Re: [Xen-devel] [PATCH 3/4] xen/public: Document HYPERCALL_console_io()

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 09/04/2019 12:42, Jan Beulich wrote:
> > > > On 09.04.19 at 13:26, <julien.grall@xxxxxxx> wrote:
> > On 03/04/2019 14:04, Jan Beulich wrote:
> > > Also please note the quotation used by the mentioned
> > > existing doc comments, as well as a few other formal aspects
> > > (like them also making clear what the return type is). I think
> > > that's a model used elsewhere as well, so I think you should
> > > follow it here.
> > I haven't replicated the ` because I have no idea what they are used for. I
> > would appreciate if you provide pointer how to use them.
> Well, I can only point you at the history of things, e.g.
> 262e118a37 "docs/html/: Annotations for two hypercalls".
>
> > > The other thing is: As mentioned elsewhere, I don't think the
> > > first two parameters should be plain int. I'm not happy to see
> > > this proliferate into documentation as well, i.e. I'd prefer if
> > > this was corrected before adding documentation. Would you
> > > be willing to do this, or should I add it to my todo list?
> > While switching from cmd from signed to unsigned should be ok. This would
> > introduce a different behavior of for count.
> Since this removes an error condition, I think this is an okay change
> to happen, without ...
>
> > Are we happy with that, or shall we add a check ((int)count) > 0?
> ... any such extra check. This also isn't going to introduce any new
> real risk of a long running operation or some such - if 2Gb of input
> data are fine, I can't see why 4Gb wouldn't be, too.
Actually, it will not be fine at least for the read case. The return value is a 
32-bit value (on AArch32 and if you want to keep compat between 64-bit and 
32-bit). A negative value indicates an error. As we return the number of 
characters read, it means we can only handle 2GB.
So I would rather limit the buffer to 2GB for everyone.

Cheers,

--
Julien Grall

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