Re: [PATCH 03/14] cxl/mem: Find device capabilities

[David Rientjes]

On Mon, 1 Feb 2021, Ben Widawsky wrote:

> 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?
> 

Because the spec disallows it :)