Re: [PATCH v2 10/15] cxl: define a driver interface for DPA allocation

Fan Ni
2024-08-06T17:34:08Z

On Mon, Jul 15, 2024 at 06:28:30PM +0100, alejandro.lucero-palau@amd.com wrote:
> From: Alejandro Lucero <alucerop@amd.com>
>
> Region creation involves finding available DPA (device-physical-address)
> capacity to map into HPA (host-physical-address) space. Given the HPA
> capacity constraint, define an API, cxl_request_dpa(), that has the
> flexibility to map the minimum amount of memory the driver needs to
> operate vs the total possible that can be mapped given HPA availability.
>
> Factor out the core of cxl_dpa_alloc, that does free space scanning,
> into a cxl_dpa_freespace() helper, and use that to balance the capacity
> available to map vs the @min and @max arguments to cxl_request_dpa.
>
> Based on https://lore.kernel.org/linux-cxl/168592149709.1948938.8663425987110396027.stgit@dwillia2-xfh.jf.intel.com/T/#m4271ee49a91615c8af54e3ab20679f8be3099393
>
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> Co-developed-by: Dan Williams <dan.j.williams@intel.com>
> ---
> drivers/cxl/core/core.h | 1 +
> drivers/cxl/core/hdm.c | 153 +++++++++++++++++++++++++----
> drivers/net/ethernet/sfc/efx.c | 2 +
> drivers/net/ethernet/sfc/efx_cxl.c | 18 +++-
> drivers/net/ethernet/sfc/efx_cxl.h | 1 +
> include/linux/cxl_accel_mem.h | 7 ++
> 6 files changed, 161 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
> index 625394486459..a243ff12c0f4 100644
> --- a/drivers/cxl/core/core.h
> +++ b/drivers/cxl/core/core.h
> @@ -76,6 +76,7 @@ int cxl_dpa_set_mode(struct cxl_endpoint_decoder *cxled,
> enum cxl_decoder_mode mode);
> int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size);
> int cxl_dpa_free(struct cxl_endpoint_decoder *cxled);
> +int cxl_dpa_free(struct cxl_endpoint_decoder *cxled);

Function declared twice here.

Fan
> resource_size_t cxl_dpa_size(struct cxl_endpoint_decoder *cxled);
> resource_size_t cxl_dpa_resource_start(struct cxl_endpoint_decoder *cxled);
>
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 4af9225d4b59..3e53ae222d40 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -3,6 +3,7 @@
> #include <linux/seq_file.h>
> #include <linux/device.h>
> #include <linux/delay.h>
> +#include <linux/cxl_accel_mem.h>
>
> #include "cxlmem.h"
> #include "core.h"
> @@ -420,6 +421,7 @@ int cxl_dpa_free(struct cxl_endpoint_decoder *cxled)
> up_write(&cxl_dpa_rwsem);
> return rc;
> }
> +EXPORT_SYMBOL_NS_GPL(cxl_dpa_free, CXL);
>
> int cxl_dpa_set_mode(struct cxl_endpoint_decoder *cxled,
> enum cxl_decoder_mode mode)
> @@ -467,30 +469,17 @@ int cxl_dpa_set_mode(struct cxl_endpoint_decoder *cxled,
> return rc;
> }
>
> -int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size)
> +static resource_size_t cxl_dpa_freespace(struct cxl_endpoint_decoder *cxled,
> + resource_size_t *start_out,
> + resource_size_t *skip_out)
> {
> struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
> resource_size_t free_ram_start, free_pmem_start;
> - struct cxl_port *port = cxled_to_port(cxled);
> struct cxl_dev_state *cxlds = cxlmd->cxlds;
> - struct device *dev = &cxled->cxld.dev;
> resource_size_t start, avail, skip;
