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xen-devel
Re: [Xen-devel] [Patch] Add VMX memory-mapped Local APIC access optimiza
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To: |
"Cui, Dexuan" <dexuan.cui@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx> |
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Subject: |
Re: [Xen-devel] [Patch] Add VMX memory-mapped Local APIC access optimization |
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From: |
Keir Fraser <keir@xxxxxxxxxxxxx> |
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Date: |
Wed, 30 May 2007 17:32:09 +0100 |
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Cc: |
"Li, Xin B" <xin.b.li@xxxxxxxxx>, "Dong, Eddie" <eddie.dong@xxxxxxxxx>, "Nakajima, Jun" <jun.nakajima@xxxxxxxxx> |
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Wed, 30 May 2007 09:31:18 -0700 |
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[Xen-devel] [Patch] Add VMX memory-mapped Local APIC access optimization |
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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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