Re: Radeon with 64k page size (ppc64 and others)

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> > On Wed, Jan 6, 2021 at 9:53 pm, Peter Robinson <pbrobinson@xxxxxxxxx>
> > wrote:
> >> Ultimately it's software bugs and if the software is open it's a
> >> fixable problem. Are there bugs filed? Because I've always found the
> >> IBM team that are involved in Fedora are pretty active on addressing
> >> those sorts of problems.
> >
> > Where do you want architecture-specific bugs to be filed? Is there some
> > component in Bugzilla for ppc64le issues?
> >
> > WebKit disables its heap security features ppc64le due to the 64 KB page
> > size. But reporting the bug to upstream would be pointless, because
> > upstream does not care about ppc64le. Reporting the bug against
> > webkit2gtk3 on Red Hat Bugzilla would mean reporting to myself, also not
> > very useful.
>
> GPUs also require firmware blobs, we can not really see inside them.  If
> there is something in the blob that only works on 4k then we have trouble.

Yes, I'm well aware, I've dealt with the difference between Fedora on
4K and RHEL/CentOS on 64K, I've engaged with vendors and they've
generally been receptive with bug reports even if they do sometimes
take a little while to fix them. There's some pretty big ppc64le
supercomputers running with GPUs with 64k page sizes for a number of
years:
https://www.olcf.ornl.gov/olcf-resources/compute-systems/summit/
https://computing.llnl.gov/computers/sierra

> These issues tend to crop up from time to time in different places, not
> just the kernel.  I started a thread[1] here with some of them.  For
> example, Firefox WebRTC with my Elgato Camlink was not working on 64k
> but it is fine on 4k.

Having done 4 architecture boot straps on Fedora, including the
ppc64le one, as well as being the non x85 release engineer for a
number of years I'm well aware of the problems involved, I've fixed
100s of bugs on ppc64le, armv7hl, aarch64, risc-v and s390x.

> Is there any way to report on how many packages call getconf PAGESIZE or
> getconf PAGE_SIZE during the build?  There are not many of these but
> they have different risks if people are swapping between 4k and 64k kernels.

The way I dealt with it on aarch64 was to check out all the packages
and sources, we've dealt with a lot of the key ones there on aarch64
because of the difference between Fedora on 4K and RHEL/CentOS on 64K.

> Most packages compiled on one type of kernel will run on the other type
> but there could be a very small number that have to be recompiled if the
> Fedora kernel changes down to 4k.

Yes, and the small number of packages would be bugs, just like bugs
between different architectures even if they're compiled with exactly
the same version of the toolchain and libraries. Welcome to non x86
architectures, I've been involved in !x86 for 11 years in a few weeks,
it's still a fun ride.

> Regardless of the packages above, I still think the Btrfs issue is the
> biggest surprise for people and it is worse because it is the default
> filesystem now.  People can reboot into a new kernel but they may not be
> able to easily reformat their disks after mkfs at 64k.

What's the situation on filesystems like xfs or ext4?
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