Messages in this thread | | | Date | Mon, 12 Apr 2010 11:34:47 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH 4/6] KVM MMU: optimize for writing cr4 |
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On 04/12/2010 11:03 AM, Xiao Guangrong wrote: > 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; >
Later we have:
> kvm_x86_ops->set_cr4(vcpu, cr4); > vcpu->arch.cr4 = cr4; > vcpu->arch.mmu.base_role.cr4_pge = (cr4 & X86_CR4_PGE) && > !tdp_enabled;
All of which depend on cr4.
-- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.
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