[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH] spapr/pci: populate PCI DT in reverse order

From: Thomas Huth
Subject: Re: [Qemu-devel] [PATCH] spapr/pci: populate PCI DT in reverse order
Date: Fri, 24 Feb 2017 11:51:33 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0

On 22.02.2017 11:56, Greg Kurz wrote:
> From: Greg Kurz <address@hidden>
> This patch reverts to the historical SLOF ordering by walking PCI devices
> in reverse order. This reconciles pseries with x86 machine types behavior.
> It is expected to make things easier when porting existing applications to
> power.
> This patch was posted and already discussed during 2.5 development:
> http://patchwork.ozlabs.org/patch/549925/
> The "consensus" at the time was that guests should not rely on device
> ordering (i.e. use persistent naming instead).
> I got recently contacted by OpenStack people who had several complaints
> about the reverse ordering of PCI devices in pseries: different behavior
> between ppc64 and x86, lots of time spent in debugging when porting
> applications from x86 to ppc64 before realizing that it is caused by the
> reverse ordering, necessity to carry hacky workarounds...
> One strong argument against handling this properly with persistent naming
> is that it requires systemd/udev. This option is considered as painful
> with CirrOS, which aims at remaining as minimal as possible and is widely
> used in the OpenStack ecosystem.
> Would you re-consider your position and apply this patch ?

+1 for applying the patch.

During the past months, I've also run one or two times into issues with
the reversed ordering... fortunately, I was able to work around them (or
fix other bugs triggered by this), but I think it would be better to
return the the ascending order again to avoid further future problems.


reply via email to

[Prev in Thread] Current Thread [Next in Thread]