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Date:   Mon, 1 Feb 2021 08:53:52 -0800
From:   Ben Widawsky <ben.widawsky@intel.com>
To:     David Rientjes <rientjes@google.com>
Cc:     linux-cxl@vger.kernel.org, linux-acpi@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org,
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Subject: Re: [PATCH 03/14] cxl/mem: Find device capabilities
Message-ID: <20210201165352.wi7tzpnd4ymxlms4@intel.com>
References: <20210130002438.1872527-1-ben.widawsky@intel.com>
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On 21-01-30 15:51:49, David Rientjes wrote:
> On Fri, 29 Jan 2021, Ben Widawsky wrote:
> 
> > +static int cxl_mem_setup_mailbox(struct cxl_mem *cxlm)
> > +{
> > +	const int cap = cxl_read_mbox_reg32(cxlm, CXLDEV_MB_CAPS_OFFSET);
> > +
> > +	cxlm->mbox.payload_size =
> > +		1 << CXL_GET_FIELD(cap, CXLDEV_MB_CAP_PAYLOAD_SIZE);
> > +
> > +	/* 8.2.8.4.3 */
> > +	if (cxlm->mbox.payload_size < 256) {
> > +		dev_err(&cxlm->pdev->dev, "Mailbox is too small (%zub)",
> > +			cxlm->mbox.payload_size);
> > +		return -ENXIO;
> > +	}
> 
> Any reason not to check cxlm->mbox.payload_size > (1 << 20) as well and 
> return ENXIO if true?

If some crazy vendor wanted to ship a mailbox larger than 1M, why should the
driver not allow it?

I'm open to changing it, it just seems like a larger mailbox wouldn't be fatal.