WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

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

To: Keir Fraser <keir.xen@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] rombios: correct $PIR table router device ID
From: Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>
Date: Tue, 31 May 2011 16:06:51 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Tue, 31 May 2011 08:11:53 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <CA0AC0FD.1B532%keir.xen@xxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Organization: Citrix Systems, Inc.
References: <CA0AC0FD.1B532%keir.xen@xxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
On Tue, 2011-05-31 at 15:59 +0100, Keir Fraser wrote:
> 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
> http://www.microsoft.com/taiwan/whdc/archive/pciirq.mspx.

Ah so an OSes won't (or isn't supposed to) go looking for an actual
device with that specific ID but rather uses it as a key into its table
of ways of dealing with PCI-ISA links to find an alternative driver. I
should have read the document closer (in fairness the reality of these
semantics seem pretty unimaginable!).

> 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. ;-)

That was really why I posted this patch ;-) I'll stick with the old ID
throughout.

Ian.



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

<Prev in Thread] Current Thread [Next in Thread>