Re: [PATCH 09/26] cxl/region: Add Dynamic Capacity CXL region support

Ira Weiny
2024-04-10T04:35:47Z

Dave Jiang wrote:
>
>
> On 3/24/24 4:18 PM, ira.weiny@intel.com wrote:
> > From: Navneet Singh <navneet.singh@intel.com>
> >

[snip]

> >
> > -What: /sys/bus/cxl/devices/decoderX.Y/create_{pmem,ram}_region
> > -Date: May, 2022, January, 2023
> > -KernelVersion: v6.0 (pmem), v6.3 (ram)
> > +What: /sys/bus/cxl/devices/decoderX.Y/create_{pmem,ram,dc}_region
> > +Date: May, 2022, January, 2023, June 2024
> > +KernelVersion: v6.0 (pmem), v6.3 (ram), v6.10 (dc)
> > Contact: linux-cxl@vger.kernel.org
> > Description:
> > (RW) Write a string in the form 'regionZ' to start the process
> > - of defining a new persistent, or volatile memory region
> > - (interleave-set) within the decode range bounded by root decoder
> > - 'decoderX.Y'. The value written must match the current value
> > - returned from reading this attribute. An atomic compare exchange
> > - operation is done on write to assign the requested id to a
> > - region and allocate the region-id for the next creation attempt.
> > - EBUSY is returned if the region name written does not match the
> > - current cached value.
> > + of defining a new persistent, volatile, or Dynamic Capacity
> > + (DC) memory region (interleave-set) within the decode range
> > + bounded by root decoder 'decoderX.Y'. The value written must
> > + match the current value returned from reading this attribute.
> > + An atomic compare exchange operation is done on write to assign
> > + the requested id to a region and allocate the region-id for the
> > + next creation attempt. EBUSY is returned if the region name
>
> -EBUSY?
>

To match the other documentation I would say no. The other docs show
ENXIO/EBUSY/EINVAL without the negative indicator.

[snip]

> > diff --git a/drivers/dax/cxl.c b/drivers/dax/cxl.c
> > index c696837ab23c..415d03fbf9b6 100644
> > --- a/drivers/dax/cxl.c
> > +++ b/drivers/dax/cxl.c
> > @@ -13,19 +13,30 @@ static int cxl_dax_region_probe(struct device *dev)
> > struct cxl_region *cxlr = cxlr_dax->cxlr;
> > struct dax_region *dax_region;
> > struct dev_dax_data data;
> > + resource_size_t dev_size;
> > + unsigned long flags;
> >
> > if (nid == NUMA_NO_NODE)
> > nid = memory_add_physaddr_to_nid(cxlr_dax->hpa_range.start);
> >
> > + flags = IORESOURCE_DAX_KMEM;
> > + if (cxlr->mode == CXL_REGION_DC)
> > + flags |= IORESOURCE_DAX_SPARSE_CAP;
> > +
> > dax_region = alloc_dax_region(dev, cxlr->id, &cxlr_dax->hpa_range, nid,
> > - PMD_SIZE, IORESOURCE_DAX_KMEM);
> > + PMD_SIZE, flags);
> > if (!dax_region)
> > return -ENOMEM;
> >
> > + dev_size = range_len(&cxlr_dax->hpa_range);
> > + /* Add empty seed dax device */
> > + if (cxlr->mode == CXL_REGION_DC)
> > + dev_size = 0;
>
> Nit. Just do if/else so dev_size isn't set twice if mode is DC.

Ok yea.

Ira