Dave Airlie Linux Graphics blog

Software Engineering Radio is a podcast for people in IT/development with over 700 episodes across many topics over 20 years. They haven't touched on the Linux kernel much. I was invited on as part of my role at Red Hat as a Distinguished Engineer, but the podcast is really an insight into kernel maintenance, in graphics and beyond, touching on the scope and scale of the project. It was my first time to record something that wasn't just me talking at a conference/meetup, and it was all very professional, with sound checks and brainstorming before hand.  The content is at a pretty broad and introductory level. We talked about kernel development processes, maintenance processes, and we touch on rust in the kernel a bit. It's mostly about the sheer size and scale of the project and how Linus releases things, how trees get to Linus and how the GPU work is done.  Hopefully you enjoy listening to it! [1] https://se-radio.net/2026/06/se-radio-723-dave-airlie-on-linux-kernel-mainte...

I'm doing a podcast recording this week, so I wanted to run some numbers so I could have some facts rather than feels. It turns out my feels were off by a factor of 3 or so. If asked, I've always said the contributor count to the drm subsystem is probably in the 100 or so developers per release cycle. Did the simplest: git log --format='%aN' v6.14..v6.15 drivers/gpu/drm/ include/uapi/drm/ include/drm/ | sort -u | wc -l Iterated over a few kernel releases v6.15 326 v6.16 322 v6.17 300 v6.18 334 v6.19 332 v7.0-rc6 346  The number for the complete kernel in those scenarios are ~2000 usually, which means drm subsystem has around 15-16% of the kernel contributors. I'm a bit spun out, that's quite a lot of people. I think I'll blame Sima for it. This also explains why I'm a bit out of touch with the process problems other maintainers have, and when I say stuff like a lot of workflows don't scale, this is what I mean.    

This topic came up at kernel maintainers summit and some other groups have been playing around with it, particularly the BPF folks, and Chris Mason's work on kernel review prompts[1] for regressions. Red Hat have asked engineers to investigate some workflow enhancements with AI tooling, so I decided to let the vibecoding off the leash. My main goal: - Provide AI led patch review for drm patches - Don't pollute the mailing list with them at least initially. This led me to wanting to use lei/b4 tools, and public-inbox. If I could push the patches with message-ids and the review reply to a public-inbox I could just publish that and point people at it, and they could consume it using lei into their favorite mbox or browse it on the web. I got claude to run with this idea, and it produced a project [2] that I've been refining for a couple of days. I started with trying to use Chris' prompts, but screwed that up a bit due to sandboxing, but then I started iterating on using t...

Just to keep up some blogging content, I'll do where did I spend/waste time last couple of weeks. I was working on two nouveau kernel bugs in parallel (in between whatever else I was doing). Bug 1: Lyude, 2 or 3 weeks ago identified the RTX6000 Ada GPU wasn't resuming from suspend. I plugged in my one and indeed it wasn't. Turned out since we moved to 570 firmware, this has been broken. We started digging down various holes on what changed, sent NVIDIA debug traces to decode for us. NVIDIA identified that suspend was actually failing but the result wasn't getting propogated up. At least the opengpu driver was working properly. I started writing patches for all the various differences between nouveau and opengpu in terms of what we send to the firmware, but none of them were making a difference. I took a tangent, and decided to try and drop the latest 570.207 firmware into place instead of 570.144. NVIDIA have made attempts to keep the firmware in one stream more ABI sta...

F43 picked up the two patches I created to fix a bunch of deadlocks on laptops reported in my previous blog posting. Turns out Vulkan layers have a subtle thing I missed, and I removed a line from the device select layer that would only matter if you have another layer, which happens under steam. The fedora update process caught this, but it still got published which was a mistake, need to probably give changes like this more karma thresholds. I've released a new update https://bodhi.fedoraproject.org/updates/FEDORA-2025-2f4ba7cd17  that hopefully fixes this. I'll keep an eye on the karma. 

 I had a bug appear in my email recently which led me down a rabbit hole, and I'm going to share it for future people wondering why we can't have nice things. Bug: 1. Get an intel/nvidia (newer than Turing) laptop. 2. Log in to GNOME on Fedora 42/43  3. Hotplug a HDMI port that is connected to the NVIDIA GPU. 4. Desktop stops working. My initial reproduction got me a hung mutter process with a nice backtrace which pointed at the Vulkan Mesa device selection layer, trying to talk to the wayland compositor to ask it what the default device is. The problem was the process was the wayland compositor, and how was this ever supposed to work. The Vulkan device selection was called because zink called EnumeratePhysicalDevices, and zink was being loaded because we recently switched to it as the OpenGL driver for newer NVIDIA GPUs. I looked into zink and the device select layer code, and low and behold someone has hacked around this badly already, and probably wrongly and I've no ide...

