On Sun, Apr 13, 2025 at 05:52:15PM -0500, Ira Weiny wrote:
> Dynamic Capacity CXL regions must allow memory to be added or removed
> dynamically. In addition to the quantity of memory available the
> location of the memory within a DC partition is dynamic based on the
> extents offered by a device. CXL DAX regions must accommodate the
> sparseness of this memory in the management of DAX regions and devices.
>
> Introduce the concept of a sparse DAX region. Introduce
> create_dynamic_ram_a_region() sysfs entry to create such regions.
> Special case dynamic capable regions to create a 0 sized seed DAX device
> to maintain compatibility which requires a default DAX device to hold a
> region reference.
>
> Indicate 0 byte available capacity until such time that capacity is
> added.
>
> Sparse regions complicate the range mapping of dax devices. There is no
> known use case for range mapping on sparse regions. Avoid the
> complication by preventing range mapping of dax devices on sparse
> regions.
>
> Interleaving is deferred for now. Add checks.
>
> Based on an original patch by Navneet Singh.
>
> Signed-off-by: Ira Weiny <ira.we...@intel.com>
LGTM, although I am not very familiar with dax.
Reviewed-by: Fan Ni <fan...@samsung.com>
>
> ---
> Changes:
> [iweiny: adjust to new partition mode and new singular dynamic ram
> partition]
> ---
> Documentation/ABI/testing/sysfs-bus-cxl | 22 +++++++++----------
> drivers/cxl/core/core.h | 11 ++++++++++
> drivers/cxl/core/port.c | 1 +
> drivers/cxl/core/region.c | 38
> +++++++++++++++++++++++++++++++--
> drivers/dax/bus.c | 10 +++++++++
> drivers/dax/bus.h | 1 +
> drivers/dax/cxl.c | 16 ++++++++++++--
> 7 files changed, 84 insertions(+), 15 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-cxl
> b/Documentation/ABI/testing/sysfs-bus-cxl
> index b2754e6047ca..2e26d95ac66f 100644
> --- a/Documentation/ABI/testing/sysfs-bus-cxl
> +++ b/Documentation/ABI/testing/sysfs-bus-cxl
> @@ -434,20 +434,20 @@ Description:
> interleave_granularity).
>
>
> -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,dynamic_ram_a}_region
> +Date: May, 2022, January, 2023, May 2025
> +KernelVersion: v6.0 (pmem), v6.3 (ram), v6.16 (dynamic_ram_a)
> Contact: linux-...@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 RAM 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.
>
>
> What: /sys/bus/cxl/devices/decoderX.Y/delete_region
> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
> index 15699299dc11..08facbc2d270 100644
> --- a/drivers/cxl/core/core.h
> +++ b/drivers/cxl/core/core.h
> @@ -5,6 +5,7 @@
> #define __CXL_CORE_H__
>
> #include <cxl/mailbox.h>
> +#include <cxlmem.h>
>
> extern const struct device_type cxl_nvdimm_bridge_type;
> extern const struct device_type cxl_nvdimm_type;
> @@ -12,9 +13,19 @@ extern const struct device_type cxl_pmu_type;
>
> extern struct attribute_group cxl_base_attribute_group;
>
> +static inline struct cxl_memdev_state *
> +cxled_to_mds(struct cxl_endpoint_decoder *cxled)
> +{
> + struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> + struct cxl_dev_state *cxlds = cxlmd->cxlds;
> +
> + return container_of(cxlds, struct cxl_memdev_state, cxlds);
> +}
> +
> #ifdef CONFIG_CXL_REGION
> extern struct device_attribute dev_attr_create_pmem_region;
> extern struct device_attribute dev_attr_create_ram_region;
> +extern struct device_attribute dev_attr_create_dynamic_ram_a_region;
> extern struct device_attribute dev_attr_delete_region;
> extern struct device_attribute dev_attr_region;
> extern const struct device_type cxl_pmem_region_type;
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index e98605bd39b4..b2bd24437484 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -334,6 +334,7 @@ static struct attribute *cxl_decoder_root_attrs[] = {
> &dev_attr_qos_class.attr,
> SET_CXL_REGION_ATTR(create_pmem_region)
> SET_CXL_REGION_ATTR(create_ram_region)
> + SET_CXL_REGION_ATTR(create_dynamic_ram_a_region)
> SET_CXL_REGION_ATTR(delete_region)
> NULL,
> };
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index c3f4dc244df7..716d33140ee8 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -480,6 +480,11 @@ static ssize_t interleave_ways_store(struct device *dev,
> if (rc)
> return rc;
>
> + if (cxlr->mode == CXL_PARTMODE_DYNAMIC_RAM_A && val != 1) {
> + dev_err(dev, "Interleaving and DCD not supported\n");
> + return -EINVAL;
> + }
> +
> rc = ways_to_eiw(val, &iw);
> if (rc)
> return rc;
> @@ -2198,6 +2203,7 @@ static size_t store_targetN(struct cxl_region *cxlr,
> const char *buf, int pos,
> if (sysfs_streq(buf, "\n"))
> rc = detach_target(cxlr, pos);
> else {
