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/
Home Products Support Community News


[Xen-ia64-devel] Re: [Xen-devel] [PATCH][RFC] 3/3 Fix [ia64] PV driver d

To: Alex Williamson <alex.williamson@xxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: [Xen-ia64-devel] Re: [Xen-devel] [PATCH][RFC] 3/3 Fix [ia64] PV driver domains - ugly python hacks
From: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
Date: Fri, 8 Aug 2008 14:19:55 +0900
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, xen-ia64-devel <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Thu, 07 Aug 2008 22:19:59 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <1218140434.4867.62.camel@lappy>
List-help: <mailto:xen-ia64-devel-request@lists.xensource.com?subject=help>
List-id: Discussion of the ia64 port of Xen <xen-ia64-devel.lists.xensource.com>
List-post: <mailto:xen-ia64-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-ia64-devel>, <mailto:xen-ia64-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-ia64-devel>, <mailto:xen-ia64-devel-request@lists.xensource.com?subject=unsubscribe>
References: <1218140434.4867.62.camel@lappy>
Sender: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mutt/1.5.6i
On Thu, Aug 07, 2008 at 02:20:34PM -0600, Alex Williamson wrote:
> x86 IOMMU support added a lot of assumptions about what PCI buses look
> like and where to find bridge devices.  On ia64, we don't yet have
> virtualization friendly IOMMUs, so for the moment, we just want to keep
> "unsafe" PV PCI pass through working as well as it did in Xen 3.2.
> Looking at the code, it almost seems like x86 has thrown out support for
> the old style driver domain.  Things that don't necessarily work on
> every PCI compliant architecture:
>       * You can't assume that just because there's a device at 01:01.0
>         that there's also a bridge at 01:00.0 and blow-up when you don't
>         find it.???  On HP ia64 boxes, PCI root bridges are not
>         necessarily exposed as a PCI device.  This pretty much means we
>         can't call into any of the "FLR" code paths.
>       * BAR alignment: it's hard to have BAR alignment when your page
>         size is 16k.  This wasn't a requirement for previous PV driver
>         domains, so I assume it's only for IOMMU support.
> This is ugly, so I'm open to suggestions.  It seems that all of these
> architecture checks could be replaced by checking some "iommu_present"
> variable to test whether the extra requirements are necessary.
> Signed-off-by: Alex Williamson <alex.williamson@xxxxxx>

Given that iommu is disabled on x86 by default,
this functional regression is accidental, I guess.
I think a sort of this patch is necessary for the next release.
(at least for IA64)


Xen-ia64-devel mailing list

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