linux-kernel - Re: [PATCH 02/15] cxl/core: Check physical address before mapping it in devm_cxl_iomap

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Date:   Wed, 31 Aug 2022 09:56:51 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Robert Richter <rrichter@....com>
CC:     Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>
Subject: Re: [PATCH 02/15] cxl/core: Check physical address before mapping
 it in devm_cxl_iomap_block()

On Wed, 31 Aug 2022 10:15:50 +0200
Robert Richter <rrichter@....com> wrote:

> The physical base address of a CXL range can be invalid and is then
> set to CXL_RESOURCE_NONE. Early check this case before mapping a
> memory block in devm_cxl_iomap_block().

An example of when it is invalid would be a useful addition
to this description.  Feels to me like this is papering over the cracks
in something we should have ruled out earlier in the flow.

Jonathan

> 
> Signed-off-by: Robert Richter <rrichter@....com>
> ---
>  drivers/cxl/core/regs.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c
> index 39a129c57d40..f216c017a474 100644
> --- a/drivers/cxl/core/regs.c
> +++ b/drivers/cxl/core/regs.c
> @@ -165,6 +165,9 @@ void __iomem *devm_cxl_iomap_block(struct device *dev, resource_size_t addr,
>  	void __iomem *ret_val;
>  	struct resource *res;
>  
> +	if (addr == CXL_RESOURCE_NONE)
> +		return NULL;
> +
>  	res = devm_request_mem_region(dev, addr, length, dev_name(dev));
>  	if (!res) {
>  		resource_size_t end = addr + length - 1;