[PATCH 4.19 152/190] KVM: x86: optimize check for valid PAT value

Greg Kroah-Hartman
2019-09-13T13:18:33Z

[ Upstream commit 674ea351cdeb01d2740edce31db7f2d79ce6095d ]

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

Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kvm/mtrr.c | 10 +---------
arch/x86/kvm/vmx.c | 2 +-
arch/x86/kvm/x86.h | 10 ++++++++++
3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
index e9ea2d45ae66b..9f72cc427158e 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.c b/arch/x86/kvm/vmx.c
index ee9ff20da3902..feff7ed44a2bb 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4266,7 +4266,7 @@ 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 8889e0c029a70..3a91ea760f073 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -345,6 +345,16 @@ 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 & 0xF8F8F8F8F8F8F8F8ull)
+ return false;
+ /* 0, 1, 4, 5, 6, 7 are valid values. */
+ return (data | ((data & 0x0202020202020202ull) << 1)) == data;
+}
+
void kvm_load_guest_xcr0(struct kvm_vcpu *vcpu);
void kvm_put_guest_xcr0(struct kvm_vcpu *vcpu);
+
#endif
--
2.20.1