Re: [PATCH 04/20] cxl: Media ready check refactoring

[Dave Jiang]

On 3/11/26 1:34 PM, mhonap@xxxxxxxxxx wrote:
> From: Manish Honap <mhonap@xxxxxxxxxx>
> 
> Before accessing CXL device memory after reset/power-on, the driver
> must ensure media is ready. Not every CXL device implements the CXL
> Memory Device register group (many Type-2 devices do not).
> cxl_await_media_ready() reads cxlds->regs.memdev; calling it
> on a Type-2 without that block can result in kernel panic.

please consider:
Access the memory device registers on a Type-2 device may result in kernel panic.

> 
> This commit refactors the HDM range based check in a new function which
> can be safely used for type-2 and type-3 devices. cxl_await_media_ready
> still uses the same format of checking the HDM range and memory device
> register status.
> 
> Co-developed-by: Zhi Wang <zhiw@xxxxxxxxxx>
> Signed-off-by: Zhi Wang <zhiw@xxxxxxxxxx>
> Signed-off-by: Manish Honap <mhonap@xxxxxxxxxx>

Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>

> ---
>  drivers/cxl/core/pci.c | 35 ++++++++++++++++++++++++++++++-----
>  include/cxl/cxl.h      |  1 +
>  2 files changed, 31 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index 52ed0b4f5e78..2b7e4d73a6dd 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -142,16 +142,24 @@ static int cxl_dvsec_mem_range_active(struct cxl_dev_state *cxlds, int id)
>  	return 0;
>  }
>  
> -/*
> - * Wait up to @media_ready_timeout for the device to report memory
> - * active.
> +/**
> + * cxl_await_range_active - Wait for all HDM DVSEC memory ranges to be active
> + * @cxlds: CXL device state (DVSEC and HDM count must be valid)
> + *
> + * For each HDM decoder range reported in the CXL DVSEC capability, waits for
> + * the range to report MEM INFO VALID (up to 1s per range), then MEM ACTIVE
> + * (up to media_ready_timeout seconds per range, default 60s). Used by
> + * cxl_await_media_ready() and by callers that only need range readiness
> + * without checking the memory device status register.
> + *
> + * Return: 0 if all ranges become valid and active, -ETIMEDOUT if a timeout
> + * occurs, or a negative errno from config read on failure.
>   */
> -int cxl_await_media_ready(struct cxl_dev_state *cxlds)
> +int cxl_await_range_active(struct cxl_dev_state *cxlds)
>  {
>  	struct pci_dev *pdev = to_pci_dev(cxlds->dev);
>  	int d = cxlds->cxl_dvsec;
>  	int rc, i, hdm_count;
> -	u64 md_status;
>  	u16 cap;
>  
>  	rc = pci_read_config_word(pdev,
> @@ -172,6 +180,23 @@ int cxl_await_media_ready(struct cxl_dev_state *cxlds)
>  			return rc;
>  	}
>  
> +	return 0;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_await_range_active, "CXL");
> +
> +/*
> + * Wait up to @media_ready_timeout for the device to report memory
> + * active.
> + */
> +int cxl_await_media_ready(struct cxl_dev_state *cxlds)
> +{
> +	u64 md_status;
> +	int rc;
> +
> +	rc = cxl_await_range_active(cxlds);
> +	if (rc)
> +		return rc;
> +
>  	md_status = readq(cxlds->regs.memdev + CXLMDEV_STATUS_OFFSET);
>  	if (!CXLMDEV_READY(md_status))
>  		return -EIO;
> diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
> index 27c006fa53c3..684603799fb1 100644
> --- a/include/cxl/cxl.h
> +++ b/include/cxl/cxl.h
> @@ -323,5 +323,6 @@ int cxl_find_regblock(struct pci_dev *pdev, enum cxl_regloc_type type,
>  		      struct cxl_register_map *map);
>  void cxl_probe_component_regs(struct device *dev, void __iomem *base,
>  			      struct cxl_component_reg_map *map);
> +int cxl_await_range_active(struct cxl_dev_state *cxlds);
>  
>  #endif /* __CXL_CXL_H__ */