Re: [PATCH 2/3] cxl/mem: Support sanitation commands

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Mon, 19 Dec 2022 12:47:44 -0800
Davidlohr Bueso <dave@stgolabs.net> wrote:

> On Mon, 19 Dec 2022, Jonathan Cameron wrote:
> 
> >On Mon,  5 Dec 2022 17:15:00 -0800
> >Davidlohr Bueso <dave@stgolabs.net> wrote:
> >  
> >> Implement support for the non-pmem exclusive sanitize (aka overwrite)
> >> and secure erase commands, per CXL specs.
> >>
> >> To properly support this feature, create a 'security' sysfs file that
> >> when read will list the current pmem security state or overwrite, and
> >> when written to, perform the requested operation.
> >>
> >> As with ndctl-speak, the use cases here would be:
> >>  
> >> $> cxl sanitize --erase memX
> >> $> cxl sanitize --overwrite memX
> >> $> cxl sanitize --wait-overwrite memX  
> >>
> >> Where userspace can implement entirely the wait/query mechanism for
> >> waiting for the sanitize to complete (albeit no poll support for
> >> the security sysfs file).
> >>
> >> Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>  
> >
> >Hi Davidlohr,
> >
> >Given I'm late to the game and there has been lots of discussion I'll
> >focus on just the ABI.
> >  
> >> +What:		/sys/bus/cxl/devices/memX/security
> >> +Date:		December, 2022
> >> +KernelVersion:	v6.2
> >> +Contact:	linux-cxl@vger.kernel.org
> >> +Description:
> >> +		Reading this file will display the security state for that
> >> +		device. The following states are available: disabled, frozen,
> >> +		locked, unlocked and overwrite. When writing to the file, the
> >> +		following commands are supported:
> >> +		* overwrite - Sanitize the device to securely re-purpose or
> >> +		  decommission it. This is done by ensuring that all user data
> >> +		  and meta-data, whether it resides in persistent capacity,
> >> +		  volatile capacity, or the label storage area, is made
> >> +		  permanently unavailable by whatever means is appropriate for
> >> +		  the media type. This causes all CPU caches to be flushed.
> >> +		* erase - Secure Erase user data by changing the media encryption
> >> +		  keys for all user data areas of the device. This causes all
> >> +		  CPU caches to be flushed.  
> >
> >General rule of sysfs is one file, one thing.  I think this interface needs splitting.
> >RO attribute security_state
> >WO attribute security_overwrite (or maybe security_sanitize as overwriting is an
> >  implementation choice?)
> >WO attribute security_erase  
> 
> Fine by me. How about instead: security/{state, sanitize, erase}?

Sounds good.

Jonathan