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Message-ID: <20210202001120.vr6mos7ylnbqytxh@intel.com> Date: Mon, 1 Feb 2021 16:11:20 -0800 From: Ben Widawsky <ben.widawsky@...el.com> To: David Rientjes <rientjes@...gle.com> Cc: linux-cxl@...r.kernel.org, linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org, linux-pci@...r.kernel.org, Bjorn Helgaas <helgaas@...nel.org>, Chris Browy <cbrowy@...ry-design.com>, Christoph Hellwig <hch@...radead.org>, Dan Williams <dan.j.williams@...el.com>, Ira Weiny <ira.weiny@...el.com>, Jon Masters <jcm@...masters.org>, Jonathan Cameron <Jonathan.Cameron@...wei.com>, Rafael Wysocki <rafael.j.wysocki@...el.com>, Randy Dunlap <rdunlap@...radead.org>, Vishal Verma <vishal.l.verma@...el.com>, daniel.lll@...baba-inc.com, "John Groves (jgroves)" <jgroves@...ron.com>, "Kelley, Sean V" <sean.v.kelley@...el.com> Subject: Re: [PATCH 03/14] cxl/mem: Find device capabilities On 21-02-01 15:58:09, David Rientjes wrote: > On Mon, 1 Feb 2021, Ben Widawsky wrote: > > > > I haven't seen the update to 8.2.8.4.5 to know yet :) > > > > > > You make a good point of at least being able to interact with the driver. > > > I think you could argue that if the driver binds, then the payload size is > > > accepted, in which case it would be strange to get an EINVAL when using > > > the ioctl with anything >1MB. > > > > > > Concern was that if we mask off the reserved bits from the command > > > register that we could be masking part of the payload size that is being > > > passed if the accepted max is >1MB. Idea was to avoid any possibility of > > > this inconsistency. If this is being checked for ioctl, seems like it's > > > checking reserved bits. > > > > > > But maybe I should just wait for the spec update. > > > > Well, I wouldn't hold your breath (it would be an errata in this case anyway). > > My preference would be to just allow allow mailbox payload size to be 2^31 and > > not deal with this. > > > > My question was how strongly do you feel it's an error that should prevent > > binding. > > > > I don't have an objection to binding, but doesn't this require that the > check in cxl_validate_cmd_from_user() guarantees send_cmd->size_in cannot > be greater than 1MB? You're correct. I'd need to add: cxlm->mbox.payload_size = min_t(size_t, 1 << CXL_GET_FIELD(cap, CXLDEV_MB_CAP_PAYLOAD_SIZE), 1<<20)
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