Add new post: AAA gaming on M1!

Signed-off-by: Alyssa Rosenzweig <[email protected]>

Author: alyssarosenzweig

content/blog/2024/10/10-aaa-gaming-on-m1.md

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+date = "2024-10-01T10:00:00-04:00"
+draft = false
+title = "AAA gaming on Asahi Linux"
+slug = "aaa-gaming-on-asahi-linux"
+author = "Alyssa Rosenzweig"
++++
+
+Gaming on Linux on M1 is here! We're thrilled to release our Asahi game playing
+toolkit, which integrates our Vulkan 1.3 drivers with x86 emulation and Windows
+compatibility. Plus a bonus: conformant OpenCL 3.0.
+
+Asahi Linux now ships the only conformant [OpenGL®](https://www.khronos.org/conformance/adopters/conformant-products/opengl#submission_3470),<!--
+[OpenGL® ES](https://www.khronos.org/conformance/adopters/conformant-products/opengles#submission_1045),-->
+[OpenCL™](https://www.khronos.org/conformance/adopters/conformant-products/opencl#submission_433), and
+[Vulkan®](https://www.khronos.org/conformance/adopters/conformant-products#submission_7910)
+drivers for this hardware. As for gaming... while today's release is an alpha, [**Control**](https://store.steampowered.com/app/870780/Control_Ultimate_Edition/) runs well!
+
+<figure><a href="/img/blog/2024/10/Control-small.png"><img src="/img/blog/2024/10/Control-small.avif" alt="Control"></a></figure>
+
+## Installation
+
+First, install [Fedora Asahi Remix](https://asahilinux.org/fedora/). Once
+installed, get the latest drivers with <code style="white-space:nowrap">dnf
+upgrade \-\-refresh && reboot</code>. Then just <code
+style="white-space:nowrap">dnf install steam</code> and play. While all M1/M2-series systems work, most games require 16GB of memory due to emulation overhead.
+
+## The stack
+
+Games are typically x86 Windows binaries rendering with DirectX, while our target is Arm Linux
+with Vulkan. We need to handle each difference:
+
+* [FEX](https://fex-emu.com/) emulates x86 on Arm.
+* [Wine](https://www.winehq.org/) translates Windows to Linux.
+* [DXVK](https://github.com/doitsujin/dxvk) and [vkd3d-proton](https://github.com/HansKristian-Work/vkd3d-proton) translate DirectX to Vulkan.
+
+There's one curveball: page size. Operating systems allocate memory in fixed
+size "pages". If an application expects smaller pages than the system uses,
+they will break due to insufficient alignment of allocations. That's a problem:
+x86 expects 4K pages but Apple systems use 16K pages.
+
+While Linux can't mix page sizes between processes, it *can* virtualize another
+Arm Linux kernel with a different page size. So we run games inside a tiny
+virtual machine using [muvm](https://github.com/AsahiLinux/muvm), passing through
+devices like the GPU and game controllers. The
+hardware is happy because the system is 16K, the game is happy because the
+virtual machine is 4K, and you're happy because you can play [**Fallout
+4**](https://store.steampowered.com/app/377160/Fallout_4/).
+
+<figure><a href="/img/blog/2024/10/Fallout4-small.png"><img src="/img/blog/2024/10/Fallout4-small.avif" alt="Fallout 4"></a></figure>
+
+## Vulkan
+
+The final piece is an adult-level Vulkan driver, since translating DirectX requires Vulkan 1.3
+with many extensions. Back in April, I wrote
+[Honeykrisp](https://rosenzweig.io/blog/vk13-on-the-m1-in-1-month.html), the
+only Vulkan 1.3 driver for Apple hardware. I've since added DXVK support. Let's look at some new features.
+
+### Tessellation
+
+Tessellation enables games like [**The Witcher 3**](https://store.steampowered.com/app/292030/The_Witcher_3_Wild_Hunt/) to generate
+geometry. The M1 has hardware tessellation, but it is
+too limited for DirectX, Vulkan, or OpenGL. We must instead tessellate with arcane compute shaders, as detailed in [today's talk at XDC2024](https://www.youtube.com/live/pDsksRBLXPk).
+
+<figure><a href="/img/blog/2024/10/Witcher3-small.png"><img src="/img/blog/2024/10/Witcher3-small.avif" alt="The Witcher 3"></a></figure>
+
+### Geometry shaders
+
+Geometry shaders are an older, cruder method to generate geometry.  Like
+tessellation, the M1 lacks geometry shader hardware so we emulate with compute.
+Is that fast? No, but geometry shaders are slow [even on desktop
+GPUs](http://www.joshbarczak.com/blog/?p=667). They don't need to be fast --
+just fast enough for games like
+[**Ghostrunner**](https://store.steampowered.com/app/1139900/Ghostrunner/).
