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Subject[PATCH 19/38] KVM: Optimize kvm_read_cr[04]_bits()
Date
'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>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---
arch/x86/kvm/kvm_cache_regs.h | 11 +++++++++--
1 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/kvm_cache_regs.h b/arch/x86/kvm/kvm_cache_regs.h
index 6b419a3..cff851c 100644
--- a/arch/x86/kvm/kvm_cache_regs.h
+++ b/arch/x86/kvm/kvm_cache_regs.h
@@ -1,6 +1,11 @@
#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_PVI | X86_CR4_DE | X86_CR4_PCE | X86_CR4_OSFXSR \
+ | X86_CR4_OSXMMEXCPT | X86_CR4_PGE)
+
static inline unsigned long kvm_register_read(struct kvm_vcpu *vcpu,
enum kvm_reg reg)
{
@@ -40,7 +45,8 @@ 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 +58,8 @@ 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


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