linux-kernel - [RFC PATCH 03/41] perf: Set exclude_guest onto nmi

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Date: Fri, 26 Jan 2024 16:54:06 +0800
From: Xiong Zhang <xiong.y.zhang@...ux.intel.com>
To: seanjc@...gle.com,
	pbonzini@...hat.com,
	peterz@...radead.org,
	mizhang@...gle.com,
	kan.liang@...el.com,
	zhenyuw@...ux.intel.com,
	dapeng1.mi@...ux.intel.com,
	jmattson@...gle.com
Cc: kvm@...r.kernel.org,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	zhiyuan.lv@...el.com,
	eranian@...gle.com,
	irogers@...gle.com,
	samantha.alt@...el.com,
	like.xu.linux@...il.com,
	chao.gao@...el.com,
	xiong.y.zhang@...ux.intel.com,
	Xiong Zhang <xiong.y.zhang@...el.com>
Subject: [RFC PATCH 03/41] perf: Set exclude_guest onto nmi_watchdog

From: Xiong Zhang <xiong.y.zhang@...el.com>

The perf event for NMI watchdog is per cpu pinned system wide event,
if such event doesn't have exclude_guest flag, it will be put into
error state once guest with passthrough PMU starts, this breaks
NMI watchdog function totally.

This commit adds exclude_guest flag for this perf event, so this perf
event is stopped during VM running, but it will continue working after
VM exit. In this way the NMI watchdog can not detect hardlockups during
VM running, it still breaks NMI watchdog function a bit. But host perf
event must be stopped during VM with passthrough PMU running, current
no other reliable method can be used to replace perf event for NMI
watchdog.

Signed-off-by: Xiong Zhang <xiong.y.zhang@...el.com>
Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
---
 kernel/watchdog_perf.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/watchdog_perf.c b/kernel/watchdog_perf.c
index 8ea00c4a24b2..c8ba656ff674 100644
--- a/kernel/watchdog_perf.c
+++ b/kernel/watchdog_perf.c
@@ -88,6 +88,7 @@ static struct perf_event_attr wd_hw_attr = {
 	.size		= sizeof(struct perf_event_attr),
 	.pinned		= 1,
 	.disabled	= 1,
+	.exclude_guest  = 1,
 };

 /* Callback function for perf event subsystem */
-- 
2.34.1