linux-kernel - Re: [PATCH v9 02/19] cxl/mem: Read dynamic capacity configuration from the device

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Message-ID: <681cb309a86e5_2d40892946f@iweiny-mobl.notmuch>
Date: Thu, 8 May 2025 08:35:05 -0500
From: Ira Weiny <ira.weiny@...el.com>
To: Fan Ni <nifan.cxl@...il.com>, Ira Weiny <ira.weiny@...el.com>
CC: Dave Jiang <dave.jiang@...el.com>, Jonathan Cameron
	<Jonathan.Cameron@...wei.com>, Dan Williams <dan.j.williams@...el.com>,
	Davidlohr Bueso <dave@...olabs.net>, Alison Schofield
	<alison.schofield@...el.com>, Vishal Verma <vishal.l.verma@...el.com>,
	<linux-cxl@...r.kernel.org>, <nvdimm@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 02/19] cxl/mem: Read dynamic capacity configuration
 from the device

Fan Ni wrote:
> On Sun, Apr 13, 2025 at 05:52:10PM -0500, Ira Weiny wrote:
> > Devices which optionally support Dynamic Capacity (DC) are configured
> > via mailbox commands.  CXL 3.2 section 9.13.3 requires the host to issue
> > the Get DC Configuration command in order to properly configure DCDs.
> > Without the Get DC Configuration command DCD can't be supported.
> > 
> > Implement the DC mailbox commands as specified in CXL 3.2 section
> > 8.2.10.9.9 (opcodes 48XXh) to read and store the DCD configuration
> > information.  Disable DCD if an invalid configuration is found.
> > 
> > Linux has no support for more than one dynamic capacity partition.  Read
> > and validate all the partitions but configure only the first partition
> > as 'dynamic ram A'.  Additional partitions can be added in the future if
> > such a device ever materializes.  Additionally is it anticipated that no
> > skips will be present from the end of the pmem partition.  Check for an
> > disallow this configuration as well.
> > 
> > Linux has no use for the trailing fields of the Get Dynamic Capacity
> > Configuration Output Payload (Total number of supported extents, number
> > of available extents, total number of supported tags, and number of
> > available tags).  Avoid defining those fields to use the more useful
> > dynamic C array.
> > 
> > Based on an original patch by Navneet Singh.
> > 
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> > 
> > ---
> > Changes:
> > [iweiny: rebase]
> > [iweiny: Update spec references to 3.2]
> > [djbw: Limit to 1 partition]
> > [djbw: Avoid inter-partition skipping]
> > [djbw: s/region/partition/]
> > [djbw: remove cxl_dc_region[partition]_info->name]
> > [iweiny: adjust to lack of dcd_cmds in mds]
> > [iweiny: remove extra 'region' from names]
> > [iweiny: remove unused CXL_DYNAMIC_CAPACITY_SANITIZE_ON_RELEASE_FLAG]
> > ---
> >  drivers/cxl/core/hdm.c  |   2 +
> >  drivers/cxl/core/mbox.c | 179 ++++++++++++++++++++++++++++++++++++++++++++++++
> >  drivers/cxl/cxl.h       |   1 +
> >  drivers/cxl/cxlmem.h    |  54 ++++++++++++++-
> >  drivers/cxl/pci.c       |   3 +
> >  5 files changed, 238 insertions(+), 1 deletion(-)
> ...
> >  /* Set Timestamp CXL 3.0 Spec 8.2.9.4.2 */
> >  struct cxl_mbox_set_timestamp_in {
> >  	__le64 timestamp;
> > @@ -845,9 +871,24 @@ enum {
> >  int cxl_internal_send_cmd(struct cxl_mailbox *cxl_mbox,
> >  			  struct cxl_mbox_cmd *cmd);
> >  int cxl_dev_state_identify(struct cxl_memdev_state *mds);
> > +
> > +struct cxl_mem_dev_info {
> > +	u64 total_bytes;
> > +	u64 volatile_bytes;
> > +	u64 persistent_bytes;
> > +};
> 
> Defined, but never used.

Shoot...  That was from a previous version of work on type2...

Thanks for the catch!
Ira

[snip]