> + struct cxl_endpoint_decoder *cxled;
> struct device *dev;
>
> dev = bus_find_device_by_name(&cxl_bus_type, NULL, buf);
> @@ -2209,8 +2215,13 @@ static size_t store_targetN(struct cxl_region *cxlr,
> const char *buf, int pos,
> goto out;
> }
>
> - rc = attach_target(cxlr, to_cxl_endpoint_decoder(dev), pos,
> - TASK_INTERRUPTIBLE);
> + cxled = to_cxl_endpoint_decoder(dev);
> + if (cxlr->mode == CXL_PARTMODE_DYNAMIC_RAM_A &&
> + !cxl_dcd_supported(cxled_to_mds(cxled))) {
> + dev_dbg(dev, "DCD unsupported\n");
> + return -EINVAL;
> + }
> + rc = attach_target(cxlr, cxled, pos, TASK_INTERRUPTIBLE);
> out:
> put_device(dev);
> }
> @@ -2555,6 +2566,7 @@ static struct cxl_region *__create_region(struct
> cxl_root_decoder *cxlrd,
> switch (mode) {
> case CXL_PARTMODE_RAM:
> case CXL_PARTMODE_PMEM:
> + case CXL_PARTMODE_DYNAMIC_RAM_A:
> break;
> default:
> dev_err(&cxlrd->cxlsd.cxld.dev, "unsupported mode %d\n", mode);
> @@ -2607,6 +2619,21 @@ static ssize_t create_ram_region_store(struct device
> *dev,
> }
> DEVICE_ATTR_RW(create_ram_region);
>
> +static ssize_t create_dynamic_ram_a_region_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + return __create_region_show(to_cxl_root_decoder(dev), buf);
> +}
> +
> +static ssize_t create_dynamic_ram_a_region_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t len)
> +{
> + return create_region_store(dev, buf, len, CXL_PARTMODE_DYNAMIC_RAM_A);
> +}
> +DEVICE_ATTR_RW(create_dynamic_ram_a_region);
> +
> static ssize_t region_show(struct device *dev, struct device_attribute *attr,
> char *buf)
> {
> @@ -3173,6 +3200,12 @@ static int devm_cxl_add_dax_region(struct cxl_region
> *cxlr)
> struct device *dev;
> int rc;
>
> + if (cxlr->mode == CXL_PARTMODE_DYNAMIC_RAM_A &&
> + cxlr->params.interleave_ways != 1) {
> + dev_err(&cxlr->dev, "Interleaving DC not supported\n");
> + return -EINVAL;
> + }
> +
> cxlr_dax = cxl_dax_region_alloc(cxlr);
> if (IS_ERR(cxlr_dax))
> return PTR_ERR(cxlr_dax);
> @@ -3539,6 +3572,7 @@ static int cxl_region_probe(struct device *dev)
> case CXL_PARTMODE_PMEM:
> return devm_cxl_add_pmem_region(cxlr);
> case CXL_PARTMODE_RAM:
> + case CXL_PARTMODE_DYNAMIC_RAM_A:
> /*
> * The region can not be manged by CXL if any portion of
> * it is already online as 'System RAM'
> diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> index fde29e0ad68b..d8cb5195a227 100644
> --- a/drivers/dax/bus.c
> +++ b/drivers/dax/bus.c
> @@ -178,6 +178,11 @@ static bool is_static(struct dax_region *dax_region)
> return (dax_region->res.flags & IORESOURCE_DAX_STATIC) != 0;
> }
>
> +static bool is_sparse(struct dax_region *dax_region)
> +{
> + return (dax_region->res.flags & IORESOURCE_DAX_SPARSE_CAP) != 0;
> +}
> +
> bool static_dev_dax(struct dev_dax *dev_dax)
> {
> return is_static(dev_dax->region);
> @@ -301,6 +306,9 @@ static unsigned long long dax_region_avail_size(struct
> dax_region *dax_region)
>
> lockdep_assert_held(&dax_region_rwsem);
>
> + if (is_sparse(dax_region))
> + return 0;
> +
> for_each_dax_region_resource(dax_region, res)
> size -= resource_size(res);
> return size;
> @@ -1373,6 +1381,8 @@ static umode_t dev_dax_visible(struct kobject *kobj,
> struct attribute *a, int n)
> return 0;
> if (a == &dev_attr_mapping.attr && is_static(dax_region))
> return 0;
> + if (a == &dev_attr_mapping.attr && is_sparse(dax_region))
> + return 0;
> if ((a == &dev_attr_align.attr ||
> a == &dev_attr_size.attr) && is_static(dax_region))
> return 0444;
> diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h
> index cbbf64443098..783bfeef42cc 100644
> --- a/drivers/dax/bus.h
> +++ b/drivers/dax/bus.h
> @@ -13,6 +13,7 @@ struct dax_region;
> /* dax bus specific ioresource flags */
> #define IORESOURCE_DAX_STATIC BIT(0)
> #define IORESOURCE_DAX_KMEM BIT(1)
> +#define IORESOURCE_DAX_SPARSE_CAP BIT(2)
>
> struct dax_region *alloc_dax_region(struct device *parent, int region_id,
> struct range *range, int target_node, unsigned int align,
> diff --git a/drivers/dax/cxl.c b/drivers/dax/cxl.c
> index 13cd94d32ff7..88b051cea755 100644
> --- a/drivers/dax/cxl.c
> +++ b/drivers/dax/cxl.c
> @@ -13,19 +13,31 @@ 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_PARTMODE_DYNAMIC_RAM_A)
> + 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;
>
> + if (cxlr->mode == CXL_PARTMODE_DYNAMIC_RAM_A)
> + /* Add empty seed dax device */
> + dev_size = 0;
> + else
> + dev_size = range_len(&cxlr_dax->hpa_range);
> +
> data = (struct dev_dax_data) {
> .dax_region = dax_region,
> .id = -1,
> - .size = range_len(&cxlr_dax->hpa_range),
> + .size = dev_size,
> .memmap_on_memory = true,
> };
>
>
> --
> 2.49.0
>
--
Fan Ni (From gmail)
