Subject: Re: [PATCH v4 4/6] powerpc/powernv: move core and fadump_release_opalcore under new kobject

From: Greg KH <[email-masked]>
Date: Fri, 6 Dec 2019 13:48:01 +0100

On Fri, Dec 06, 2019 at 05:54:32PM +0530, Sourabh Jain wrote:
> The /sys/firmware/opal/core and /sys/kernel/fadump_release_opalcore sysfs
> files are used to export and release the OPAL memory on PowerNV platform.
> let's organize them into a new kobject under /sys/firmware/opal/mpipl/
> directory.
> 
> A symlink is added to maintain the backward compatibility for
> /sys/firmware/opal/core sysfs file.
> 
> Signed-off-by: Sourabh Jain <[email-masked]>
> ---
>  .../sysfs-kernel-fadump_release_opalcore      |  2 ++
>  .../powerpc/firmware-assisted-dump.rst        | 15 +++++----
>  arch/powerpc/platforms/powernv/opal-core.c    | 31 ++++++++++++++-----
>  3 files changed, 34 insertions(+), 14 deletions(-)
>  rename Documentation/ABI/{testing => removed}/sysfs-kernel-fadump_release_opalcore (82%)
> 
> diff --git a/Documentation/ABI/testing/sysfs-kernel-fadump_release_opalcore b/Documentation/ABI/removed/sysfs-kernel-fadump_release_opalcore
> similarity index 82%
> rename from Documentation/ABI/testing/sysfs-kernel-fadump_release_opalcore
> rename to Documentation/ABI/removed/sysfs-kernel-fadump_release_opalcore
> index 53313c1d4e7a..a8d46cd0f4e6 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-fadump_release_opalcore
> +++ b/Documentation/ABI/removed/sysfs-kernel-fadump_release_opalcore
> @@ -1,3 +1,5 @@
> +This ABI is moved to /sys/firmware/opal/mpipl/release_core.
> +
>  What:		/sys/kernel/fadump_release_opalcore
>  Date:		Sep 2019
>  Contact:	[email-masked]
> diff --git a/Documentation/powerpc/firmware-assisted-dump.rst b/Documentation/powerpc/firmware-assisted-dump.rst
> index 0455a78486d5..345a3405206e 100644
> --- a/Documentation/powerpc/firmware-assisted-dump.rst
> +++ b/Documentation/powerpc/firmware-assisted-dump.rst
> @@ -112,13 +112,13 @@ to ensure that crash data is preserved to process later.
>  
>  -- On OPAL based machines (PowerNV), if the kernel is build with
>     CONFIG_OPAL_CORE=y, OPAL memory at the time of crash is also
> -   exported as /sys/firmware/opal/core file. This procfs file is
> +   exported as /sys/firmware/opal/mpipl/core file. This procfs file is
>     helpful in debugging OPAL crashes with GDB. The kernel memory
>     used for exporting this procfs file can be released by echo'ing
> -   '1' to /sys/kernel/fadump_release_opalcore node.
> +   '1' to /sys/firmware/opal/mpipl/release_core node.
>  
>     e.g.
> -     # echo 1 > /sys/kernel/fadump_release_opalcore
> +     # echo 1 > /sys/firmware/opal/mpipl/release_core
>  
>  Implementation details:
>  -----------------------
> @@ -283,14 +283,17 @@ Here is the list of files under kernel sysfs:
>      enhanced to use this interface to release the memory reserved for
>      dump and continue without 2nd reboot.
>  
> - /sys/kernel/fadump_release_opalcore
> +Note: /sys/kernel/fadump_release_opalcore sysfs has moved to
> +      /sys/firmware/opal/mpipl/release_core
> +
> + /sys/firmware/opal/mpipl/release_core
>  
>      This file is available only on OPAL based machines when FADump is
>      active during capture kernel. This is used to release the memory
> -    used by the kernel to export /sys/firmware/opal/core file. To
> +    used by the kernel to export /sys/firmware/opal/mpipl/core file. To
>      release this memory, echo '1' to it:
>  
> -    echo 1  > /sys/kernel/fadump_release_opalcore
> +    echo 1  > /sys/firmware/opal/mpipl/release_core
>  
>  Here is the list of files under powerpc debugfs:
>  (Assuming debugfs is mounted on /sys/kernel/debug directory.)
> diff --git a/arch/powerpc/platforms/powernv/opal-core.c b/arch/powerpc/platforms/powernv/opal-core.c
> index ed895d82c048..7fcc092d065e 100644
> --- a/arch/powerpc/platforms/powernv/opal-core.c
> +++ b/arch/powerpc/platforms/powernv/opal-core.c
> @@ -589,7 +589,8 @@ static ssize_t fadump_release_opalcore_store(struct kobject *kobj,
>  	return count;
>  }
>  
> -static struct kobj_attribute opalcore_rel_attr = __ATTR(fadump_release_opalcore,
> +struct kobject *mpipl_kobj;
> +static struct kobj_attribute opalcore_rel_attr = __ATTR(release_core,
>  						0200, NULL,
>  						fadump_release_opalcore_store);

__ATTR_WO()?

>  
> @@ -609,7 +610,7 @@ static int __init opalcore_init(void)
>  	 * then capture the dump.
>  	 */
>  	if (!(is_opalcore_usable())) {
> -		pr_err("Failed to export /sys/firmware/opal/core\n");
> +		pr_err("Failed to export /sys/firmware/opal/mpipl/core\n");
>  		opalcore_cleanup();
>  		return rc;
>  	}
> @@ -617,18 +618,32 @@ static int __init opalcore_init(void)
>  	/* Set OPAL core file size */
>  	opal_core_attr.size = oc_conf->opalcore_size;
>  
> +	mpipl_kobj = kobject_create_and_add("mpipl", opal_kobj);
> +	if (!mpipl_kobj) {
> +		pr_err("unable to create mpipl kobject\n");
> +		return -ENOMEM;
> +	}
> +
>  	/* Export OPAL core sysfs file */
> -	rc = sysfs_create_bin_file(opal_kobj, &opal_core_attr);
> +	rc = sysfs_create_bin_file(mpipl_kobj, &opal_core_attr);

Again, create an attribute group and add everything all at once, makes
it much simpler and your error cleanup logic will actually work :)

thanks,

greg k-h