Re: [PATCH 6.6.y] perf/x86/intel: Fix ARCH_PERFMON_NUM_COUNTER_LEAF

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Feb 20, 2025 at 08:31:46AM -0800, Kan Liang wrote:
> The EAX of the CPUID Leaf 023H enumerates the mask of valid sub-leaves.
> To tell the availability of the sub-leaf 1 (enumerate the counter mask),
> perf should check the bit 1 (0x2) of EAS, rather than bit 0 (0x1).
> 
> The error is not user-visible on bare metal. Because the sub-leaf 0 and
> the sub-leaf 1 are always available. However, it may bring issues in a
> virtualization environment when a VMM only enumerates the sub-leaf 0.
> 
> Introduce the cpuid35_e?x to replace the macros, which makes the
> implementation style consistent.
> 
> Fixes: eb467aaac21e ("perf/x86/intel: Support Architectural PerfMon Extension leaf")
> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Cc: stable@vger.kernel.org
> Link: https://lkml.kernel.org/r/20250129154820.3755948-3-kan.liang@linux.intel.com
> ---
>  arch/x86/events/intel/core.c      | 17 ++++++++++-------
>  arch/x86/include/asm/perf_event.h | 26 +++++++++++++++++++++++++-
>  2 files changed, 35 insertions(+), 8 deletions(-)


<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>