[PATCH 7/8] KVM: Optimize kvm_read_cr[04]_bits()

Avi Kivity
2010-01-21T13:31:55Z

'mask' is always a constant, so we can check whether it includes a bit that
might be owned by the guest very cheaply, and avoid the decache call. Saves
a few hundred bytes of module text.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
arch/x86/kvm/kvm_cache_regs.h | 9 +++++++--
1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/kvm_cache_regs.h b/arch/x86/kvm/kvm_cache_regs.h
index 6b419a3..5a109c6 100644
--- a/arch/x86/kvm/kvm_cache_regs.h
+++ b/arch/x86/kvm/kvm_cache_regs.h
@@ -1,6 +1,9 @@
#ifndef ASM_KVM_CACHE_REGS_H
#define ASM_KVM_CACHE_REGS_H

+#define KVM_POSSIBLE_CR0_GUEST_BITS X86_CR0_TS
+#define KVM_POSSIBLE_CR4_GUEST_BITS X86_CR4_PGE
+
static inline unsigned long kvm_register_read(struct kvm_vcpu *vcpu,
enum kvm_reg reg)
{
@@ -40,7 +43,8 @@ static inline u64 kvm_pdptr_read(struct kvm_vcpu *vcpu, int index)

static inline ulong kvm_read_cr0_bits(struct kvm_vcpu *vcpu, ulong mask)
{
- if (mask & vcpu->arch.cr0_guest_owned_bits)
+ ulong tmask = mask & KVM_POSSIBLE_CR0_GUEST_BITS;
+ if (tmask & vcpu->arch.cr0_guest_owned_bits)
kvm_x86_ops->decache_cr0_guest_bits(vcpu);
return vcpu->arch.cr0 & mask;
}
@@ -52,7 +56,8 @@ static inline ulong kvm_read_cr0(struct kvm_vcpu *vcpu)

static inline ulong kvm_read_cr4_bits(struct kvm_vcpu *vcpu, ulong mask)
{
- if (mask & vcpu->arch.cr4_guest_owned_bits)
+ ulong tmask = mask & KVM_POSSIBLE_CR4_GUEST_BITS;
+ if (tmask & vcpu->arch.cr4_guest_owned_bits)
kvm_x86_ops->decache_cr4_guest_bits(vcpu);
return vcpu->arch.cr4 & mask;
}
--
1.6.5.3