linux-kernel - [PATCH v5 2/2] misc: pvpanic: introduce events device attribue

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Date:   Sun, 10 Jan 2021 19:53:58 +0800
From:   zhenwei pi <pizhenwei@...edance.com>
To:     arnd@...db.de, gregkh@...uxfoundation.org
Cc:     pbonzini@...hat.com, linux-kernel@...r.kernel.org,
        pizhenwei@...edance.com
Subject: [PATCH v5 2/2] misc: pvpanic: introduce events device attribue

Suggested by Paolo & Greg, add 'events' device attribute that can be
used to limit which capabilities the driver uses.

Finally, the pvpanic guest driver works by the limitation of both
device capability and user setting.

Signed-off-by: zhenwei pi <pizhenwei@...edance.com>
---
 .../ABI/testing/sysfs-bus-pci-devices-pvpanic | 12 ++++++++
 drivers/misc/pvpanic.c                        | 30 ++++++++++++++++++-
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-pci-devices-pvpanic b/Documentation/ABI/testing/sysfs-bus-pci-devices-pvpanic
index 79b7dc31cd55..1936f7324155 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci-devices-pvpanic
+++ b/Documentation/ABI/testing/sysfs-bus-pci-devices-pvpanic
@@ -10,3 +10,15 @@ Description:
 		Detailed bit definition refers to section <Bit Definition>
 		from pvpanic device specification:
 		https://git.qemu.org/?p=qemu.git;a=blob_plain;f=docs/specs/pvpanic.txt
+
+What:		/sys/devices/pci0000:00/*/QEMU0001:00/events
+Date:		Jan 2021
+Contact:	zhenwei pi <pizhenwei@...edance.com>
+Description:
+		RW attribute. Set/get which features in-use. This attribute
+		is used to enable/disable feature(s) of pvpanic device.
+		Notice that this value should be a subset of capability.
+
+		Format: %x.
+
+		Also refer to pvpanic device specification.
diff --git a/drivers/misc/pvpanic.c b/drivers/misc/pvpanic.c
index 7e5254e8af1f..a9ac26c7b11f 100644
--- a/drivers/misc/pvpanic.c
+++ b/drivers/misc/pvpanic.c
@@ -20,6 +20,7 @@
 
 static void __iomem *base;
 static unsigned int capability = PVPANIC_PANICKED | PVPANIC_CRASH_LOADED;
+static unsigned int events;
 
 static ssize_t capability_show(struct device *dev,
 			       struct device_attribute *attr, char *buf)
@@ -28,8 +29,34 @@ static ssize_t capability_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(capability);
 
+static ssize_t events_show(struct device *dev,  struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%x", events);
+}
+
+static ssize_t events_store(struct device *dev,  struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	unsigned int tmp;
+	int err;
+
+	err = kstrtouint(buf, 16, &tmp);
+	if (err)
+		return err;
+
+	if ((tmp & capability) != tmp)
+		return -EINVAL;
+
+	events = tmp;
+
+	return count;
+
+}
+static DEVICE_ATTR_RW(events);
+
 static struct attribute *pvpanic_dev_attrs[] = {
 	&dev_attr_capability.attr,
+	&dev_attr_events.attr,
 	NULL
 };
 ATTRIBUTE_GROUPS(pvpanic_dev);
@@ -41,7 +68,7 @@ MODULE_LICENSE("GPL");
 static void
 pvpanic_send_event(unsigned int event)
 {
-	if (event & capability)
+	if (event & capability & events)
 		iowrite8(event, base);
 }
 
@@ -79,6 +106,7 @@ static int pvpanic_mmio_probe(struct platform_device *pdev)
 
 	/* initlize capability by RDPT */
 	capability &= ioread8(base);
+	events = capability;
 
 	if (capability)
 		atomic_notifier_chain_register(&panic_notifier_list,
-- 
2.25.1