Re: [PATCH] kvm mmu: optimizations when tdp is in use

[Marcelo Tosatti <mtosatti@redhat.com>]

On Thu, May 27, 2010 at 04:06:34PM +0800, Gui Jianfeng wrote:
> In case of using tdp, checking write protected page isn't needed and
> quadrant also no need to be calculated.
> 
> Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
> ---
>  arch/x86/kvm/mmu.c |    7 +++++--
>  1 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 0bb9f17..ce4bbd3 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -495,10 +495,13 @@ static int mapping_level(struct kvm_vcpu *vcpu, gfn_t large_gfn)
>  	max_level = kvm_x86_ops->get_lpage_level() < host_level ?
>  		kvm_x86_ops->get_lpage_level() : host_level;
>  
> +	if (tdp_enabled)
> +		goto done;
> +

This is wrong. write_count is initialized for alignment purposes, not 
only write protected pages. See __kvm_set_memory_region in
virt/kvm/kvm_main.c.

>  	for (level = PT_DIRECTORY_LEVEL; level <= max_level; ++level)
>  		if (has_wrprotected_page(vcpu->kvm, large_gfn, level))
>  			break;
> -
> +done:
>  	return level - 1;
>  }
>  
> @@ -1346,7 +1349,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
>  	if (role.direct)
>  		role.cr4_pae = 0;
>  	role.access = access;
> -	if (vcpu->arch.mmu.root_level <= PT32_ROOT_LEVEL) {
> +	if (!tdp_enabled && vcpu->arch.mmu.root_level <= PT32_ROOT_LEVEL) {
>  		quadrant = gaddr >> (PAGE_SHIFT + (PT64_PT_BITS * level));
>  		quadrant &= (1 << ((PT32_PT_BITS - PT64_PT_BITS) * level)) - 1;
>  		role.quadrant = quadrant;
> -- 
> 1.6.5.2
> --
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