimal code for the checking loop, e.g. gcc
appears to avoid using %rbp when the helper is tagged with a vanilla
"inline".

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622175739.3610207-48-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2 files changed, 34 insertions, 21 deletions

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4676d696b909..ad025059a041 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3594,19 +3594,6 @@ static gpa_t nonpaging_gva_to_gpa_nested(struct kvm_vcpu *vcpu, gpa_t vaddr,
 	return vcpu->arch.nested_mmu.translate_gpa(vcpu, vaddr, access, exception);
 }
 
-static bool
-__is_rsvd_bits_set(struct rsvd_bits_validate *rsvd_check, u64 pte, int level)
-{
-	int bit7 = (pte >> 7) & 1;
-
-	return pte & rsvd_check->rsvd_bits_mask[bit7][level-1];
-}
-
-static bool __is_bad_mt_xwr(struct rsvd_bits_validate *rsvd_check, u64 pte)
-{
-	return rsvd_check->bad_mt_xwr & BIT_ULL(pte & 0x3f);
-}
-
 static bool mmio_info_in_cache(struct kvm_vcpu *vcpu, u64 addr, bool direct)
 {
 	/*
@@ -3684,13 +3671,7 @@ static bool get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
 	rsvd_check = &vcpu->arch.mmu->shadow_zero_check;
 
 	for (level = root; level >= leaf; level--)
-		/*
-		 * Use a bitwise-OR instead of a logical-OR to aggregate the
-		 * reserved bit and EPT's invalid memtype/XWR checks to avoid
-		 * adding a Jcc in the loop.
-		 */
-		reserved |= __is_bad_mt_xwr(rsvd_check, sptes[level]) |
-			    __is_rsvd_bits_set(rsvd_check, sptes[level], level);
+		reserved |= is_rsvd_spte(rsvd_check, sptes[level], level);
 
 	if (reserved) {
 		pr_err("%s: reserved bits set on MMU-present spte, addr 0x%llx, hierarchy:\n",
@@ -3698,7 +3679,7 @@ static bool get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
 		for (level = root; level >= leaf; level--)
 			pr_err("------ spte = 0x%llx level = %d, rsvd bits = 0x%llx",
 			       sptes[level], level,
-			       rsvd_check->rsvd_bits_mask[(sptes[level] >> 7) & 1][level-1]);
+			       get_rsvd_bits(rsvd_check, sptes[level], level));
 	}
 
 	return reserved;
diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
index bca0ba11cccf..7a5ce9314107 100644
--- a/arch/x86/kvm/mmu/spte.h
+++ b/arch/x86/kvm/mmu/spte.h
@@ -293,6 +293,38 @@ static inline bool is_dirty_spte(u64 spte)
 	return dirty_mask ? spte & dirty_mask : spte & PT_WRITABLE_MASK;
 }
 
+static inline u64 get_rsvd_bits(struct rsvd_bits_validate *rsvd_check, u64 pte,
+				int level)
+{
+	int bit7 = (pte >> 7) & 1;
+
+	return rsvd_check->rsvd_bits_mask[bit7][level-1];
+}
+
+static inline bool __is_rsvd_bits_set(struct rsvd_bits_validate *rsvd_check,
+				      u64 pte, int level)
+{
+	return pte & get_rsvd_bits(rsvd_check, pte, level);
+}
+
+static inline bool __is_bad_mt_xwr(struct rsvd_bits_validate *rsvd_check,
+				   u64 pte)
+{
+	return rsvd_check->bad_mt_xwr & BIT_ULL(pte & 0x3f);
+}
+
+static __always_inline bool is_rsvd_spte(struct rsvd_bits_validate *rsvd_check,
+					 u64 spte, int level)
+{
+	/*
+	 * Use a bitwise-OR instead of a logical-OR to aggregate the reserved
+	 * bits and EPT's invalid memtype/XWR checks to avoid an extra Jcc
+	 * (this is extremely unlikely to be short-circuited as true).
+	 */
+	return __is_bad_mt_xwr(rsvd_check, spte) |
+	       __is_rsvd_bits_set(rsvd_check, spte, level);
+}
+
 static inline bool spte_can_locklessly_be_made_writable(u64 spte)
 {
 	return (spte & shadow_host_writable_mask) &&