linux-kernel - Re: [PATCH v9 02/15] cxl/regs: Prepare for multiple users of register mappings

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Message-ID: <20230829145254.00003259@Huawei.com>
Date:   Tue, 29 Aug 2023 14:52:54 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Terry Bowman <terry.bowman@....com>
CC:     <alison.schofield@...el.com>, <vishal.l.verma@...el.com>,
        <ira.weiny@...el.com>, <bwidawsk@...nel.org>,
        <dan.j.williams@...el.com>, <dave.jiang@...el.com>,
        <linux-cxl@...r.kernel.org>, <rrichter@....com>,
        <linux-kernel@...r.kernel.org>, <bhelgaas@...gle.com>
Subject: Re: [PATCH v9 02/15] cxl/regs: Prepare for multiple users of
 register mappings

On Fri, 25 Aug 2023 18:31:58 -0500
Terry Bowman <terry.bowman@....com> wrote:

> From: Robert Richter <rrichter@....com>
> 
> The function devm_cxl_iomap_block() is used to map register mappings
> of CXL component or device registers. A @dev is used to unmap the IO
> regions during device removal.
> 
> Now, there are multiple devices using the register mappings. E.g. the
> RAS cap of the Component Registers is used by cxl_pci, the HDM cap
> used in cxl_mem. This could cause IO blocks not being freed and a
> subsequent reinitialization to fail if the same device is used for
> both.
> 
> To prevent that, expand cxl_map_component_regs() to pass a @dev to be
> used with devm to IO unmap. This allows to pass the device that
> actually is creating and using the IO region.
> 
> For symmetry also change the function i/f of cxl_map_device_regs().
> 
> Signed-off-by: Robert Richter <rrichter@....com>
> Signed-off-by: Terry Bowman <terry.bowman@....com>

I'm not sure we should leave map->dev around after this change
as it's not obvious where it is valid to use and where it isn't.

Perhaps we just need to pass the device into the few calls
that use it other than the ones you have here.

This patch itself looks fine to me.

Jonathan

> ---
>  drivers/cxl/core/hdm.c  | 3 ++-
>  drivers/cxl/core/regs.c | 4 ++--
>  drivers/cxl/cxl.h       | 2 ++
>  drivers/cxl/pci.c       | 4 ++--
>  4 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 4449b34a80cc..17c8ba8c75e0 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -98,7 +98,8 @@ static int map_hdm_decoder_regs(struct cxl_port *port, void __iomem *crb,
>  		return -ENODEV;
>  	}
>  
> -	return cxl_map_component_regs(&map, regs, BIT(CXL_CM_CAP_CAP_ID_HDM));
> +	return cxl_map_component_regs(&map, &port->dev, regs,
> +				      BIT(CXL_CM_CAP_CAP_ID_HDM));
>  }
>  
>  static bool should_emulate_decoders(struct cxl_endpoint_dvsec_info *info)
> diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c
> index 6281127b3e9d..dfc3e272e7d8 100644
> --- a/drivers/cxl/core/regs.c
> +++ b/drivers/cxl/core/regs.c
> @@ -201,10 +201,10 @@ void __iomem *devm_cxl_iomap_block(struct device *dev, resource_size_t addr,
>  }
>  
>  int cxl_map_component_regs(const struct cxl_register_map *map,
> +			   struct device *dev,
>  			   struct cxl_component_regs *regs,
>  			   unsigned long map_mask)
>  {
> -	struct device *dev = map->dev;
>  	struct mapinfo {
>  		const struct cxl_reg_map *rmap;
>  		void __iomem **addr;
> @@ -235,9 +235,9 @@ int cxl_map_component_regs(const struct cxl_register_map *map,
>  EXPORT_SYMBOL_NS_GPL(cxl_map_component_regs, CXL);
>  
>  int cxl_map_device_regs(const struct cxl_register_map *map,
> +			struct device *dev,
>  			struct cxl_device_regs *regs)
>  {
> -	struct device *dev = map->dev;
>  	resource_size_t phys_addr = map->resource;
>  	struct mapinfo {
>  		const struct cxl_reg_map *rmap;
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 76d92561af29..ec8ba9ebcf64 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -274,9 +274,11 @@ void cxl_probe_component_regs(struct device *dev, void __iomem *base,
>  void cxl_probe_device_regs(struct device *dev, void __iomem *base,
>  			   struct cxl_device_reg_map *map);
>  int cxl_map_component_regs(const struct cxl_register_map *map,
> +			   struct device *dev,
>  			   struct cxl_component_regs *regs,
>  			   unsigned long map_mask);
>  int cxl_map_device_regs(const struct cxl_register_map *map,
> +			struct device *dev,
>  			struct cxl_device_regs *regs);
>  int cxl_map_pmu_regs(struct pci_dev *pdev, struct cxl_pmu_regs *regs,
>  		     struct cxl_register_map *map);
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index 48f88d96029d..88ddcff8a0b2 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -827,7 +827,7 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  	if (rc)
>  		return rc;
>  
> -	rc = cxl_map_device_regs(&map, &cxlds->regs.device_regs);
> +	rc = cxl_map_device_regs(&map, cxlds->dev, &cxlds->regs.device_regs);
>  	if (rc)
>  		return rc;
>  
> @@ -844,7 +844,7 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  
>  	cxlds->component_reg_phys = map.resource;
>  
> -	rc = cxl_map_component_regs(&map, &cxlds->regs.component,
> +	rc = cxl_map_component_regs(&map, cxlds->dev, &cxlds->regs.component,
>  				    BIT(CXL_CM_CAP_CAP_ID_RAS));
>  	if (rc)
>  		dev_dbg(&pdev->dev, "Failed to map RAS capability.\n");