netdev - Re: [PATCH v16 02/22] sfc: add cxl support

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Message-ID: <682c3129d6a47_2b1610070@dwillia2-mobl4.notmuch>
Date: Tue, 20 May 2025 00:37:13 -0700
From: <dan.j.williams@...el.com>
To: <alejandro.lucero-palau@....com>, <linux-cxl@...r.kernel.org>,
	<netdev@...r.kernel.org>, <dan.j.williams@...el.com>, <edward.cree@....com>,
	<davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<edumazet@...gle.com>, <dave.jiang@...el.com>
CC: Alejandro Lucero <alucerop@....com>, Jonathan Cameron
	<Jonathan.Cameron@...wei.com>, Edward Cree <ecree.xilinx@...il.com>
Subject: Re: [PATCH v16 02/22] sfc: add cxl support

alejandro.lucero-palau@ wrote:
> From: Alejandro Lucero <alucerop@....com>
> 
> Add CXL initialization based on new CXL API for accel drivers and make
> it dependent on kernel CXL configuration.
> 
> Signed-off-by: Alejandro Lucero <alucerop@....com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Acked-by: Edward Cree <ecree.xilinx@...il.com>
> ---
>  drivers/net/ethernet/sfc/Kconfig      |  9 +++++
>  drivers/net/ethernet/sfc/Makefile     |  1 +
>  drivers/net/ethernet/sfc/efx.c        | 15 +++++++-
>  drivers/net/ethernet/sfc/efx_cxl.c    | 55 +++++++++++++++++++++++++++
>  drivers/net/ethernet/sfc/efx_cxl.h    | 40 +++++++++++++++++++
>  drivers/net/ethernet/sfc/net_driver.h | 10 +++++
>  6 files changed, 129 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/net/ethernet/sfc/efx_cxl.c
>  create mode 100644 drivers/net/ethernet/sfc/efx_cxl.h
> 
[..]
> +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 efx_cxl *cxl;
> +	u16 dvsec;
> +
> +	probe_data->cxl_pio_initialised = false;
> +
> +	dvsec = pci_find_dvsec_capability(pci_dev, PCI_VENDOR_ID_CXL,
> +					  CXL_DVSEC_PCIE_DEVICE);
> +	if (!dvsec)
> +		return 0;
> +
> +	pci_dbg(pci_dev, "CXL_DVSEC_PCIE_DEVICE capability found\n");
> +
> +	/* Create a cxl_dev_state embedded in the cxl struct using cxl core api
> +	 * specifying no mbox available.
> +	 */
> +	cxl = cxl_dev_state_create(&pci_dev->dev, CXL_DEVTYPE_DEVMEM,
> +				   pci_dev->dev.id, dvsec, struct efx_cxl,
> +				   cxlds, false);
> +
> +	if (!cxl)
> +		return -ENOMEM;
> +
> +	probe_data->cxl = cxl;
> +
> +	return 0;
> +}
> +
> +void efx_cxl_exit(struct efx_probe_data *probe_data)
> +{

So this is empty which means it leaks the cxl_dev_state_create()
allocation, right?

The motivation for the cxl_dev_state_create() macro is so that
you do not need to manage more independently allocated driver objects.
For example, the existing kfree(probe_data) can also free the
cxl_dev_state with a change like below (UNTESTED).

Otherwise, something needs to responsible for freeing 'struct efx_cxl'

-- 8< --
diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index 112e55b98ed3..0135384c6fa1 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -1149,13 +1149,22 @@ static int efx_pci_probe_post_io(struct efx_nic *efx)
 static int efx_pci_probe(struct pci_dev *pci_dev,
 			 const struct pci_device_id *entry)
 {
-	struct efx_probe_data *probe_data, **probe_ptr;
+	struct efx_probe_data *probe_data = NULL, **probe_ptr;
 	struct net_device *net_dev;
 	struct efx_nic *efx;
 	int rc;
 
 	/* Allocate probe data and struct efx_nic */
-	probe_data = kzalloc(sizeof(*probe_data), GFP_KERNEL);
+	dvsec = pci_find_dvsec_capability(pci_dev, PCI_VENDOR_ID_CXL,
+					  CXL_DVSEC_PCIE_DEVICE);
+	if (dvsec) {
+		cxl = cxl_dev_state_create(&pci_dev->dev, CXL_DEVTYPE_DEVMEM,
+					   pci_dev->dev.id, dvsec,
+					   struct efx_probe_data, cxl.cxlds, false);
+		if (cxl)
+			probe_data = container_of(cxl, typeof(*probe_data), cxl.cxlds);
+	} else
+		probe_data = kzalloc(sizeof(*probe_data), GFP_KERNEL);
 	if (!probe_data)
 		return -ENOMEM;
 	probe_data->pci_dev = pci_dev;