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

[Timothy Pearson <tpearson@raptorengineering.com>]

----- Original Message -----
> From: "Ritesh Harjani" <ritesh.list@gmail.com>
> To: "Timothy Pearson" <tpearson@raptorengineering.com>
> Cc: "linuxppc-dev" <linuxppc-dev@lists.ozlabs.org>, "Shivaprasad G Bhat" <sbhat@linux.ibm.com>, "Gaurav Batra"
> <gbatra@linux.ibm.com>, "Madhavan Srinivasan" <maddy@linux.ibm.com>, "Venkat Rao Bagalkote" <venkat88@linux.ibm.com>
> 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 <tpearson@raptorengineering.com> writes:
> 
>> ----- Original Message -----
>>> From: "Ritesh Harjani" <ritesh.list@gmail.com>
>>> To: "Timothy Pearson" <tpearson@raptorengineering.com>
>>> Cc: "linuxppc-dev" <linuxppc-dev@lists.ozlabs.org>, "Shivaprasad G Bhat"
>>> <sbhat@linux.ibm.com>, "Gaurav Batra"
>>> <gbatra@linux.ibm.com>, "Madhavan Srinivasan" <maddy@linux.ibm.com>, "Venkat Rao
>>> Bagalkote" <venkat88@linux.ibm.com>
>>> Sent: Saturday, August 8, 2026 9:13:09 AM
>>> Subject: Re: [BUG] VFIO on POWER9 / QEMU fails to allocate 32-bit DMA
>>
>>> Timothy Pearson <tpearson@raptorengineering.com> writes:
>>> 
>>>> ----- 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.

>> 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!