Intel AMX Support For KVM Use May Be Ready For Mainline

Written by Michael Larabel in Intel on 6 January 2022 at 05:02 AM EST. Add A Comment
In preparation for Xeon Scalable "Sapphire Rapids" processors, Linux 5.16 adds support for Advanced Matrix Extensions. But that AMX bring-up is more invasive than when introducing AVX as with AMX the feature needs to be "requested" for use by user-space, among other changes. As such extra handling also needed to be introduced for the Kernel-based Virtual Machine (KVM) that hadn't made it for v5.16 but now it looks like the AMX KVM support may be ready for mainline.

After getting the main AMX enablement code ready and merged for the Linux kernel, Intel engineers moved on to AMX support for KVM guests. The KVM changes are more involved than when bringing up AVX but now in having spun five rounds of patches, the Intel engineers believe this support is also ready for mainline.

Intel's Yang Zhon sent out the 21 patches making up the "v5" support for AMX in KVM. He kicked off that round this week with, "Thanks a lot for all the review comments and guidance! Hope this version is in a good state now. :)"

The AMX KVM v5 patches have various code fixes and improvements, addressing feedback from prior rounds of review. It's looking like things are buttoned up that AMX KVM support may be ready for mainlining if the KVM maintainer agrees. We'll see if it still can squeeze into the imminent v5.17 merge window or will be held off until v5.18, stay tuned. Given many public cloud providers today relying on KVM, these patches will be important for next-generation VMs using Sapphire Rapids in order to enjoy AMX.

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