Re: [BUG] VFIO on POWER9 / QEMU fails to allocate 32-bit DMA

----- Original Message -----

From: "Ritesh Harjani" <ritesh.list@gmail.com>
To: "Timothy Pearson" <tpearson@raptorengineering.com>
Cc: "linuxppc-dev" <redacted>, "Shivaprasad G Bhat" <redacted>, "Gaurav Batra"
[off-list ref], "Madhavan Srinivasan" [off-list ref], "Venkat Rao Bagalkote" [off-list ref]
Sent: Sunday, August 16, 2026 7:22:18 PM
Subject: Re: [BUG] VFIO on POWER9 / QEMU fails to allocate 32-bit DMA

Hi Timothy

Timothy Pearson [off-list ref] writes:

quoted

----- Original Message -----

quoted

From: "Ritesh Harjani" <ritesh.list@gmail.com>
To: "Timothy Pearson" <tpearson@raptorengineering.com>
Cc: "linuxppc-dev" <redacted>, "Shivaprasad G Bhat"
[off-list ref], "Gaurav Batra"
[off-list ref], "Madhavan Srinivasan" [off-list ref], "Venkat Rao
Bagalkote" [off-list ref]
Sent: Saturday, August 8, 2026 9:13:09 AM
Subject: Re: [BUG] VFIO on POWER9 / QEMU fails to allocate 32-bit DMA

quoted

Timothy Pearson [off-list ref] writes:

quoted

----- Original Message -----
No worries, appreciated.  This is only one of several major problems with Linux
on PowerNV that we have run into after recent upgrades, and the primary focus
at the moment is on restoring broken functionality.  In many cases, that means
moving to different hardware, so gathering logs afterward can be difficult /
impossible.

Sorry to hear that you have been facing such issues recently. I will
bring this up internally. We will try to add more test matrix for
upstream PowerNV (note that we already have PowerNV tested regularly as
part of our upstream CI, but I suppose we could extend more KVM guest
testing there), so that we can reduce down on such reports.

That would be very helpful.  I have a number of other internal reports (and some
external customer reports) that I will try to get together for submission here.
Given the testing on PowerNV seems quite sparse at the moment, if you do need
additional PowerNV machines for testing we have bare metal cloud leases
available.

Thanks for bringing up your concern. Based on your feedback, we brought
up this topic internally. So currently w.r.t upstream maintainance work,
we have build, boot, selftests and few other test runs, on our PowerNV
systems, but I agree our other major testing was happening on Pseries
platform. So, we decided to add more PowerNV machines to our internal CI
and expand / increase our upstream CI tests and runs on these baremetal
machines too. This is going to happen very soon, so hopefully, this
should reduce such reports in the future.

I'm happy to hear this.  Would it be possible for you to share your intended hardware test matrix for PowerNV so that we can highlight any known gaps?  For example, AMD GPUs are very widely used on PowerNV platforms, but IBM doesn't test this combination to the best of my knowledge.

quoted

That sounds great, thanks.  Does IBM have any plans to support Debian LTS
(Freexian) so these patches can flow into the broken distribution kernels?

yes, we do support that. Once the patch is merged and available in
stable kernels, we will ensure this is backported to this distribution
as well.

That's great to hear!  Who should I use as a contact at IBM to put the Freexian team in contact with regarding the LTS support contract?

Thanks again!