> struct resource *p, *last;
> - int rc;
> -
> - down_write(&cxl_dpa_rwsem);
> - if (cxled->cxld.region) {
> - dev_dbg(dev, "decoder attached to %s\n",
> - dev_name(&cxled->cxld.region->dev));
> - rc = -EBUSY;
> - goto out;
> - }
>
> - if (cxled->cxld.flags & CXL_DECODER_F_ENABLE) {
> - dev_dbg(dev, "decoder enabled\n");
> - rc = -EBUSY;
> - goto out;
> - }
> + lockdep_assert_held(&cxl_dpa_rwsem);
>
> for (p = cxlds->ram_res.child, last = NULL; p; p = p->sibling)
> last = p;
> @@ -528,14 +517,45 @@ int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size)
> skip_end = start - 1;
> skip = skip_end - skip_start + 1;
> } else {
> - dev_dbg(dev, "mode not set\n");
> - rc = -EINVAL;
> + avail = 0;
> + }
> +
> + if (!avail)
> + return 0;
> + if (start_out)
> + *start_out = start;
> + if (skip_out)
> + *skip_out = skip;
> + return avail;
> +}
> +
> +int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size)
> +{
> + struct cxl_port *port = cxled_to_port(cxled);
> + struct device *dev = &cxled->cxld.dev;
> + resource_size_t start, avail, skip;
> + int rc;
> +
> + down_write(&cxl_dpa_rwsem);
> + if (cxled->cxld.region) {
> + dev_dbg(dev, "EBUSY, decoder attached to %s\n",
> + dev_name(&cxled->cxld.region->dev));
> + rc = -EBUSY;
> goto out;
> }
>
> + if (cxled->cxld.flags & CXL_DECODER_F_ENABLE) {
> + dev_dbg(dev, "EBUSY, decoder enabled\n");
> + rc = -EBUSY;
> + goto out;
> + }
> +
> + avail = cxl_dpa_freespace(cxled, &start, &skip);
> +
> if (size > avail) {
> dev_dbg(dev, "%pa exceeds available %s capacity: %pa\n", &size,
> - cxl_decoder_mode_name(cxled->mode), &avail);
> + cxled->mode == CXL_DECODER_RAM ? "ram" : "pmem",
> + &avail);
> rc = -ENOSPC;
> goto out;
> }
> @@ -550,6 +570,99 @@ int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size)
> return devm_add_action_or_reset(&port->dev, cxl_dpa_release, cxled);
> }
>
> +static int find_free_decoder(struct device *dev, void *data)
> +{
> + struct cxl_endpoint_decoder *cxled;
> + struct cxl_port *port;
> +
> + if (!is_endpoint_decoder(dev))
> + return 0;
> +
> + cxled = to_cxl_endpoint_decoder(dev);
> + port = cxled_to_port(cxled);
> +
> + if (cxled->cxld.id != port->hdm_end + 1) {
> + return 0;
> + }
> + return 1;
> +}
> +
> +/**
> + * cxl_request_dpa - search and reserve DPA given input constraints
> + * @endpoint: an endpoint port with available decoders
> + * @mode: DPA operation mode (ram vs pmem)
> + * @min: the minimum amount of capacity the call needs
> + * @max: extra capacity to allocate after min is satisfied
> + *
> + * Given that a region needs to allocate from limited HPA capacity it
> + * may be the case that a device has more mappable DPA capacity than
> + * available HPA. So, the expectation is that @min is a driver known
> + * value for how much capacity is needed, and @max is based the limit of
> + * how much HPA space is available for a new region.
> + *
> + * Returns a pinned cxl_decoder with at least @min bytes of capacity
> + * reserved, or an error pointer. The caller is also expected to own the
> + * lifetime of the memdev registration associated with the endpoint to
> + * pin the decoder registered as well.
