Re: [PATCH v2 3/3] RISC-V: hwprobe: not treat KEY_CPUPERF_0 as bitmask

From: Palmer Dabbelt
Date: Wed Jun 26 2024 - 10:44:53 EST


On Wed, 29 May 2024 11:33:42 PDT (-0700), Evan Green wrote:
On Thu, May 23, 2024 at 8:36 PM Yangyu Chen <cyy@xxxxxxxxxxxx> wrote:

Since the value in KEY_CPUPERF_0 is not bitmask, remove the wrong code
in hwprobe.h.

Signed-off-by: Yangyu Chen <cyy@xxxxxxxxxxxx>

I'd expect a Fixes tag, and ideally some discussion on the reasoning
and ramifications of this change.

I posted the other possible fix, declaring a new key, at [1], mostly
so we could see the two options and discuss. I'm okay with either
patch.

Just to close the loop here as the discussions are on other threads: after a bunch of discussions we're going with the new key version. Maybe it's a bit pedantic, but since hwprobe is such a fundamental compatibility interface we're just going to be super careful.

-Evan

[1] https://lore.kernel.org/lkml/20240529182649.2635123-1-evan@xxxxxxxxxxxx/T/#u

---
arch/riscv/include/asm/hwprobe.h | 1 -
1 file changed, 1 deletion(-)

diff --git a/arch/riscv/include/asm/hwprobe.h b/arch/riscv/include/asm/hwprobe.h
index 630507dff5ea..f24cad22bbe1 100644
--- a/arch/riscv/include/asm/hwprobe.h
+++ b/arch/riscv/include/asm/hwprobe.h
@@ -20,7 +20,6 @@ static inline bool hwprobe_key_is_bitmask(__s64 key)
switch (key) {
case RISCV_HWPROBE_KEY_BASE_BEHAVIOR:
case RISCV_HWPROBE_KEY_IMA_EXT_0:
- case RISCV_HWPROBE_KEY_CPUPERF_0:
return true;
}

--
2.45.1