Re: hypercalls with 64-bit results

[Juergen Gross <jgross@xxxxxxxx>]

On 17.06.21 10:00, Jan Beulich wrote:
> On 17.06.2021 06:55, Juergen Gross wrote:
> > On 16.06.21 18:04, Jan Beulich wrote:
> > > Since hypercalls from the tool stack are based on ioctl(), and since
> > > ioctl() has a return type of "int", I'm afraid there's no way we can
> > > deal with this by adjusting function return types in the libraries.
> > > Instead we appear to need either a new privcmd ioctl or new XENMEM_*
> > > subops (for those cases where potentially large values get returned).
> > I think we can just use a multicall in libxc to wrap the affected
> > operations.
> Hmm, we might, if we're happy for these to then not work in HVM domains
> (PVH Dom0, which still is experimental only, or PVH/HVM DomU-s using
> the libraries for some purpose), or if we finally wire up multicalls in
> the HVM case (there ought to be a reason why they aren't, but I have no
> idea what that is).
Me neither, especially as on Arm they are supported.

And TBH: PVH Dom0 without multicalls might be hard anyway.


Juergen

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