Re: [PATCH] x86/perf: Fixed kernel panic during boot on Nano processor.

From: Codyyao-oc
Date: Wed Jun 30 2021 - 00:38:37 EST


Dear Mingo and Peter,

Thank you for taking your precious time to read this letter, I am very graterful.


Last month, I fixed the bug that boot failed on Nano processor which introduced by

"Fixes: 3a4ac121c2ca ("x86/perf: Add hardware performance events support for Zhaoxin CPU.")"

with Arjan's help and submitted this patch.  But I haven't got back. Greatly appreciate if you could kindly

check it and reply at your convenience.

Many Thanks!

Cody

On 2021/6/7 上午9:31, Cody Yao-oc wrote:
From: CodyYao-oc <CodyYao-oc@xxxxxxxxxxx>

Nano processor may not fully support rdpmc instruction, it works well
for reading general pmc counter, but will lead to GP(general protection)
when accessing fixed pmc counter. Futhermore, family/model information
is same between Nano processor and ZX-C processor, it leads to zhaoxin
pmu driver is wrongly loaded for Nano processor, which resulting boot
kernal fail.

To solve this problem, stepping information will be checked to distinguish
between Nano processor and ZX-C processor.

[https://bugzilla.kernel.org/show_bug.cgi?id=212389]

Reported-by: Arjan <8vvbbqzo567a@xxxxxxxxxxxxxxxxx>
Signed-off-by: CodyYao-oc <CodyYao-oc@xxxxxxxxxxx>
---
arch/x86/events/zhaoxin/core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/zhaoxin/core.c b/arch/x86/events/zhaoxin/core.c
index 949d845c922b..cef1de251613 100644
--- a/arch/x86/events/zhaoxin/core.c
+++ b/arch/x86/events/zhaoxin/core.c
@@ -541,7 +541,8 @@ __init int zhaoxin_pmu_init(void)
switch (boot_cpu_data.x86) {
case 0x06:
- if (boot_cpu_data.x86_model == 0x0f || boot_cpu_data.x86_model == 0x19) {
+ if ((boot_cpu_data.x86_model == 0x0f && boot_cpu_data.x86_stepping >= 0x0e) ||
+ boot_cpu_data.x86_model == 0x19) {
x86_pmu.max_period = x86_pmu.cntval_mask >> 1;