[PATCH 4/6] KVM MMU: optimize for writing cr4

Xiao Guangrong
2010-04-12T08:03:44Z

Usually, OS changes CR4.PGE bit to flush all global page, under this
case, no need reset mmu and just flush tlb

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
arch/x86/kvm/x86.c | 9 +++++++++
1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fd5c3d3..2aaa6fb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -463,6 +463,15 @@ void kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
unsigned long old_cr4 = kvm_read_cr4(vcpu);
unsigned long pdptr_bits = X86_CR4_PGE | X86_CR4_PSE | X86_CR4_PAE;

+ if (cr4 == old_cr4)
+ return;
+
+ if ((cr4 ^ old_cr4) == X86_CR4_PGE) {
+ kvm_mmu_sync_roots(vcpu);
+ kvm_mmu_flush_tlb(vcpu);
+ return;
+ }
+
if (cr4 & CR4_RESERVED_BITS) {
kvm_inject_gp(vcpu, 0);
return;
--
1.6.1.2