Re: [Xen-devel] [BUG] After upgrade to Xen 4.12.0 iommu=no-igfx

[Roman Shaposhnik <roman@xxxxxxxxxx>]

On Thu, Aug 1, 2019 at 1:45 AM Roger Pau Monné <roger.pau@xxxxxxxxxx> wrote:
>
> On Wed, Jul 31, 2019 at 12:30:04PM -0700, Roman Shaposhnik wrote:
> > On Wed, Jul 31, 2019 at 1:36 AM Roger Pau Monné <roger.pau@xxxxxxxxxx> 
> > wrote:
> > >
> > > On Tue, Jul 30, 2019 at 10:55:24AM -0700, Roman Shaposhnik wrote:
> > > > Sorry -- got a bit distracted yesterday. Attached is the log with only
> > > > your latest patch attached. Interestingly enough the box booted fine
> > > > without screen artifacts. So I guess we're getting closer...
> > > >
> > > > Thanks for all the help!
> > >
> > > That's quite weird, there's no functional changes between the
> > > previous patches and this one, the only difference is that this patch
> > > has more verbose output.
> >
> > That's super weird indeed. I'm re-trying your very first patch right
> > now to see if it may be a pilot error on my part (hope not).
> >
> > > Are you sure you didn't have any local patches on top of Xen that
> > > could explain this difference in behaviour?
> >
> > Pretty sure -- but let me push my branch in EVE and show to you all
> > (you will need Docker installed to build Xen the way EVE does).
>
> I'm afraid it's quite hard for me to figure out whether you have any
> patches on top of Xen or not.

It is actually super simple. We use Docker containers as method for
guaranteeing that our build environment is always pristine and controlled.
Precisely to avoid this type of issues like random patches getting in, etc.

So... let me explain (not so much to convince you to use it, but rather
to have an extra pair of eye on an off chance that I actually missed
something):

All of our builds steps are captured in the following Dockerfile:
      https://github.com/rvs/eve/blob/xen-bug/pkg/xen/Dockerfile
it is based on Alpine Linux 3.7 and we only install the following
packages into a printing Alpine:
      https://github.com/rvs/eve/blob/xen-bug/pkg/xen/Dockerfile#L5
then we proceed with downloading Xen from a printing upsteram
tarball:
      https://github.com/rvs/eve/blob/xen-bug/pkg/xen/Dockerfile#L36
and only apply patches that sit next to the Dockerfile and have
patch file extension:
      https://github.com/rvs/eve/blob/xen-bug/pkg/xen/Dockerfile#L50

At this point this is a single patch:
      https://github.com/rvs/eve/blob/xen-bug/pkg/xen/01-iommu-mappings.patch
there's literally nothing else in that folder:
      https://github.com/rvs/eve/blob/xen-bug/pkg/xen

Then we proceed with building Xen in a very vanilla fashion:
      https://github.com/rvs/eve/blob/xen-bug/pkg/xen/Dockerfile#L64

That's it! That's literally all the build logic.

> For further testing can you make sure you don't have any custom
> patches on top of Xen (if you indeed had any in the previous
> attempts)?

I don't think there's any way for extra patches to sneak in, but please
see the above explanation.

Thanks,
Roman.

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