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Re: [Xen-devel] [PATCH] rombios: correct $PIR table router device ID

To: Ian Campbell <ian.campbell@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] rombios: correct $PIR table router device ID
From: Keir Fraser <keir.xen@xxxxxxxxx>
Date: Tue, 31 May 2011 15:59:57 +0100
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Thread-topic: [Xen-devel] [PATCH] rombios: correct $PIR table router device ID
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On 31/05/2011 14:55, "Ian Campbell" <ian.campbell@xxxxxxxxxx> wrote:

> Currently the $PIR table embedded in ROMBIOS refers to a "compatible PCI
> Interrupt Router" with Vendor/Device ID 8086:122e (Intel 82371FB, Original
> PIIX, I think), despite the fact that the Xen ioemu appears AFAICT to have
> never provided this particular device.
> Both the current qemu-xen and upstream qemu trees provide a device with ID
> 8086:1237 (Intel 82441, i440FX chipset) so switch to using this.
> Prior to 18931:0a393ba0ec0a the $PIR refered to an 8086:7000 (Intel 82371SB,
> PIIX3), which again AFAICT nothing ever provided...
> I've no idea which OSes actually pay attention to $PIR (Windows 98 perhaps?)
> and I certainly don't know what behaviour either the old/wrong or the
> new/"correct" value for this field will provoke. There's a strong arugment to
> be made for leaving well enough alone...

It doesn't have to be the *correct* device-id, just one that supports the
same method for programming with PCI-ISA links. See

If we change this we risk referring to a too-modern chipset for which old
OSes cannot find a matching driver. I suspect even the change to this in c/s
18931 (from upstream rombios) wasn't a tremendous idea.

Bear this in mind for seabios too. ;-)

 -- Keir

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