[PATCH v6 00/19] ARM64 PMU Partitioning

[Colton Lewis]

Marc Zyngier <maz at kernel.org> writes:

> On Thu, 12 Feb 2026 21:08:36 +0000,
> Colton Lewis <coltonlewis at google.com> wrote:

>> Hey Marc, thanks for the review.

>> Marc Zyngier <maz at kernel.org> writes:

>> > On Mon, 09 Feb 2026 22:13:55 +0000,
>> > Colton Lewis <coltonlewis at google.com> wrote:

>> >> This series creates a new PMU scheme on ARM, a partitioned PMU that
>> >> allows reserving a subset of counters for more direct guest access,
>> >> significantly reducing overhead. More details, including performance
>> >> benchmarks, can be read in the v1 cover letter linked below.

>> >> An overview of what this series accomplishes was presented at KVM
>> >> Forum 2025. Slides [1] and video [2] are linked below.

>> >> IMPORTANT: This iteration does not yet implement the dynamic counter
>> >> reservation approach suggested by Will Deacon in January [3]. I am
>> >> working on it, but wanted to send this version first to keep momentum
>> >> going and ensure I've addressed all issues besides that.

>> > [...]

>> > As I have asked before, this is missing an example of how userspace is
>> > going to use this. Without it, it is impossible to correctly review
>> > this series.

>> > Please consider this as a blocker.

>> Understood. I remember you asking for a QEMU patch specifically.

> No. *any* VMM. QEMU, kvmtool, crosvm, firecrackpoter, whichever you want.

>> I had hoped that the use in the selftest was sufficient to show how to
>> use the uAPI.

> The selftests are absolutely pointless, like 99% of all selftests.
> They don't demonstrate how the userspace API works, now how
> configuring the PMU is ordered with the rest of the save/restore flow.

>> If not, I can send out an example QEMU patch to the QEMU ARM mailing
>> list.

Okay I sent one to you, qemu-arm, and everyone else I asked to review
this series.