Re: [PATCH v2] riscv: perf: Drop defining `perf_instruction_pointer()` and `perf_misc_flags()`

[Ingo Molnar]

* Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx> wrote:

> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> 
> With commit 2c47e7a74f44 ("perf/core: Correct perf sampling with guest
> VMs"), the perf core now handles the functionality previously requiring
> arch-specific definitions of `perf_instruction_pointer()` and
> `perf_misc_flags()`. As these definitions are no longer necessary for
> RISC-V, this patch removes their implementation and declarations.
> 
> This change also fixes the following build issue on RISC-V:
> 
>     ./include/linux/perf_event.h:1679:84: error: macro "perf_misc_flags" passed 2 arguments, but takes just 1
>     ./include/linux/perf_event.h:1679:22: error: 'perf_misc_flags' redeclared as different kind of symbol
>     ./include/linux/perf_event.h:1680:22: error: conflicting types for 'perf_instruction_pointer'; have 'long unsigned int(struct perf_event *, struct pt_regs *)'
> 
> The above errors arise from conflicts between the core definitions in
> `linux/perf_event.h` and the RISC-V-specific definitions in
> `arch/riscv/include/asm/perf_event.h`. Removing the RISC-V-specific
> definitions resolves these issues and aligns the architecture with the
> updated perf core.
> 
> Fixes: 2c47e7a74f44 ("perf/core: Correct perf sampling with guest VMs")

Yeah, so the Fixes tag is wrong - this is not a build bug
with that commit, and your patch does not even apply to
the perf events tree.

This is a semantic merge conflict that arises in linux-next - the
riscv version of perf_instruction_pointer() function doesn't even
exist in the perf tree...

AFAICS the problem is that the riscv tree applied this commit:

  5bb5ccb3e8d8 ("riscv: perf: add guest vs host distinction")

While the perf tree solved this in a more generic fashion:

  2c47e7a74f44 perf/core: Correct perf sampling with guest VMs
  baff01f3d75f perf/x86: Refactor misc flag assignments
  3e807cf07d96 perf/powerpc: Use perf_arch_instruction_pointer()
  04782e63917d perf/core: Hoist perf_instruction_pointer() and perf_misc_flags()
  e33ed362cf9e perf/arm: Drop unused functions

So I believe, assuming the perf version works fine on riscv
(I haven't tested it), that the solution is to revert
5bb5ccb3e8d8 either in the riscv tree, or upon merging it.

Thanks,

	Ingo