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

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Date:   Thu, 1 Sep 2022 07:31:14 +0200
From:   Robert Richter <rrichter@....com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.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 31.08.22 09:56:51, Jonathan Cameron wrote:
> 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.

IIRC this happened during code development in cxl_pci_probe() when
cxl_map_regs() is called but the base addr was not determined
correctly before. It's similar to a NULL pointer check.

-Robert