Subject: Re: [PATCH v7 04/28] cxl/pci: add check for validating capabilities

From: Zhi Wang <[email-masked]>
Date: Wed, 11 Dec 2024 21:20:28 +0200

On Mon, 9 Dec 2024 18:54:05 +0000
<[email-masked]> wrote:

Reviewed-by: Zhi Wang <[email-masked]>

> From: Alejandro Lucero <[email-masked]>
> 
> During CXL device initialization supported capabilities by the device
> are discovered. Type3 and Type2 devices have different mandatory
> capabilities and a Type2 expects a specific set including optional
> capabilities.
> 
> Add a function for checking expected capabilities against those found
> during initialization and allow those mandatory/expected capabilities to
> be a subset of the capabilities found.
> 
> Rely on this function for validating capabilities instead of when CXL
> regs are probed.
> 
> Signed-off-by: Alejandro Lucero <[email-masked]>
> ---
>  drivers/cxl/core/pci.c  | 16 ++++++++++++++++
>  drivers/cxl/core/regs.c |  9 ---------
>  drivers/cxl/pci.c       | 24 ++++++++++++++++++++++++
>  include/cxl/cxl.h       |  3 +++
>  4 files changed, 43 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index c07651cd8f3d..bc098b2ce55d 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -8,6 +8,7 @@
>  #include <linux/pci.h>
>  #include <linux/pci-doe.h>
>  #include <linux/aer.h>
> +#include <cxl/cxl.h>
>  #include <cxlpci.h>
>  #include <cxlmem.h>
>  #include <cxl.h>
> @@ -1055,3 +1056,18 @@ int cxl_pci_get_bandwidth(struct pci_dev *pdev, struct access_coordinate *c)
>  
>  	return 0;
>  }
> +
> +bool cxl_pci_check_caps(struct cxl_dev_state *cxlds, unsigned long *expected_caps,
> +			unsigned long *current_caps)
> +{
> +
> +	if (current_caps)
> +		bitmap_copy(current_caps, cxlds->capabilities, CXL_MAX_CAPS);
> +
> +	dev_dbg(cxlds->dev, "Checking cxlds caps 0x%08lx vs expected caps 0x%08lx\n",
> +		*cxlds->capabilities, *expected_caps);
> +
> +	/* Checking a minimum of mandatory/expected capabilities */
> +	return bitmap_subset(expected_caps, cxlds->capabilities, CXL_MAX_CAPS);
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_pci_check_caps, "CXL");
> diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c
> index ac3a27c6e442..deaf18be896d 100644
> --- a/drivers/cxl/core/regs.c
> +++ b/drivers/cxl/core/regs.c
> @@ -446,15 +446,6 @@ static int cxl_probe_regs(struct cxl_register_map *map, unsigned long *caps)
>  	case CXL_REGLOC_RBI_MEMDEV:
>  		dev_map = &map->device_map;
>  		cxl_probe_device_regs(host, base, dev_map, caps);
> -		if (!dev_map->status.valid || !dev_map->mbox.valid ||
> -		    !dev_map->memdev.valid) {
> -			dev_err(host, "registers not found: %s%s%s\n",
> -				!dev_map->status.valid ? "status " : "",
> -				!dev_map->mbox.valid ? "mbox " : "",
> -				!dev_map->memdev.valid ? "memdev " : "");
> -			return -ENXIO;
> -		}
> -
>  		dev_dbg(host, "Probing device registers...\n");
>  		break;
>  	default:
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index dbc1cd9bec09..1fcc53df1217 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -903,6 +903,8 @@ __ATTRIBUTE_GROUPS(cxl_rcd);
>  static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  {
>  	struct pci_host_bridge *host_bridge = pci_find_host_bridge(pdev->bus);
> +	DECLARE_BITMAP(expected, CXL_MAX_CAPS);
> +	DECLARE_BITMAP(found, CXL_MAX_CAPS);
>  	struct cxl_memdev_state *mds;
>  	struct cxl_dev_state *cxlds;
>  	struct cxl_register_map map;
> @@ -964,6 +966,28 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  	if (rc)
>  		dev_dbg(&pdev->dev, "Failed to map RAS capability.\n");
>  
> +	bitmap_clear(expected, 0, CXL_MAX_CAPS);
> +
> +	/*
> +	 * These are the mandatory capabilities for a Type3 device.
> +	 * Only checking capabilities used by current Linux drivers.
> +	 */
> +	bitmap_set(expected, CXL_DEV_CAP_HDM, 1);
> +	bitmap_set(expected, CXL_DEV_CAP_DEV_STATUS, 1);
> +	bitmap_set(expected, CXL_DEV_CAP_MAILBOX_PRIMARY, 1);
> +	bitmap_set(expected, CXL_DEV_CAP_MEMDEV, 1);
> +
> +	/*
> +	 * Checking mandatory caps are there as, at least, a subset of those
> +	 * found.
> +	 */
> +	if (!cxl_pci_check_caps(cxlds, expected, found)) {
> +		dev_err(&pdev->dev,
> +			"Expected mandatory capabilities not found: (%08lx - %08lx)\n",
> +			*expected, *found);
> +		return -ENXIO;
> +	}
> +
>  	rc = cxl_pci_type3_init_mailbox(cxlds);
>  	if (rc)
>  		return rc;
> diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
> index f656fcd4945f..05f06bfd2c29 100644
> --- a/include/cxl/cxl.h
> +++ b/include/cxl/cxl.h
> @@ -37,4 +37,7 @@ void cxl_set_dvsec(struct cxl_dev_state *cxlds, u16 dvsec);
>  void cxl_set_serial(struct cxl_dev_state *cxlds, u64 serial);
>  int cxl_set_resource(struct cxl_dev_state *cxlds, struct resource res,
>  		     enum cxl_resource);
> +bool cxl_pci_check_caps(struct cxl_dev_state *cxlds,
> +			unsigned long *expected_caps,
> +			unsigned long *current_caps);
>  #endif