Re: [RFC 02/13] cxl: introduce cxl_get_hdm_info()

Jonathan Cameron
2024-10-17T15:45:03Z

On Fri, 20 Sep 2024 15:34:35 -0700
Zhi Wang <zhiw@nvidia.com> wrote:

> CXL core has the information of what CXL register groups a device has.
> When initializing the device, the CXL core probes the register groups
> and saves the information. The probing sequence is quite complicated.
>
> vfio-cxl requires the HDM register information to emualte the HDM decoder
Hi Zhi,

I know these were a bit rushed out so I'll only comment once.
Give your patch descriptions a spell check (I always forget :)
emulate

> registers.
>
> Introduce cxl_get_hdm_info() for vfio-cxl to leverage the HDM
> register information in the CXL core. Thus, it doesn't need to implement
> its own probing sequence.
>
> Signed-off-by: Zhi Wang <zhiw@nvidia.com>
> ---
> drivers/cxl/core/pci.c | 28 ++++++++++++++++++++++++++++
> drivers/cxl/cxlpci.h | 3 +++
> include/linux/cxl_accel_mem.h | 2 ++
> 3 files changed, 33 insertions(+)
>
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index a663e7566c48..7b6c2b6211b3 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -502,6 +502,34 @@ int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,
> }
> EXPORT_SYMBOL_NS_GPL(cxl_hdm_decode_init, CXL);
>
> +int cxl_get_hdm_info(struct cxl_dev_state *cxlds, u32 *hdm_count,
> + u64 *hdm_reg_offset, u64 *hdm_reg_size)
> +{
> + struct pci_dev *pdev = to_pci_dev(cxlds->dev);
> + int d = cxlds->cxl_dvsec;
> + u16 cap;
> + int rc;
> +
> + if (!cxlds->reg_map.component_map.hdm_decoder.valid) {
> + *hdm_reg_offset = *hdm_reg_size = 0;
Probably want to zero out the hdm_count as well?

> + } else {
> + struct cxl_component_reg_map *map =
> + &cxlds->reg_map.component_map;
> +
> + *hdm_reg_offset = map->hdm_decoder.offset;
> + *hdm_reg_size = map->hdm_decoder.size;
> + }
> +
> + rc = pci_read_config_word(pdev,
> + d + CXL_DVSEC_CAP_OFFSET, &cap);
> + if (rc)
> + return rc;
> +
> + *hdm_count = FIELD_GET(CXL_DVSEC_HDM_COUNT_MASK, cap);
> + return 0;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_get_hdm_info, CXL);