Re: [PATCH v5 3/8] cxl/edac: Add CXL memory device patrol scrub control feature

Alison Schofield
2025-05-20T02:02:30Z

On Thu, May 15, 2025 at 12:59:19PM +0100, shiju.jose@huawei.com wrote:
> From: Shiju Jose <shiju.jose@huawei.com>
>
> CXL spec 3.2 section 8.2.10.9.11.1 describes the device patrol scrub
> control feature. The device patrol scrub proactively locates and makes
> corrections to errors in regular cycle.
>

snip

> +
> +static int cxl_scrub_get_attrbs(struct cxl_patrol_scrub_context *cxl_ps_ctx,
> + u8 *cap, u16 *cycle, u8 *flags, u8 *min_cycle)
> +{
> + struct cxl_mailbox *cxl_mbox;
> + u8 min_scrub_cycle = U8_MAX;
> + struct cxl_memdev *cxlmd;
> + int i, ret;
> +
> + if (cxl_ps_ctx->cxlr) {
> + struct cxl_region *cxlr = cxl_ps_ctx->cxlr;
> + struct cxl_region_params *p = &cxlr->params;

This function and the next, have a big if { } wrapper around
cxlr existence. Can this logic be reversed -

ie, declare cxl_region and cxl_region_params in the header and
then do something like -

if (!cxl_ps_ctx->cxlr) {
cxl_mbox = &cxl_ps_ctx->cxlmd->cxlds->cxl_mbox;
return cxl_mem_scrub_get_attrbs(cxl_mbox, cap, cycle, flags, min_cycle);
}

cxlr = cxl_ps_ctx->cxlr;
p = &cxlr->params;

Then all this code below can shift left.

> +
> + struct rw_semaphore *region_lock __free(rwsem_read_release) =
> + rwsem_read_intr_acquire(&cxl_region_rwsem);
> + if (!region_lock)
> + return -EINTR;
> +
> + for (i = 0; i < p->nr_targets; i++) {
> + struct cxl_endpoint_decoder *cxled = p->targets[i];
> +
> + cxlmd = cxled_to_memdev(cxled);
> + cxl_mbox = &cxlmd->cxlds->cxl_mbox;
> + ret = cxl_mem_scrub_get_attrbs(cxl_mbox, cap, cycle,
> + flags, min_cycle);
> + if (ret)
> + return ret;
> +
> + if (min_cycle)
> + min_scrub_cycle =
> + min(*min_cycle, min_scrub_cycle);
> + }
> +
> + if (min_cycle)
> + *min_cycle = min_scrub_cycle;
> +
> + return 0;
> + }
> + cxl_mbox = &cxl_ps_ctx->cxlmd->cxlds->cxl_mbox;
> +
> + return cxl_mem_scrub_get_attrbs(cxl_mbox, cap, cycle, flags, min_cycle);
> +}
> +
> +static int cxl_scrub_set_attrbs(struct device *dev,
> + struct cxl_patrol_scrub_context *cxl_ps_ctx,
> + u8 cycle, u8 flags)
> +{
> + struct cxl_scrub_wr_attrbs wr_attrbs;
> + struct cxl_mailbox *cxl_mbox;
> + struct cxl_memdev *cxlmd;
> + int ret, i;
> +
> + wr_attrbs.scrub_cycle_hours = cycle;
> + wr_attrbs.scrub_flags = flags;
> +
> + if (cxl_ps_ctx->cxlr) {
> + struct cxl_region *cxlr = cxl_ps_ctx->cxlr;
> + struct cxl_region_params *p = &cxlr->params;

Similar to above function, but more work in the !cxlr case. Maybe a goto.

