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

David Rientjes
2021-02-01T23:59:28Z

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?