> -----Original Message-----
> From: Jan Beulich <jbeul...@suse.com>
> Sent: 19 October 2020 08:30
> To: p...@xen.org
> Cc: 'Julien Grall' <jul...@xen.org>; xen-devel@lists.xenproject.org; 'Paul
> Durrant'
> <pdurr...@amazon.com>; 'Daniel De Graaf' <dgde...@tycho.nsa.gov>; 'Ian
> Jackson' <i...@xenproject.org>;
> 'Wei Liu' <w...@xen.org>; 'Andrew Cooper' <andrew.coop...@citrix.com>;
> 'George Dunlap'
> <george.dun...@citrix.com>; 'Stefano Stabellini' <sstabell...@kernel.org>
> Subject: Re: [PATCH 2/5] iommu / domctl: introduce XEN_DOMCTL_iommu_ctl
>
> On 19.10.2020 09:23, Paul Durrant wrote:
> >> From: Julien Grall <jul...@xen.org>
> >> Sent: 16 October 2020 16:47
> >>
> >> On 05/10/2020 10:49, Paul Durrant wrote:
> >>> diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
> >>> index 791f0a2592..75e855625a 100644
> >>> --- a/xen/include/public/domctl.h
> >>> +++ b/xen/include/public/domctl.h
> >>> @@ -1130,6 +1130,18 @@ struct xen_domctl_vuart_op {
> >>> */
> >>> };
> >>>
> >>> +/*
> >>> + * XEN_DOMCTL_iommu_ctl
> >>> + *
> >>> + * Control of VM IOMMU settings
> >>> + */
> >>> +
> >>> +#define XEN_DOMCTL_IOMMU_INVALID 0
> >>
> >> I can't find any user of XEN_DOMCTL_IOMMU_INVALID. What's the purpose
> >> for it?
> >>
> >
> > It's just a placeholder. I think it's generally safer that a zero opcode
> > value is invalid.
>
> But does this then need a #define? Starting valid command from 1
> ought to be sufficient?
>
Seems harmless enough, and it also seemed the best way since to reserve 0 since
this patch doesn't actually introduce any ops. As it has caused so much
controversy though, I'll remove it.
Paul
> Jan
