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[Xen-devel] Re: [Question] Do we need to support devices that do not str

To: "Shan, Haitao" <haitao.shan@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [Question] Do we need to support devices that do not strictly follow the PCI-e specification?
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Thu, 09 Oct 2008 10:02:45 +0100
Cc: "Huang, Zhiteng" <zhiteng.huang@xxxxxxxxx>, "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>, "Li, Xin B" <xin.b.li@xxxxxxxxx>
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On 9/10/08 09:28, "Shan, Haitao" <haitao.shan@xxxxxxxxx> wrote:

Hi, Keir,
 
When debugging recently, I found some devices that did not follow the PCI-e specification strictly. Below is an example.

From PCI-e spec, PCI-e capability occupies 0x3c bytes of configuration space. Unimplemented registers are reserved and hardwired to zero. But for device listed below, PCI-e capability should begin at 0x4C and end at 0x88. But this device implements MSI, VPD, MSI-X capabilities in the reserved spaces. Current code can not handle this.

My question is do we need to add hacks to handle such kinds of devices?

I thought PCI capability offsets could be dynamically determined? If so, or there are other means to easily determine actual capability offsets without requiring explicit device-quirk lists, we should employ those means.

 -- Keir
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