[PATCH] KVM: x86: optimize check for valid PAT value

[Paolo Bonzini]

This check will soon be done on every nested vmentry and vmexit,
"parallelize" it using bitwise operations.

Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
 arch/x86/kvm/mtrr.c    | 10 +---------
 arch/x86/kvm/vmx/vmx.c |  2 +-
 arch/x86/kvm/x86.h     |  8 ++++++++
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
index e9ea2d45ae66..9f72cc427158 100644
--- a/arch/x86/kvm/mtrr.c
+++ b/arch/x86/kvm/mtrr.c
@@ -48,11 +48,6 @@ static bool msr_mtrr_valid(unsigned msr)
        return false;
 }
 
-static bool valid_pat_type(unsigned t)
-{
-       return t < 8 && (1 << t) & 0xf3; /* 0, 1, 4, 5, 6, 7 */
-}
-
 static bool valid_mtrr_type(unsigned t)
 {
        return t < 8 && (1 << t) & 0x73; /* 0, 1, 4, 5, 6 */
@@ -67,10 +62,7 @@ bool kvm_mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data)
                return false;
 
        if (msr == MSR_IA32_CR_PAT) {
-               for (i = 0; i < 8; i++)
-                       if (!valid_pat_type((data >> (i * 8)) & 0xff))
-                               return false;
-               return true;
+               return kvm_pat_valid(data);
        } else if (msr == MSR_MTRRdefType) {
                if (data & ~0xcff)
                        return false;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b6c533afbf27..b74679732cfc 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1891,7 +1891,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct 
msr_data *msr_info)
                break;
        case MSR_IA32_CR_PAT:
                if (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PAT) {
-                       if (!kvm_mtrr_valid(vcpu, MSR_IA32_CR_PAT, data))
+                       if (!kvm_pat_valid(data))
                                return 1;
                        vmcs_write64(GUEST_IA32_PAT, data);
                        vcpu->arch.pat = data;
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 28406aa1136d..7bc7ac9d2a44 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -347,4 +347,12 @@ static inline void kvm_after_interrupt(struct kvm_vcpu 
*vcpu)
        __this_cpu_write(current_vcpu, NULL);
 }
 
+static inline bool kvm_pat_valid(u64 data)
+{
+       if (data & 0xF8F8F8F8F8F8F8F8)
+               return false;
+       /* 0, 1, 4, 5, 6, 7 are valid values.  */
+       return (data | ((data & 0x0202020202020202) << 1)) == data;
+}
+
 #endif
-- 
1.8.3.1