> + */
> +struct cxl_endpoint_decoder *cxl_request_dpa(struct cxl_port *endpoint,
> + bool is_ram,
> + resource_size_t min,
> + resource_size_t max)
> +{
> + struct cxl_endpoint_decoder *cxled;
> + enum cxl_decoder_mode mode;
> + struct device *cxled_dev;
> + resource_size_t alloc;
> + int rc;
> +
> + if (!IS_ALIGNED(min | max, SZ_256M))
> + return ERR_PTR(-EINVAL);
> +
> + down_read(&cxl_dpa_rwsem);
> +
> + cxled_dev = device_find_child(&endpoint->dev, NULL, find_free_decoder);
> + if (!cxled_dev)
> + cxled = ERR_PTR(-ENXIO);
> + else
> + cxled = to_cxl_endpoint_decoder(cxled_dev);
> +
> + up_read(&cxl_dpa_rwsem);
> +
> + if (IS_ERR(cxled))
> + return cxled;
> +
> + if (is_ram)
> + mode = CXL_DECODER_RAM;
> + else
> + mode = CXL_DECODER_PMEM;
> +
> + rc = cxl_dpa_set_mode(cxled, mode);
> + if (rc)
> + goto err;
> +
> + down_read(&cxl_dpa_rwsem);
> + alloc = cxl_dpa_freespace(cxled, NULL, NULL);
> + up_read(&cxl_dpa_rwsem);
> +
> + if (max)
> + alloc = min(max, alloc);
> + if (alloc < min) {
> + rc = -ENOMEM;
> + goto err;
> + }
> +
> + rc = cxl_dpa_alloc(cxled, alloc);
> + if (rc)
> + goto err;
> +
> + return cxled;
> +err:
> + put_device(cxled_dev);
> + return ERR_PTR(rc);
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_request_dpa, CXL);
> +
> static void cxld_set_interleave(struct cxl_decoder *cxld, u32 *ctrl)
> {
> u16 eig;
> diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
> index cb3f74d30852..9cfe29002d98 100644
> --- a/drivers/net/ethernet/sfc/efx.c
> +++ b/drivers/net/ethernet/sfc/efx.c
> @@ -901,6 +901,8 @@ static void efx_pci_remove(struct pci_dev *pci_dev)
>
> efx_fini_io(efx);
>
> + efx_cxl_exit(efx);
> +
> pci_dbg(efx->pci_dev, "shutdown successful\n");
>
> efx_fini_devlink_and_unlock(efx);
> diff --git a/drivers/net/ethernet/sfc/efx_cxl.c b/drivers/net/ethernet/sfc/efx_cxl.c
> index 6d49571ccff7..b5626d724b52 100644
> --- a/drivers/net/ethernet/sfc/efx_cxl.c
> +++ b/drivers/net/ethernet/sfc/efx_cxl.c
> @@ -84,12 +84,28 @@ void efx_cxl_init(struct efx_nic *efx)
> goto out;
> }
>
> - if (max < EFX_CTPIO_BUFFER_SIZE)
> + if (max < EFX_CTPIO_BUFFER_SIZE) {
> pci_info(pci_dev, "CXL accel not enough free HPA space %llu < %u\n",
> max, EFX_CTPIO_BUFFER_SIZE);
> + goto out;
> + }
> +
> + cxl->cxled = cxl_request_dpa(cxl->endpoint, true, EFX_CTPIO_BUFFER_SIZE,
> + EFX_CTPIO_BUFFER_SIZE);
> + if (IS_ERR(cxl->cxled))
> + pci_info(pci_dev, "CXL accel request DPA failed");
> out:
> cxl_release_endpoint(cxl->cxlmd, cxl->endpoint);
> }
>
> +void efx_cxl_exit(struct efx_nic *efx)
> +{
> + struct efx_cxl *cxl = efx->cxl;
> +
> + if (cxl->cxled)
> + cxl_dpa_free(cxl->cxled);
> +
> + return;
> + }
>
> MODULE_IMPORT_NS(CXL);
> diff --git a/drivers/net/ethernet/sfc/efx_cxl.h b/drivers/net/ethernet/sfc/efx_cxl.h
> index 76c6794c20d8..59d5217a684c 100644
> --- a/drivers/net/ethernet/sfc/efx_cxl.h
> +++ b/drivers/net/ethernet/sfc/efx_cxl.h
> @@ -26,4 +26,5 @@ struct efx_cxl {
> };
>
> void efx_cxl_init(struct efx_nic *efx);
> +void efx_cxl_exit(struct efx_nic *efx);
> #endif
> diff --git a/include/linux/cxl_accel_mem.h b/include/linux/cxl_accel_mem.h
> index f3e77688ffe0..d4ecb5bb4fc8 100644
> --- a/include/linux/cxl_accel_mem.h
> +++ b/include/linux/cxl_accel_mem.h
> @@ -2,6 +2,7 @@
> /* Copyright(c) 2024 Advanced Micro Devices, Inc. */
>
> #include <linux/cdev.h>
> +#include <linux/pci.h>
>
> #ifndef __CXL_ACCEL_MEM_H
> #define __CXL_ACCEL_MEM_H
> @@ -41,4 +42,10 @@ struct cxl_root_decoder *cxl_get_hpa_freespace(struct cxl_port *endpoint,
> int interleave_ways,
> unsigned long flags,
> resource_size_t *max);
> +
> +struct cxl_endpoint_decoder *cxl_request_dpa(struct cxl_port *endpoint,
> + bool is_ram,
> + resource_size_t min,
> + resource_size_t max);
> +int cxl_dpa_free(struct cxl_endpoint_decoder *cxled);
> #endif
> --
> 2.17.1
>