Re: [PATCH v20 18/22] cxl: Allow region creation by type2 drivers

Alejandro Lucero Palau
2025-11-19T18:31:26Z

On 11/12/25 16:19, Jonathan Cameron wrote:
> On Mon, 10 Nov 2025 15:36:53 +0000
> alejandro.lucero-palau@amd.com wrote:
>
>> From: Alejandro Lucero <alucerop@amd.com>
>>
>> Creating a CXL region requires userspace intervention through the cxl
>> sysfs files. Type2 support should allow accelerator drivers to create
>> such cxl region from kernel code.
>>
>> Adding that functionality and integrating it with current support for
>> memory expanders. Only support uncommitted CXL_DECODER_DEVMEM decoders.
>>
>> Based on https://lore.kernel.org/linux-cxl/168592159835.1948938.1647215579839222774.stgit@dwillia2-xfh.jf.intel.com/
>>
>> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> One minor suggestion that I made very late in v19 thread.
> Either way:
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
>
>> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
>> index 2424d1b35cee..63c9c5f92252 100644
>> --- a/drivers/cxl/core/region.c
>> +++ b/drivers/cxl/core/region.c
> ...
>
>> +static struct cxl_region *
>> +__construct_new_region(struct cxl_root_decoder *cxlrd,
>> + struct cxl_endpoint_decoder **cxled, int ways)
>> +{
>> + struct cxl_memdev *cxlmd = cxled_to_memdev(cxled[0]);
>> + struct cxl_decoder *cxld = &cxlrd->cxlsd.cxld;
>> + struct cxl_region_params *p;
>> + resource_size_t size = 0;
>> + int rc, i;
>> +
>> + struct cxl_region *cxlr __free(cxl_region_drop) =
>> + construct_region_begin(cxlrd, cxled[0]);
>> + if (IS_ERR(cxlr))
>> + return cxlr;
>> +
>> + guard(rwsem_write)(&cxl_rwsem.region);
>> +
>> + /*
>> + * Sanity check. This should not happen with an accel driver handling
>> + * the region creation.
>> + */
>> + p = &cxlr->params;
>> + if (p->state >= CXL_CONFIG_INTERLEAVE_ACTIVE) {
>> + dev_err(cxlmd->dev.parent,
>> + "%s:%s: %s unexpected region state\n",
>> + dev_name(&cxlmd->dev), dev_name(&cxled[0]->cxld.dev),
>> + __func__);
>> + return ERR_PTR(-EBUSY);
>> + }
>> +
>> + rc = set_interleave_ways(cxlr, ways);
>> + if (rc)
>> + return ERR_PTR(rc);
>> +
>> + rc = set_interleave_granularity(cxlr, cxld->interleave_granularity);
>> + if (rc)
>> + return ERR_PTR(rc);
>> +
>> + scoped_guard(rwsem_read, &cxl_rwsem.dpa) {
>> + for (i = 0; i < ways; i++) {
>> + if (!cxled[i]->dpa_res)
>> + break;
>> + size += resource_size(cxled[i]->dpa_res);
>> + }
>> + if (i < ways)
>> + return ERR_PTR(-EINVAL);
> I came in late on v19 thread with a comment on this.
>
>
> for (i = 0; i < ways; i++) {
> if (!cxled[i]->dpa_res)
> return ERR_PTR(-EINVAL);
> size += resource_size(cxled[i]->dpa_res);
> }
> Is the same but simpler.

I agree. I'll use it.

Thanks!

>
>> +
>> + rc = alloc_hpa(cxlr, size);
>> + if (rc)
>> + return ERR_PTR(rc);
>> +
>> + for (i = 0; i < ways; i++) {
>> + rc = cxl_region_attach(cxlr, cxled[i], 0);
>> + if (rc)
>> + return ERR_PTR(rc);
>> + }
>> + }
>> +
>> + rc = cxl_region_decode_commit(cxlr);
>> + if (rc)
>> + return ERR_PTR(rc);
>> +
>> + p->state = CXL_CONFIG_COMMIT;
>> +
>> + return no_free_ptr(cxlr);
>> +}