x86/mm/tlb: Add tracepoint for TLB flush IPI to stale CPU

Add a tracepoint when we send a TLB flush IPI to a CPU that used to be in the mm_cpumask, but isn't any more. Suggested-by: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Rik van Riel <riel@surriel.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20241114152723.1294686-3-riel@surriel.com
mariux64 · Nov 19, 2024 · 2815a56 · 2815a56
1 parent 209954c
commit 2815a56
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diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
@@ -760,6 +760,7 @@ static void flush_tlb_func(void *info)
 		/* Can only happen on remote CPUs */
 		if (f->mm && f->mm != loaded_mm) {
 			cpumask_clear_cpu(raw_smp_processor_id(), mm_cpumask(f->mm));
+			trace_tlb_flush(TLB_REMOTE_WRONG_CPU, 0);
 			return;
 		}
 	}

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
@@ -1335,6 +1335,7 @@ enum tlb_flush_reason {
 	TLB_LOCAL_SHOOTDOWN,
 	TLB_LOCAL_MM_SHOOTDOWN,
 	TLB_REMOTE_SEND_IPI,
+	TLB_REMOTE_WRONG_CPU,
 	NR_TLB_FLUSH_REASONS,
 };