+
+<figure><a href="/img/blog/2024/10/Ghostrunner-small.png"><img src="/img/blog/2024/10/Ghostrunner-small.avif" alt="Ghostrunner"></a></figure>
+
+### Enhanced robustness
+
+"Robustness" permits an application's shaders to access buffers out-of-bounds
+without crashing the hardware. In OpenGL and Vulkan, out-of-bounds loads may
+return arbitrary elements, and out-of-bounds stores may corrupt the buffer.
+Our OpenGL driver [exploits this
+definition](https://rosenzweig.io/blog/conformant-gl46-on-the-m1.html) for
+efficient robustness on the M1.
+
+Some games require stronger guarantees.  In DirectX, out-of-bounds loads return zero, and
+out-of-bounds stores are ignored. DXVK therefore requires
+[`VK_EXT_robustness2`](https://docs.vulkan.org/guide/latest/robustness.html#_vk_ext_robustness2),
+a Vulkan extension strengthening robustness.
+
+Like before, we implement robustness with compare-and-select instructions. A
+naïve implementation would *compare* a loaded index with the buffer size and
+*select* a zero result if out-of-bounds. However, our GPU loads are vector
+while arithmetic is scalar. Even if we disabled page faults, we would need up
+to four compare-and-selects per load.
+
+```asm
+load R, buffer, index * 16
+ulesel R[0], index, size, R[0], 0
+ulesel R[1], index, size, R[1], 0
+ulesel R[2], index, size, R[2], 0
+ulesel R[3], index, size, R[3], 0
+```
+
+There's a trick: reserve *64 gigabytes* of zeroes using virtual memory voodoo.
+Since every 32-bit index multiplied by 16 fits in 64 gigabytes, any index into
+this region loads zeroes. For out-of-bounds loads, we simply replace the buffer
+address with the reserved address while preserving the index. Replacing a
+64-bit address costs just two 32-bit compare-and-selects.
+
+```asm
+ulesel buffer.lo, index, size, buffer.lo, RESERVED.lo
+ulesel buffer.hi, index, size, buffer.hi, RESERVED.hi
+load R, buffer, index * 16
+```
+
+Two instructions, not four.
+
+## Next steps
+
+Sparse texturing is next for Honeykrisp, which will unlock more DX12 games. The alpha already runs DX12 games that don't require sparse, like [**Cyberpunk
+2077**](https://store.steampowered.com/app/1091500/Cyberpunk_2077/).
+
+<figure><a href="/img/blog/2024/10/Cyberpunk2077-small.png"><img src="/img/blog/2024/10/Cyberpunk2077-small.avif" alt="Cyberpunk 2077"></a></figure>
+
+While many games are playable, newer AAA titles don't hit 60fps *yet*.
+Correctness comes first. Performance improves next. Indie games like
+[**Hollow Knight**](https://store.steampowered.com/app/367520/Hollow_Knight/) do run full speed.
+
+<figure><a href="/img/blog/2024/10/HollowKnight-small.png"><img src="/img/blog/2024/10/HollowKnight-small.avif" alt="Hollow Knight"></a></figure>
+
+Beyond gaming, we're adding general purpose x86 emulation based on this
+stack. For more information, [see the
+FAQ](https://docs.fedoraproject.org/en-US/fedora-asahi-remix/x86-support/).
+
+Today's alpha is a taste of what's to come. Not the final form, but
+enough to enjoy [**Portal 2**](https://store.steampowered.com/app/620/Portal_2/) while we work towards "1.0".
+
+<figure><a href="/img/blog/2024/10/Portal2-small.png"><img src="/img/blog/2024/10/Portal2-small.avif" alt="Portal 2"></a></figure>
+
+## Acknowledgements
+
+This work has been years in the making with major contributions from...
+
+* [Alyssa Rosenzweig](https://rosenzweig.io)
+* [Asahi Lina](https://lina.yt/me)
+* [chaos_princess](https://social.treehouse.systems/@chaos_princess)
+* [Davide Cavalca](https://github.com/davide125)
+* [Dougall Johnson](https://mastodon.social/@dougall)
+* [Ella Stanforth](https://ella.gay)
+* [Faith Ekstrand](https://www.gfxstrand.net/faith/welcome/)
+* [Janne Grunau](https://social.treehouse.systems/@janne)
+* [Karol Herbst](https://chaos.social/@karolherbst)
+* [marcan](https://social.treehouse.systems/@marcan)
+* [Mary Guillemard](https://mary.zone)
+* [Neal Gompa](https://neal.gompa.dev/)
+* [Sergio López](https://sinrega.org)
+* [TellowKrinkle](https://github.com/TellowKrinkle)
+* [Teoh Han Hui](https://github.com/teohhanhui)
+* [Rob Clark](https://mastodon.gamedev.place/@robclark)
+* [Ryan Houdek](https://github.com/sonicadvance1)
+
+... Plus hundreds of developers whose work we build upon, spanning the Linux,
+Mesa, Wine, and FEX projects. Today's release is
+thanks to the magic of open source.
+
+We hope you enjoy the magic.
+
+Happy gaming.