Linux 4.15 Is A Huge Update For Both AMD CPU & Radeon GPU Owners

Linux 4.15 is shaping up to be a massive kernel release and we are just half-way through its merge window period. But for AMD Linux users especially, the 4.15 kernel release is going to be rocking.

Whether you are using AMD processors and/or AMD Radeon graphics cards, Linux 4.15 is a terrific way to end of the year. There are a number of improvements to make this release great for AMD customers.

First and foremost, AMDGPU DC was merged Friday night. This addition of over 130,000 lines of code to the kernel provides Radeon RX Vega display support, the initial Raven Ridge APU display support, HDMI/DP audio for recent generations of Radeon hardware, atomic mode-setting, initial FreeSync prep support, and other modern display features that takes it close to parity with the Radeon Software Windows driver. It was a long time coming and finally happened for Linux 4.15. See my dozens of AMDGPU DC articles for more on the topic.

In addition to AMDGPU DC display code landing, there is AMDGPU priority scheduling support as developed by Valve for ensuring Steam VR on Linux can run at a higher priority to reduce the risk of slowdowns causing motion sickness and the like. This priority scheduler was in development for a year and finally landed. For the RADV Vulkan driver this support is exposed via VK_EXT_global_priority extension in Git for Mesa 17.3. I hope to find the time in the days ahead to deliver some fresh Steam VR Linux testing with the HTC Vive on different graphics cards / drivers.

Other AMDGPU DRM work that's found in Linux 4.15 includes GPU reset support for RX Vega graphics cards in the event of hangs or other issues, GCN 1.1 Sea Islands PowerPlay support, TTM memory management updates, PRIME mmap support, more prep work for Raven Ridge APUs, and other improvements.

There's also much to be thankful for if you are running a new AMD CPU... Benefiting all AMD Zen CPUs whether it be Ryzen, Threadripper, or EPYC, there is finally AMD Zen CPU temperature monitoring support that's extended within the k10temp hwmon driver. It's silly it has taken so long, but with Linux 4.15 you can now read the CPU package temperatures of these new AMD processors under Linux.

The Linux 4.15 PCI improvements include 64-bit BAR support for AMD Family 15h (Bulldozer) processors.

Exciting for the EPYC server processors after Secure Memory Encryption (SME) landed in Linux 4.14 is taking it further now with SEV. Secure Encrypted Virtualization landed in Linux 4.15 for allowing guest VMs to have their memory encrypted by the hardware whereby only the guest VM can view the unencrypted data -- protecting against any rogue processes on the host trying to view a VM's memory, a fellow VM trying to exploit memory access to another VM, etc.

Also benefiting AMD EPYC customers with Linux 4.15 is improved scheduler behavior for EPYC with regard to better balancing of NUMA nodes.

The merge window for Linux 4.15 will end next weekend (26 November) while the official stable release of it should be out ~8 weeks later; roughly putting the stable Linux 4.15 release around the middle of January. Linux 4.15 is what's tentatively slated as the default kernel for Ubuntu 18.04 LTS, among other distribution releases in H1'2018. But, of course, nothing is stopping you from building this kernel yourself in its latest daily/Git state if you want these features now.

If I have missed any other interesting AMD/Radeon changes for Linux 4.15 so far, feel free to point out in the forums. Of course, our monitoring of Linux 4.15's development in general will continue as well as our benchmarking of this kernel in the days ahead.

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