On Fri, Jul 31, 2026 at 01:48:06AM -0700, Anisa Su wrote:
> From: Ira Weiny <[email protected]>
>
> Per the CXL 4.0 specification software must check the Command Effects
> Log (CEL) for dynamic capacity command support.
>
> Detect support for the DCD commands while reading the CEL, including:
>
> Get DC Config
> Get DC Extent List
> Add DC Response
> Release DC
>
> Based on an original patch by Navneet Singh.
>
> Signed-off-by: Ira Weiny <[email protected]>
> Signed-off-by: Anisa Su <[email protected]>
> Tested-by: Wonjae Lee <[email protected]>
> Tested-by: Junhee Park <[email protected]>
> Tested-by: Heesoo Kim <[email protected]>
>
> ---
> Changes:
> 1. mbox.c: leave mds->dcd_supported false so the hardware enablement
> patches can be upstreamed ahead of the extent and DAX work; the
> event handling patch re-enables it.
> ---
> drivers/cxl/core/mbox.c | 44 +++++++++++++++++++++++++++++++++++++++++
> drivers/cxl/cxlmem.h | 20 +++++++++++++++++++
> 2 files changed, 64 insertions(+)
>
> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> index 7c6c5b7450a5..4790524c32a7 100644
> --- a/drivers/cxl/core/mbox.c
> +++ b/drivers/cxl/core/mbox.c
> @@ -165,6 +165,38 @@ static void cxl_set_security_cmd_enabled(struct
> cxl_security_state *security,
> }
> }
>
> +static bool cxl_is_dcd_command(u16 opcode)
> +{
> +#define CXL_MBOX_OP_DCD_CMDS 0x48
> +
> + return (opcode >> 8) == CXL_MBOX_OP_DCD_CMDS;
> +}
> +
> +static void cxl_set_dcd_cmd_enabled(u16 opcode, unsigned long *cmd_mask)
> +{
> + switch (opcode) {
> + case CXL_MBOX_OP_GET_DC_CONFIG:
> + set_bit(CXL_DCD_ENABLED_GET_CONFIG, cmd_mask);
> + break;
> + case CXL_MBOX_OP_GET_DC_EXTENT_LIST:
> + set_bit(CXL_DCD_ENABLED_GET_EXTENT_LIST, cmd_mask);
> + break;
> + case CXL_MBOX_OP_ADD_DC_RESPONSE:
> + set_bit(CXL_DCD_ENABLED_ADD_RESPONSE, cmd_mask);
> + break;
> + case CXL_MBOX_OP_RELEASE_DC:
> + set_bit(CXL_DCD_ENABLED_RELEASE, cmd_mask);
> + break;
> + default:
> + break;
> + }
> +}
> +
> +static bool cxl_verify_dcd_cmds(unsigned long *cmds_seen)
> +{
> + return bitmap_full(cmds_seen, CXL_DCD_ENABLED_MAX);
> +}
> +
> static bool cxl_is_poison_command(u16 opcode)
> {
> #define CXL_MBOX_OP_POISON_CMDS 0x43
> @@ -757,6 +789,7 @@ static void cxl_walk_cel(struct cxl_memdev_state *mds,
> size_t size, u8 *cel)
> struct cxl_mailbox *cxl_mbox = &mds->cxlds.cxl_mbox;
> struct cxl_cel_entry *cel_entry;
> const int cel_entries = size / sizeof(*cel_entry);
> + DECLARE_BITMAP(dcd_cmds, CXL_DCD_ENABLED_MAX) = {};
> struct device *dev = mds->cxlds.dev;
> int i, ro_cmds = 0, wr_cmds = 0;
>
> @@ -785,11 +818,22 @@ static void cxl_walk_cel(struct cxl_memdev_state *mds,
> size_t size, u8 *cel)
> enabled++;
> }
>
> + if (cxl_is_dcd_command(opcode)) {
> + cxl_set_dcd_cmd_enabled(opcode, dcd_cmds);
> + enabled++;
> + }
> +
> dev_dbg(dev, "Opcode 0x%04x %s\n", opcode,
> enabled ? "enabled" : "unsupported by driver");
> }
>
> set_features_cap(cxl_mbox, ro_cmds, wr_cmds);
> + /*
> + * Disabled until event handling implemented.
> + */
> + if (cxl_verify_dcd_cmds(dcd_cmds))
> + dev_dbg(dev, "Device supports DCD; capability disabled\n");
> + mds->dcd_supported = false;
> }
Hi Anisa,
I read and agree with the other reviewers that this does not need to
mirror the poison and security command handling.
The one-use cxl_verify_dcd_cmds() helper still seems excessive. The
bitmap can be checked directly here:
if (bitmap_full(dcd_cmds, CXL_DCD_ENABLED_MAX))
dev_dbg(dev, "Device supports DCD; capability disabled\n");
And then once DCD is ready to be enabled, the assignment can become:
mds->dcd_supported =
bitmap_full(dcd_cmds, CXL_DCD_ENABLED_MAX);
-- Alison
