[LSF/MM/BPF TOPIC] Implementing KVM vCPU Priority boosting via BPF

From: Joel Fernandes <joel@joelfernandes.org>
To: bpf@vger.kernel.org, lsf-pc@lists.linux-foundation.org,
	David Vernet <void@manifault.com>,
	Sean Christopherson <seanjc@google.com>,
	Vineeth Pillai <vineethrp@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Suleiman Souhlal <suleiman@google.com>
Subject: [LSF/MM/BPF TOPIC] Implementing KVM vCPU Priority boosting via BPF
Date: Tue, 23 Jan 2024 21:59:50 -0500	[thread overview]
Message-ID: <653c2448-614e-48d6-af31-c5920d688f3e@joelfernandes.org> (raw)

We should discuss a new approach for increasing KVM virtual CPU (vCPU) priority
when guests need low latency. The last RFC posting [1] on this is thought to be
too rigid and baking too much policy into the kernel. Incorporating complex
policy logic directly into KVM seems problematic long-term for maintenance. Lets
discuss leveraging BPF programs to offload more scheduling policy decisions to
BPF / userspace.

Specific issues to discuss:

* Add support for enabling BPF programs to share memory and interface with guest.

* Create a kernel function allowing BPF programs to call sched_setscheduler(),
facilitating priority boosting.

* UAPI concerns.

* Challenges with loading BPF programs in guest userspace we don't control.

[1] https://lore.kernel.org/all/20231214024727.3503870-1-vineeth@bitbyteword.org/