libpmc: Query hwpmc for caps

This change allows for fine-grained capabilities per counter index. This
is particularly useful for AMD where subclasses are not exposed to the
general PMC code, but other architectures also have asymmetric behaviors
when it comes to specific counter indices.

A new PMC_OP_GETCAPS op is added to the hwpmc(4) ioctl interface.

Reviewed by:	mhorne
Sponsored by:	Netflix
Pull Request:	https://github.com/freebsd/freebsd-src/pull/2058

This commit is contained in:

Ali Mashtizadeh

2026-03-01 22:08:30 +00:00

committed by

Mitchell Horne

parent f0e0c4c529

commit 44a983d249

5 changed files with 87 additions and 11 deletions

share/man/man4/hwpmc.4

View File

@@ -325,6 +325,10 @@ This operation returns to the caller after the write operation
 has returned.
 The returned error code reflects any pending error state inside
 .Nm .
 .It Dv PMC_OP_GETCAPS
 Retrieve the capabilities associated with a specific PMC counter.
 Some capabilities may be limited to specific indices (i.e., not available
 across all counters within a class).
 .It Dv PMC_OP_GETCPUINFO
 Retrieve information about the highest possible CPU number for the system,
 and the number of hardware performance monitoring counters available per CPU.