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[v10,09/13] x86/process: Clear hardware feedback history for AMD processors

Message ID 20250515211950.3102922-10-superm1@kernel.org
State New
Headers show
Series [v10,01/13] Documentation: x86: Add AMD Hardware Feedback Interface documentation | expand

Commit Message

Mario Limonciello May 15, 2025, 9:19 p.m. UTC 
From: Perry Yuan <perry.yuan@amd.com>

Incorporate a mechanism within the context switching code to reset
the hardware history for AMD processors. Specifically, when a task
is switched in, the class ID was read and reset the hardware workload
classification history of CPU firmware and then it start to trigger
workload classification for the next running thread.

Signed-off-by: Perry Yuan <perry.yuan@amd.com>
Co-developed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 arch/x86/kernel/process_64.c | 4 ++++
 1 file changed, 4 insertions(+)
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Patch

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index f39ff02e498d7..3ceb93b784013 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -707,6 +707,10 @@  __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	/* Load the Intel cache allocation PQR MSR. */
 	resctrl_sched_in(next_p);
 
+	/* Reset hw history on AMD CPUs */
+	if (cpu_feature_enabled(X86_FEATURE_AMD_WORKLOAD_CLASS))
+		wrmsrl(AMD_WORKLOAD_HRST, 0x1);
+
 	return prev_p;
 }