AMD have announced the end of the AMDVLK open driver in favour of focusing on radv for Linux use cases. When Bas and I started radv in 2016, AMD were promising their own Linux vulkan driver, which arrived in Dec 2017. At this point radv was already shipping in most Linux distros. AMD strategy of having AMDVLK was developed via over the wall open source releases from internal closed development was always going to be a second place option at that point. When Valve came on board and brought dedicated developer power to radv, and the aco compiler matured, there really was no point putting effort into using AMDVLK which was hard to package and impossible to contribute to meaningfully for external developers. radv is probably my proudest contribution to the Linux ecosystem, finally disproving years of idiots saying an open source driver could never compete with a vendor provided driver, now it is the vendor provided driver. I think we will miss the open source PAL repo as a reference sou...

One of my pet peeves around running local LLMs and inferencing is the sheer mountain of shit^W^W^W complexity of compute stacks needed to run any of this stuff in an mostly optimal way on a piece of hardware. CUDA, ROCm, and Intel oneAPI all to my mind scream over-engineering on a massive scale at least for a single task like inferencing. The combination of closed source, over the wall open source, and open source that is insurmountable for anyone to support or fix outside the vendor, screams that there has to be a simpler way. Combine that with the pytorch ecosystem and insanity of deploying python and I get a bit unstuck. What can be done about it? llama.cpp to me seems like the best answer to the problem at present, (a rust version would be a personal preference, but can't have everything). I like how ramalama wraps llama.cpp to provide a sane container interface, but I'd like to eventually get to the point where container complexity for a GPU compute stack isn't really ...

Blog posts are like buses sometimes... I've spent time over the last month enabling Blackwell support on NVK, the Mesa vulkan driver for NVIDIA GPUs. Faith from Collabora, the NVK maintainer has cleaned up and merged all the major pieces of this work and landed them into mesa this week. Mesa 25.2 should ship with a functioning NVK on blackwell. The code currently in mesa main passes all tests in the Vulkan CTS. Quick summary of the major fun points: Ben @ NVIDIA had done the initial kernel bringup in to r570 firmware in the nouveau driver. I worked with Ben on solidifying that work and ironing out a bunch of memory leaks and regressions that snuck in. Once the kernel was stable, there were a number of differences between Ada and Blackwell that needed to be resolved. Thanks to Faith, Mel and Mohamed for their help, and NVIDIA for providing headers and other info. I did most of the work on a GB203 laptop and a desktop 5080. 1. Instruction encoding: a bunch of instructions changed how...

 I should have mentioned this here a week ago. The Vulkan AV1 encode extension has been out for a while, and I'd done the initial work on enabling it with radv on AMD GPUs. I then left it in a branch, which Benjamin from AMD picked up and fixed a bunch of bugs, and then we both got distracted. I realised when doing VP9 that it hasn't landed, so did a bit of cleanup. Then David from AMD picked it up and carried it over the last mile and it got merged last week. So radv on supported hw now supports all vulkan decode/encode formats currently available.  

The Vulkan WG has released VK_KHR_video_decode_vp9. I did initial work on a Mesa extensions for this a good while back, and I've updated the radv code with help from AMD and Igalia to the final specification. There is an open MR[1] for radv to add support for vp9 decoding on navi10+ with the latest firmware images in linux-firmware. It is currently passing all VK-GL-CTS tests for VP9 decode. Adding this decode extension is a big milestone for me as I think it now covers all the reasons I originally got involved in Vulkan Video as signed off, there is still lots to do and I'll stay involved, but it's been great to see the contributions from others and how there is a bit of Vulkan Video community upstream in Mesa.  [1] https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35398  

There's been a couple of mentions of Rust4Linux in the past week or two, one from Linus on the speed of engagement and one about Wedson departing the project due to non-technical concerns. This got me thinking about project phases and developer types. Archetypes: I will regret making an analogy, in an area I have no experience in, but let's give it a go with a road building analogy.   Let's sort developers into 3 rough categories. Let's preface by saying not all developers fit in a single category throughout their careers, and some developers can do different roles on different projects, or on the same project simultaneously. 1. Wayfinders/Mapmakers I want to go build a hotel somewhere but there exists no map or path. I need to travel through a bunch of mountains, valleys, rivers, weather, animals, friendly humans, antagonistic humans and some unknowns. I don't care deeply about them, I want to make a path to where I want to go. I hit a roadblock, I don't focus...

