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RE: [Xen-devel] [bug] 'VT-d 1G super page' feature is blocked

  • To: Tim Deegan <tim@xxxxxxx>, "Ren, Yongjie" <yongjie.ren@xxxxxxxxx>
  • From: "Kay, Allen M" <allen.m.kay@xxxxxxxxx>
  • Date: Wed, 3 Aug 2011 10:58:15 -0700
  • Accept-language: en-US
  • Acceptlanguage: en-US
  • Cc: Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Li, Xin" <xin.li@xxxxxxxxx>
  • Delivery-date: Wed, 03 Aug 2011 11:02:30 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcxSAI6RSMtvx5MtS+eBGry1XIzq1AAA1VKA
  • Thread-topic: [Xen-devel] [bug] 'VT-d 1G super page' feature is blocked

Off hand, I don't see any reason iommu_setup() cannot be moved after 
do_presmp_initcalls() in __start_xen().

Theoretically, iommu_setup() just needs to be called before any device 
operation.  We should give it a try.


-----Original Message-----
From: Tim Deegan [mailto:tim@xxxxxxx] 
Sent: Wednesday, August 03, 2011 10:13 AM
To: Ren, Yongjie
Cc: Xen Devel; Kay, Allen M; Li, Xin
Subject: Re: [Xen-devel] [bug] 'VT-d 1G super page' feature is blocked

At 10:08 +0800 on 03 Aug (1312366080), Ren, Yongjie wrote:
> Hi Tim,
> Any comment on this issue ?
> It seems that cs# 23247 introduced this issue.


Allen points out that the EPT capability variable that is checked
doesn't get initialized until VMX is set up, which right now happens
_after_ the IOMMU is configured.

Allen, is there any reason that the call to iommu_enable() shouldn't be
moved to after do_presmp_initcalls()?  If so, then I guess we should
open-code the hardware capability check in the vtD init code. 


Tim Deegan <tim@xxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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