Linux 6.19 Overhauling The Intel TDX Locking Code For KVM

Sean Christopherson of Google sent out the pull requests to the KVM tree of the various x86_64-related areas of virtualization he oversees. With these updates ahead of the Linux 6.19 merge window there is a significant overhaul of Intel's Trust Domain Extensions (TDX) code to address various outstanding problems.

The KVM x86 TDX pull of new material for Linux 6.19 includes "a large overhaul of lock-related TDX code" for dealing with various locking contention issues with that Intel confidential computing security feature for VMs.

Christopherson explained of the TDX overhaul in the pull request:

"Overhaul the TDX code to address systemic races where KVM (acting on behalf of userspace) could inadvertantly trigger lock contention in the TDX-Module, which KVM was either working around in weird, ugly ways, or was simply oblivious to (as proven by Yan tripping several KVM_BUG_ON()s with clever selftests)."

That is part of this TDX pull ahead of the Linux 6.19 merge window opening in early December.

Sean also sent out the queued AMD SVM changes too for KVM. That pull includes various minor fixes, AVIC support for addressing 4K vCPUs in x2AVIC mode, and other small changes but seemingly nothing too exciting this round.

Another pull for the KVM x86 code does add NUMA mempolicy support for guest_memfd that may be of interest to some users.