> +
> + struct rw_semaphore *region_lock __free(rwsem_read_release) =
> + rwsem_read_intr_acquire(&cxl_region_rwsem);
> + if (!region_lock)
> + return -EINTR;
> +
> + for (i = 0; i < p->nr_targets; i++) {
> + struct cxl_endpoint_decoder *cxled = p->targets[i];
> +
> + cxlmd = cxled_to_memdev(cxled);
> + cxl_mbox = &cxlmd->cxlds->cxl_mbox;
> + ret = cxl_set_feature(cxl_mbox, &CXL_FEAT_PATROL_SCRUB_UUID,
> + cxl_ps_ctx->set_version, &wr_attrbs,
> + sizeof(wr_attrbs),
> + CXL_SET_FEAT_FLAG_DATA_SAVED_ACROSS_RESET,
> + 0, NULL);
> + if (ret)
> + return ret;
> +
> + if (cycle != cxlmd->cur_scrub_cycle) {
> + if (cxlmd->cur_region_id != -1)
> + dev_info(dev,
> + "Device scrub rate(%d hours) set by region%d rate overwritten by region%d scrub rate(%d hours)\n",
> + cxlmd->cur_scrub_cycle,
> + cxlmd->cur_region_id, cxlr->id,
> + cycle);
> +
> + cxlmd->cur_scrub_cycle = cycle;
> + cxlmd->cur_region_id = cxlr->id;
> + }
> + }
> +
> + return 0;
> + }
> +
> + cxlmd = cxl_ps_ctx->cxlmd;
> + cxl_mbox = &cxlmd->cxlds->cxl_mbox;
> + ret = cxl_set_feature(cxl_mbox, &CXL_FEAT_PATROL_SCRUB_UUID,
> + cxl_ps_ctx->set_version, &wr_attrbs,
> + sizeof(wr_attrbs),
> + CXL_SET_FEAT_FLAG_DATA_SAVED_ACROSS_RESET, 0,
> + NULL);
> + if (ret)
> + return ret;
> +
> + if (cycle != cxlmd->cur_scrub_cycle) {
> + if (cxlmd->cur_region_id != -1)
> + dev_info(dev,
> + "Device scrub rate(%d hours) set by region%d rate overwritten with device local scrub rate(%d hours)\n",
> + cxlmd->cur_scrub_cycle, cxlmd->cur_region_id,
> + cycle);
> +
> + cxlmd->cur_scrub_cycle = cycle;
> + cxlmd->cur_region_id = -1;
> + }
> +
> + return 0;
> +}
> +

skip

> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> index 3ec6b906371b..685957b312ea 100644
> --- a/drivers/cxl/cxlmem.h
> +++ b/drivers/cxl/cxlmem.h
> @@ -45,6 +45,8 @@
> * @endpoint: connection to the CXL port topology for this memory device
> * @id: id number of this memdev instance.
> * @depth: endpoint port depth
> + * @cur_scrub_cycle: current scrub cycle set for this device
> + * @cur_region_id: id number of a backed region (if any) for which current scrub cycle set
> */
> struct cxl_memdev {
> struct device dev;
> @@ -56,6 +58,10 @@ struct cxl_memdev {
> struct cxl_port *endpoint;
> int id;
> int depth;
> +#ifdef CONFIG_CXL_EDAC_SCRUB
> + u8 cur_scrub_cycle;
> + int cur_region_id;
> +#endif
> };

Why the cur_ prefix? Seems like it's just 'the' scrub cycle.

How about:

s/cur_scrub_cycle/scrub_cycle
s/cur_region_id/scrub_region_id

That also makes it clear that the region_id is related to the scrub.

Somewhere later cur_region_id gets compared to -1 a few times.
Perhaps add a define for that like #define CXL_SCRUB_NO_REGION -1

>
> static inline struct cxl_memdev *to_cxl_memdev(struct device *dev)
> @@ -853,6 +859,16 @@ int cxl_trigger_poison_list(struct cxl_memdev *cxlmd);
> int cxl_inject_poison(struct cxl_memdev *cxlmd, u64 dpa);
> int cxl_clear_poison(struct cxl_memdev *cxlmd, u64 dpa);
>
> +#if IS_ENABLED(CONFIG_CXL_EDAC_MEM_FEATURES)

that's the one I mentioned in cover letter that can be #ifdef

> +int devm_cxl_memdev_edac_register(struct cxl_memdev *cxlmd);
> +int devm_cxl_region_edac_register(struct cxl_region *cxlr);
> +#else
> +static inline int devm_cxl_memdev_edac_register(struct cxl_memdev *cxlmd)
> +{ return 0; }
> +static inline int devm_cxl_region_edac_register(struct cxl_region *cxlr)
> +{ return 0; }
> +#endif
> +
> #ifdef CONFIG_CXL_SUSPEND
> void cxl_mem_active_inc(void);
> void cxl_mem_active_dec(void);
> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> index 9675243bd05b..6e6777b7bafb 100644
> --- a/drivers/cxl/mem.c
> +++ b/drivers/cxl/mem.c
> @@ -180,6 +180,10 @@ static int cxl_mem_probe(struct device *dev)
> return rc;
> }
>
> + rc = devm_cxl_memdev_edac_register(cxlmd);
> + if (rc)
> + dev_dbg(dev, "CXL memdev EDAC registration failed rc=%d\n", rc);
> +
> /*
> * The kernel may be operating out of CXL memory on this device,
> * there is no spec defined way to determine whether this device
> --
> 2.43.0
>
>