The following commit has been merged into the sched/core branch of tip:
Commit-ID: 55409ac5c371c6403012d5f4df5e7c6cf0e7dce6
Gitweb: https://git.kernel.org/tip/55409ac5c371c6403012d5f4df5e7c6cf0e7dce6
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Fri, 22 Oct 2021 17:49:53 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Fri, 22 Oct 2021 18:21:28 +02:00
sched,x86: Fix L2 cache mask
Currently AMD/Hygon do not populate l2c_id, this means that for SMT
enabled systems they report an L2 per thread. This is ofcourse not
true but was harmless so far.
However, since commit: 66558b730f25 ("sched: Add cluster scheduler
level for x86") the scheduler topology setup requires:
SMT <= L2 <= LLC
Which leads to noisy warnings and possibly weird behaviour on affected
chips.
Therefore change the topology generation such that if l2c_id is not
populated it follows the SMT topology, thereby satisfying the
constraint.
Fixes: 66558b730f25 ("sched: Add cluster scheduler level for x86")
Reported-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
arch/x86/kernel/smpboot.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 5094ab0..f80f459 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -470,9 +470,9 @@ static bool match_l2c(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
{
int cpu1 = c->cpu_index, cpu2 = o->cpu_index;
- /* Do not match if we do not have a valid APICID for cpu: */
+ /* If the arch didn't set up l2c_id, fall back to SMT */
if (per_cpu(cpu_l2c_id, cpu1) == BAD_APICID)
- return false;
+ return match_smt(c, o);
/* Do not match if L2 cache id does not match: */
if (per_cpu(cpu_l2c_id, cpu1) != per_cpu(cpu_l2c_id, cpu2))
|