Re: [PATCH v29 4/5] sfc: obtain and map cxl range using devm_cxl_probe_mem

[Richard Cheng <icheng@nvidia.com>]

On Mon, Jun 22, 2026 at 01:40:09PM +0800, alejandro.lucero-palau@amd.com wrote:
> From: Alejandro Lucero <alucerop@amd.com>
> 
> Use core API for safely obtain the CXL range linked to an HDM committed
> by the BIOS. Map such a range for being used as the ctpio buffer.
> 
> A potential user space action through sysfs unbinding or core cxl
> modules remove will trigger sfc driver device detachment, with that case
> not racing with this mapping as this is done during driver probe and
> therefore protected with device lock against those user space actions.
> 
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Acked-by: Edward Cree <ecree.xilinx@gmail.com>
> ---
>  drivers/net/ethernet/sfc/efx.c     |  2 ++
>  drivers/net/ethernet/sfc/efx_cxl.c | 23 +++++++++++++++++++++++
>  drivers/net/ethernet/sfc/efx_cxl.h |  3 +++
>  3 files changed, 28 insertions(+)
> 
> diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
> index 61cbb6cfc360..3806cd3dd7f4 100644
> --- a/drivers/net/ethernet/sfc/efx.c
> +++ b/drivers/net/ethernet/sfc/efx.c
> @@ -984,6 +984,7 @@ static void efx_pci_remove(struct pci_dev *pci_dev)
>  	efx_fini_io(efx);
>  
>  	probe_data = container_of(efx, struct efx_probe_data, efx);
> +	efx_cxl_exit(probe_data);
>  
>  	pci_dbg(efx->pci_dev, "shutdown successful\n");
>  
> @@ -1242,6 +1243,7 @@ static int efx_pci_probe(struct pci_dev *pci_dev,
>  	return 0;
>  
>   fail3:
> +	efx_cxl_exit(probe_data);
>  	efx_fini_io(efx);
>   fail2:
>  	efx_fini_struct(efx);
> diff --git a/drivers/net/ethernet/sfc/efx_cxl.c b/drivers/net/ethernet/sfc/efx_cxl.c
> index 18b535b3ea40..3e7c950f83e9 100644
> --- a/drivers/net/ethernet/sfc/efx_cxl.c
> +++ b/drivers/net/ethernet/sfc/efx_cxl.c
> @@ -18,6 +18,7 @@ int efx_cxl_init(struct efx_probe_data *probe_data)
>  {
>  	struct efx_nic *efx = &probe_data->efx;
>  	struct pci_dev *pci_dev = efx->pci_dev;
> +	struct range cxl_pio_range;
>  	struct efx_cxl *cxl;
>  	u16 dvsec;
>  	int rc;
> @@ -73,9 +74,31 @@ int efx_cxl_init(struct efx_probe_data *probe_data)
>  		return -ENODEV;
>  	}
>  
> +	cxl->cxlmd = devm_cxl_probe_mem(&cxl->cxlds, &cxl_pio_range);
> +	if (IS_ERR(cxl->cxlmd)) {
> +		pci_err(pci_dev, "CXL accel memdev creation failed\n");
> +		return PTR_ERR(cxl->cxlmd);
> +	}
> +
> +	cxl->ctpio_cxl = ioremap_wc(cxl_pio_range.start,
> +				    range_len(&cxl_pio_range));

Hi Alejandro,

A small question here,
Is it possible that the FW would commit a region bigger than the range ?
The committed CXL region length is never validated against the PIO window size.
The legacy patch sizes wc_mem_map_size to cover the VI-strided PIO offset, but
here we ioremap whatever the BIOS comitted and assume it's EFX_CTPIO_BUFFER_SIZE.

Maybe adding
"""
if (range_len(&cxl_pio_range) < EFX_CTPIO_BUFFER_SIZE)
    return -EINVAL;
"""
Would be worthy ?

Let me know what you think.

Best regards,
Richard Cheng

> +	if (!cxl->ctpio_cxl) {
> +		pci_err(pci_dev, "CXL ioremap region (%pra) failed\n",
> +			&cxl_pio_range);
> +		return -ENOMEM;
> +	}
> +
>  	probe_data->cxl = cxl;
>  
>  	return 0;
>  }
>  
> +void efx_cxl_exit(struct efx_probe_data *probe_data)
> +{
> +	if (!probe_data->cxl)
> +		return;
> +
> +	iounmap(probe_data->cxl->ctpio_cxl);
> +}
> +
>  MODULE_IMPORT_NS("CXL");
> diff --git a/drivers/net/ethernet/sfc/efx_cxl.h b/drivers/net/ethernet/sfc/efx_cxl.h
> index 04e46278464d..3e2705cb063f 100644
> --- a/drivers/net/ethernet/sfc/efx_cxl.h
> +++ b/drivers/net/ethernet/sfc/efx_cxl.h
> @@ -20,10 +20,13 @@ struct efx_probe_data;
>  struct efx_cxl {
>  	struct cxl_dev_state cxlds;
>  	struct cxl_memdev *cxlmd;
> +	void __iomem *ctpio_cxl;
>  };
>  
>  int efx_cxl_init(struct efx_probe_data *probe_data);
> +void efx_cxl_exit(struct efx_probe_data *probe_data);
>  #else
>  static inline int efx_cxl_init(struct efx_probe_data *probe_data) { return 0; }
> +static inline void efx_cxl_exit(struct efx_probe_data *probe_data) {}
>  #endif
>  #endif
> -- 
> 2.34.1
> 
>