linux-kernel - Re: [PATCH v2 2/5] cxl/mem: Reserve all device regions at once

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Date:   Tue, 25 May 2021 10:54:00 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     <ira.weiny@...el.com>
CC:     Ben Widawsky <ben.widawsky@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/5] cxl/mem: Reserve all device regions at once

On Fri, 21 May 2021 17:11:51 -0700
<ira.weiny@...el.com> wrote:

> From: Ira Weiny <ira.weiny@...el.com>
> 
> In order to remap individual register sets each bar region must be
> reserved prior to mapping.  Because the details of individual register
> sets are contained within the BARs themselves, the bar must be mapped 2
> times, once to extract this information and a second time for each
> register set.
> 
> Rather than attempt to reserve each BAR individually and track if that
> bar has been reserved.  Open code pcim_iomap_regions() by first
> reserving all memory regions on the device and then mapping the bars
> individually as needed.
> 
> NOTE pci_request_mem_regions() does not need a corresponding
> pci_release_mem_regions() because the pci device is managed via
> pcim_enable_device().
> 
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> 
> ---
> Changes for V2:
> 	Rebased on https://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl.git/commit/?h=pending
> 	Clarify why pci_release_mem_regions() does not need to be
> 	called.

Gah - I'm never keen on hidden automated cleanup.  Oh well.

> 	Adjust for the different return code between pcim_iomap_regions() and
> 	pcim_iomap()
> 	Change print specifier.
> ---
>  drivers/cxl/pci.c | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index b2f978954daa..33fc6e1634e3 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -927,7 +927,7 @@ static void __iomem *cxl_mem_map_regblock(struct cxl_mem *cxlm,
>  {
>  	struct pci_dev *pdev = cxlm->pdev;
>  	struct device *dev = &pdev->dev;
> -	int rc;
> +	void __iomem *addr;
>  
>  	/* Basic sanity check that BAR is big enough */
>  	if (pci_resource_len(pdev, bar) < offset) {
> @@ -936,13 +936,14 @@ static void __iomem *cxl_mem_map_regblock(struct cxl_mem *cxlm,
>  		return IOMEM_ERR_PTR(-ENXIO);
>  	}
>  
> -	rc = pcim_iomap_regions(pdev, BIT(bar), pci_name(pdev));
> -	if (rc) {
> +	addr = pcim_iomap(pdev, bar, 0);
> +	if (!addr) {
>  		dev_err(dev, "failed to map registers\n");
> -		return IOMEM_ERR_PTR(rc);
> +		return addr;
>  	}
>  
> -	dev_dbg(dev, "Mapped CXL Memory Device resource\n");
> +	dev_dbg(dev, "Mapped CXL Memory Device resource bar %u @ %#llx\n",
> +		bar, offset);
>  
>  	return pcim_iomap_table(pdev)[bar] + offset;
>  }
> @@ -1003,6 +1004,9 @@ static int cxl_mem_setup_regs(struct cxl_mem *cxlm)
>  		return -ENXIO;
>  	}
>  
> +	if (pci_request_mem_regions(pdev, pci_name(pdev)))
> +		return -ENODEV;
> +
>  	/* Get the size of the Register Locator DVSEC */
>  	pci_read_config_dword(pdev, regloc + PCI_DVSEC_HEADER1, &regloc_size);
>  	regloc_size = FIELD_GET(PCI_DVSEC_HEADER1_LENGTH_MASK, regloc_size);
> @@ -1028,8 +1032,8 @@ static int cxl_mem_setup_regs(struct cxl_mem *cxlm)
>  
>  		if (reg_type == CXL_REGLOC_RBI_MEMDEV) {
>  			base = cxl_mem_map_regblock(cxlm, bar, offset);
> -			if (IS_ERR(base))
> -				return PTR_ERR(base);
> +			if (!base)
> +				return -ENOMEM;
>  			break;
>  		}
>  	}