 Vulkan Video AV1 decode has been released, and I had some partly working support on Intel ANV driver previously, but I let it lapse. The branch is currently [1]. It builds, but is totally untested, I'll get some time next week to plug in my DG2 and see if I can persuade it to decode some frames. Update: the current branch decodes one frame properly, reference frames need more work unfortunately. [1] https://gitlab.freedesktop.org/airlied/mesa/-/commits/anv-vulkan-video-decode-av1

The Khronos Group announced VK_KHR_video_decode_av1 [1], this extension adds AV1 decoding to the Vulkan specification. There is a radv branch [2] and merge request [3]. I did some AV1 work on this in the past, but I need to take some time to see if it has made any progress since. I'll post an ANV update once I figure that out. This extension is one of the ones I've been wanting for a long time, since having royalty-free codec is something I can actually care about and ship, as opposed to the painful ones. I started working on a MESA extension for this a year or so ago with Lynne from the ffmpeg project and we made great progress with it. We submitted that to Khronos and it has gone through the committee process and been refined and validated amongst the hardware vendors. I'd like to say thanks to Charlie Turner and Igalia for taking over a lot of the porting to the Khronos extension and fixing up bugs that their CTS development brought up. This is a great feature of having ...

Vulkan 1.3.274 moves the Vulkan encode work out of BETA and moves h264 and h265 into KHR extensions. radv support for the Vulkan video encode extensions has been in progress for a while. The latest branch is at [1]. This branch has been updated for the new final headers. Updated: It passes all of h265 CTS now, but it is failing one h264 test. Initial ffmpeg support is [2]. [1] https://gitlab.freedesktop.org/airlied/mesa/-/tree/radv-vulkan-video-encode-h2645-spec-latest?ref_type=heads [2] https://github.com/cyanreg/FFmpeg/commits/vulkan/

Linus has pulled the initial GSP firmware support for nouveau. This is just the first set of work to use the new GSP firmware and there are likely many challenges and improvements ahead. To get this working you need to install the firmware which hasn't landed in linux-firmware yet. For Fedora this copr has the firmware in the necessary places: https://copr.fedorainfracloud.org/coprs/airlied/nouveau-gsp/build/6593115/  Hopefully we can upstream that in next week or so. If you have an ADA based GPU then it should just try and work out of the box, if you have Turing or Ampere you currently need to pass nouveau.config=NvGspRm=1 on the kernel command line to attempt to use GSP. Going forward, I've got a few fixes and stabilization bits to land, which we will concentrate on for 6.7, then going forward we have to work out how to keep it up to date and support new hardware and how to add new features.

 Sriram invited me to the oneAPI meetup, and I felt I hadn't summed up the state of compute and community development in a while. Enjoy 45 minutes of opinions! https://www.youtube.com/watch?v=HzzLY5TdnZo

The initial NVK (nouveau vulkan) experimental driver has been merged into mesa master[1], and although there's lots of work to be done before it's application ready, the main reason it was merged was because the initial kernel work needed was merged into drm-misc-next[2] and will then go to drm-next for the 6.6 merge window. (This work is separate from the GSP firmware enablement required for reclocking, that is a parallel development, needed to make nvk useable). Faith at Collabora will have a blog post about the Mesa side, this is more about the kernel journey. What was needed in the kernel? The nouveau kernel API was written 10 years or more ago, and was designed around OpenGL at the time. There were two major restrictions in the current uAPI that made it unsuitable for Vulkan. buffer objects (physical memory allocations) were allocated 1:1 with virtual memory allocations for a file descriptor. This meant the kernel managed the virtual address space. For proper Vulkan suppor...

I recently came across tinygrad as a small powerful nn framework that had an OpenCL backend target and could run LLaMA model. I've been looking out for rusticl workloads, and this seemed like a good one, and I could jump on the AI train, and run an LLM in my house! I started it going on my Radeon 6700XT with the latest rusticl using radeonsi with the LLVM backend, and I could slowly interrogate a model with a question, and it would respond. I've no idea how performant it is vs ROCm yet which seems to be where tinygrad is more directed, but I may get to that next week. While I was there though I decided to give the Mesa ACO compiler backend a go, it's been tied into radeonsi recently, and I done some hacks before to get compute kernels to run. I reproduced said hacks on the modern code and gave it a run. tinygrad comes with a benchmark script called benchmark_train_efficientnet so I started playing with it to see what low hanging fruit I could find in an LLVM vs ACO shootout...

 Thanks for all the suggestions, on here, and on twitter and on mastodon, anyway who noted I could use a single fd and avoid all the pain was correct! I hacked up an ever growing ftruncate/madvise memfd and it seemed to work fine. In order to use it for sparse I have to use it for all device memory allocations in lavapipe which means if I push forward I probably have to prove it works and scales a bit better to myself. I suspect layering some of the pb bufmgr code on top of an ever growing fd might work, or maybe just having multiple 2GB buffers might be enough. Not sure how best to do shaderResourceResidency, userfaultfd might be somewhat useful, mapping with PROT_NONE and then using write(2) to get a -EFAULT is also promising, but I'm not sure how best to avoid segfaults for read/writes to PROT_NONE regions. Once I got that going, though I ran headfirst into something that should have been obvious to me, but I hadn't thought through. llvmpipe allocates all it's textures l...