Re: [PATCH 6/5] KVM: MMU: Optimize is_last_gpte()

From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
To: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>, kvm@vger.kernel.org
Subject: Re: [PATCH 6/5] KVM: MMU: Optimize is_last_gpte()
Date: Thu, 13 Sep 2012 21:39:17 +0800	[thread overview]
Message-ID: <5051E205.5090400@linux.vnet.ibm.com> (raw)
In-Reply-To: <5051ABCA.8080300@redhat.com>

On 09/13/2012 05:47 PM, Avi Kivity wrote:
> On 09/12/2012 09:03 PM, Avi Kivity wrote:
>> On 09/12/2012 08:49 PM, Avi Kivity wrote:
>>> Instead of branchy code depending on level, gpte.ps, and mmu configuration,
>>> prepare everything in a bitmap during mode changes and look it up during
>>> runtime.
>>
>> 6/5 is buggy, sorry, will update it tomorrow.
>>
>>
> 
> --------8<----------8<--------------
> 
> From: Avi Kivity <avi@redhat.com>
> Date: Wed, 12 Sep 2012 20:46:56 +0300
> Subject: [PATCH v2 6/5] KVM: MMU: Optimize is_last_gpte()
> 
> Instead of branchy code depending on level, gpte.ps, and mmu configuration,
> prepare everything in a bitmap during mode changes and look it up during
> runtime.
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
> 
> v2: rearrange bitmap (one less shift)
>     avoid stomping on local variable
>     fix index calculation
>     move check back to a function
> 
>  arch/x86/include/asm/kvm_host.h |  7 +++++++
>  arch/x86/kvm/mmu.c              | 31 +++++++++++++++++++++++++++++++
>  arch/x86/kvm/mmu.h              |  3 ++-
>  arch/x86/kvm/paging_tmpl.h      | 22 +---------------------
>  4 files changed, 41 insertions(+), 22 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 3318bde..f9a48cf 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -298,6 +298,13 @@ struct kvm_mmu {
>  	u64 *lm_root;
>  	u64 rsvd_bits_mask[2][4];
> 
> +	/*
> +	 * Bitmap: bit set = last pte in walk
> +	 * index[0]: pte.ps
> +	 * index[1:2]: level
> +	 */

Opposite? index[2]: pte.pse?

Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>