cxl/mem: Add debugfs attributes for poison inject and clear

Inject and Clear Poison commands are optionally supported by CXL
memdev devices and are intended for use in debug environments only.
Add debugfs attributes for user access.

Documentation/ABI/testing/debugfs-cxl describes the usage.

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/0c9ea8e671b8e58465d18722788b60d325c675c7.1681874357.git.alison.schofield@intel.com
Tested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Author: AlisonSchofield

Documentation/ABI/testing/debugfs-cxl

@@ -0,0 +1,35 @@
+What:		/sys/kernel/debug/cxl/memX/inject_poison
+Date:		April, 2023
+KernelVersion:	v6.4
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		(WO) When a Device Physical Address (DPA) is written to this
+		attribute, the memdev driver sends an inject poison command to
+		the device for the specified address. The DPA must be 64-byte
+		aligned and the length of the injected poison is 64-bytes. If
+		successful, the device returns poison when the address is
+		accessed through the CXL.mem bus. Injecting poison adds the
+		address to the device's Poison List and the error source is set
+		to Injected. In addition, the device adds a poison creation
+		event to its internal Informational Event log, updates the
+		Event Status register, and if configured, interrupts the host.
+		It is not an error to inject poison into an address that
+		already has poison present and no error is returned. The
+		inject_poison attribute is only visible for devices supporting
+		the capability.
+
+
+What:		/sys/kernel/debug/memX/clear_poison
+Date:		April, 2023
+KernelVersion:	v6.4
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		(WO) When a Device Physical Address (DPA) is written to this
+		attribute, the memdev driver sends a clear poison command to
+		the device for the specified address. Clearing poison removes
+		the address from the device's Poison List and writes 0 (zero)
+		for 64 bytes starting at address. It is not an error to clear
+		poison from an address that does not have poison set. If the
+		device cannot clear poison from the address, -ENXIO is returned.
+		The clear_poison attribute is only visible for devices
+		supporting the capability.

drivers/cxl/mem.c

@@ -94,6 +94,26 @@ static int devm_cxl_add_endpoint(struct device *host, struct cxl_memdev *cxlmd,
 	return 0;
 }
 
+static int cxl_debugfs_poison_inject(void *data, u64 dpa)
+{
+	struct cxl_memdev *cxlmd = data;
+
+	return cxl_inject_poison(cxlmd, dpa);
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(cxl_poison_inject_fops, NULL,
+			 cxl_debugfs_poison_inject, "%llx\n");
+
+static int cxl_debugfs_poison_clear(void *data, u64 dpa)
+{
+	struct cxl_memdev *cxlmd = data;
+
+	return cxl_clear_poison(cxlmd, dpa);
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(cxl_poison_clear_fops, NULL,
+			 cxl_debugfs_poison_clear, "%llx\n");
+
 static int cxl_mem_probe(struct device *dev)
 {
 	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
@@ -117,6 +137,14 @@ static int cxl_mem_probe(struct device *dev)
 
 	dentry = cxl_debugfs_create_dir(dev_name(dev));
 	debugfs_create_devm_seqfile(dev, "dpamem", dentry, cxl_mem_dpa_show);
+
+	if (test_bit(CXL_POISON_ENABLED_INJECT, cxlds->poison.enabled_cmds))
+		debugfs_create_file("inject_poison", 0200, dentry, cxlmd,
+				    &cxl_poison_inject_fops);
+	if (test_bit(CXL_POISON_ENABLED_CLEAR, cxlds->poison.enabled_cmds))
+		debugfs_create_file("clear_poison", 0200, dentry, cxlmd,
+				    &cxl_poison_clear_fops);
+
 	rc = devm_add_action_or_reset(dev, remove_debugfs, dentry);
 	if (rc)
 		return rc;