linux-kernel - [PATCH 1/4] hwtracing: hisi_ptt: Make cpumask only present online CPUs

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Date:   Wed, 15 Mar 2023 17:43:13 +0800
From:   Yicong Yang <yangyicong@...wei.com>
To:     <mathieu.poirier@...aro.org>, <suzuki.poulose@....com>,
        <jonathan.cameron@...wei.com>, <corbet@....net>,
        <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>
CC:     <alexander.shishkin@...ux.intel.com>, <helgaas@...nel.org>,
        <linux-pci@...r.kernel.org>, <prime.zeng@...wei.com>,
        <linuxarm@...wei.com>
Subject: [PATCH 1/4] hwtracing: hisi_ptt: Make cpumask only present online CPUs

From: Yicong Yang <yangyicong@...ilicon.com>

perf will try to start PTT trace on every CPU presented in cpumask sysfs
attribute and it will fail to start on offline CPUs(see the comments in
perf_event_open()). But the driver is using cpumask_of_node() to export
the available cpumask which may include offline CPUs and may fail the
perf unintendedly. Fix this by only export the online CPUs of the node.

Fixes: ff0de066b463 ("hwtracing: hisi_ptt: Add trace function support for HiSilicon PCIe Tune and Trace device")
Signed-off-by: Yicong Yang <yangyicong@...ilicon.com>
---
 drivers/hwtracing/ptt/hisi_ptt.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/ptt/hisi_ptt.c b/drivers/hwtracing/ptt/hisi_ptt.c
index 30f1525639b5..0a10c7ec46ad 100644
--- a/drivers/hwtracing/ptt/hisi_ptt.c
+++ b/drivers/hwtracing/ptt/hisi_ptt.c
@@ -487,9 +487,18 @@ static ssize_t cpumask_show(struct device *dev, struct device_attribute *attr,
 			    char *buf)
 {
 	struct hisi_ptt *hisi_ptt = to_hisi_ptt(dev_get_drvdata(dev));
-	const cpumask_t *cpumask = cpumask_of_node(dev_to_node(&hisi_ptt->pdev->dev));
+	cpumask_var_t mask;
+	ssize_t n;
 
-	return cpumap_print_to_pagebuf(true, buf, cpumask);
+	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
+		return 0;
+
+	cpumask_and(mask, cpumask_of_node(dev_to_node(&hisi_ptt->pdev->dev)),
+		    cpu_online_mask);
+	n = cpumap_print_to_pagebuf(true, buf, mask);
+	free_cpumask_var(mask);
+
+	return n;
 }
 static DEVICE_ATTR_RO(cpumask);
 
-- 
2.24.0