[PATCH v4 6/6] powerpc/fadump: sysfs for fadump memory reservation

[Sourabh Jain]

Add a sys interface to allow querying the memory reserved by FADump for
saving the crash dump.

Also added Documentation/ABI for the new sysfs file.

Signed-off-by: Sourabh Jain <sourabhjain at linux.ibm.com>
---
 Documentation/ABI/testing/sysfs-kernel-fadump    |  7 +++++++
 Documentation/powerpc/firmware-assisted-dump.rst |  5 +++++
 arch/powerpc/kernel/fadump.c                     | 15 +++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-kernel-fadump b/Documentation/ABI/testing/sysfs-kernel-fadump
index 5d988b919e81..8f7a64a81783 100644
--- a/Documentation/ABI/testing/sysfs-kernel-fadump
+++ b/Documentation/ABI/testing/sysfs-kernel-fadump
@@ -31,3 +31,10 @@ Description:	write only
 		the system is booted to capture the vmcore using FADump.
 		It is used to release the memory reserved by FADump to
 		save the crash dump.
+
+What:		/sys/kernel/fadump/mem_reserved
+Date:		Dec 2019
+Contact:	linuxppc-dev at lists.ozlabs.org
+Description:	read only
+		Provide information about the amount of memory reserved by
+		FADump to save the crash dump in bytes.
diff --git a/Documentation/powerpc/firmware-assisted-dump.rst b/Documentation/powerpc/firmware-assisted-dump.rst
index 365c10209ef3..04993eaf3113 100644
--- a/Documentation/powerpc/firmware-assisted-dump.rst
+++ b/Documentation/powerpc/firmware-assisted-dump.rst
@@ -268,6 +268,11 @@ Here is the list of files under kernel sysfs:
     be handled and vmcore will not be captured. This interface can be
     easily integrated with kdump service start/stop.
 
+ /sys/kernel/fadump/mem_reserved
+
+   This is used to display the memory reserved by FADump for saving the
+   crash dump.
+
  /sys/kernel/fadump_release_mem
     This file is available only when FADump is active during
     second kernel. This is used to release the reserved memory
diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index 41a3cda81791..b2af51b7c750 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -1357,6 +1357,13 @@ static ssize_t fadump_enabled_show(struct kobject *kobj,
 	return sprintf(buf, "%d\n", fw_dump.fadump_enabled);
 }
 
+static ssize_t fadump_mem_reserved_show(struct kobject *kobj,
+					struct kobj_attribute *attr,
+					char *buf)
+{
+	return sprintf(buf, "%ld\n", fw_dump.reserve_dump_area_size);
+}
+
 static ssize_t fadump_register_show(struct kobject *kobj,
 					struct kobj_attribute *attr,
 					char *buf)
@@ -1430,6 +1437,10 @@ static struct kobj_attribute enable_attr = __ATTR(enabled,
 static struct kobj_attribute register_attr = __ATTR(registered,
 						0644, fadump_register_show,
 						fadump_register_store);
+static struct kobj_attribute mem_reserved_attr = __ATTR(mem_reserved,
+						0444, fadump_mem_reserved_show,
+						NULL);
+
 
 DEFINE_SHOW_ATTRIBUTE(fadump_region);
 
@@ -1464,6 +1475,10 @@ static void fadump_init_files(void)
 			pr_err("unable to create release_mem sysfs file (%d)\n",
 			       rc);
 	}
+	rc = sysfs_create_file(fadump_kobj, &mem_reserved_attr.attr);
+	if (rc)
+		pr_err("unable to create mem_reserved sysfs file (%d)\n",
+		       rc);
 
 	/* The FADump sysfs are moved from kernel_kobj to fadump_kobj need to
 	 * create symlink at old location to maintain backward compatibility.
-- 
2.17.2