RE: [Xen-devel] [Patch] Add VMX memory-mapped Local APIC access optimization

["Cui, Dexuan" <dexuan.cui@xxxxxxxxx>]

Keir,
Thanks a lot for the simplification!  :)
I made some simple tests, and verified at least on my host the vTPR feature 
really works and the performance of SMP Windows 2003 Guest behaves much better.

-- Dexuan

-----Original Message-----
From: Keir Fraser [mailto:keir@xxxxxxxxxxxxx] 
Sent: 2007年5月31日 0:32
To: Cui, Dexuan; xen-devel@xxxxxxxxxxxxxxxxxxx
Cc: Li, Xin B; Dong, Eddie; Nakajima, Jun
Subject: Re: [Xen-devel] [Patch] Add VMX memory-mapped Local APIC access 
optimization

Applied but I've subsequently 'simplified' it quite a bit. :-) You'll want
to pull it from the staging tree and make sure it actually still works.

 -- Keir

On 17/5/07 07:52, "Cui, Dexuan" <dexuan.cui@xxxxxxxxx> wrote:

> Some operating systems access the local APIC TPR very frequently, and we
> handle that using software-based local APIC virtualization in Xen today.
> Such virtualization incurs a number of VM exits from the memory-access
> instructions against the APIC page in the guest.
> 
> The attached patch enables the TPR shadow feature that provides APIC TPR
> virtualization in hardware. Our tests indicate it can significantly
> boost the performance of such guests including 32-bit Windows XP/2003.
> 
> Moreover, with the patch, local APIC accesses other than TPR in guests
> are intercepted directly as APIC_ACCESS VM exits rather than PAGE_FAULT
> VM exits; this can lower the emulation cost of such accesses.
> 
> Signed-off-by: Dexuan Cui <dexuan.cui@xxxxxxxxx>
> 
> PS, the related document is available in the latest Intel SDM 3B:
> http://www.intel.com/products/processor/manuals/index.htm
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel

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