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>

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4676d69..ad02505 100644 (file)
--- 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 bca0ba1..7a5ce93 100644 (file)
--- 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) &&