> -----Original Message-----
> From: Julien Grall <jul...@xen.org>
> Sent: 16 October 2020 16:55
> To: Paul Durrant <p...@xen.org>; xen-devel@lists.xenproject.org
> Cc: Paul Durrant <pdurr...@amazon.com>; Ian Jackson <i...@xenproject.org>;
> Wei Liu <w...@xen.org>; Andrew
> Cooper <andrew.coop...@citrix.com>; George Dunlap <george.dun...@citrix.com>;
> Jan Beulich
> <jbeul...@suse.com>; Stefano Stabellini <sstabell...@kernel.org>; Anthony
> PERARD
> <anthony.per...@citrix.com>; Volodymyr Babchuk <volodymyr_babc...@epam.com>;
> Roger Pau Monné
> <roger....@citrix.com>
> Subject: Re: [PATCH 3/5] libxl / iommu / domctl: introduce
> XEN_DOMCTL_IOMMU_SET_ALLOCATION...
>
> Hi Paul,
>
> On 05/10/2020 10:49, Paul Durrant wrote:
> > From: Paul Durrant <pdurr...@amazon.com>
> >
> > ... sub-operation of XEN_DOMCTL_iommu_ctl.
> >
> > This patch adds a new sub-operation into the domctl. The code in iommu_ctl()
> > is extended to call a new arch-specific iommu_set_allocation() function
> > which
> > will be called with the IOMMU page-table overhead (in 4k pages) in response
>
> Why 4KB? Wouldn't it be better to use the hypervisor page size instead?
>
I think I'll follow the shadow/hap code more closely and just pass a value in
MB, then any issue with page size is left inside Xen.
> > diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
> > index 75e855625a..6402678838 100644
> > --- a/xen/include/public/domctl.h
> > +++ b/xen/include/public/domctl.h
> > @@ -1138,8 +1138,16 @@ struct xen_domctl_vuart_op {
> >
> > #define XEN_DOMCTL_IOMMU_INVALID 0
> >
> > +#define XEN_DOMCTL_IOMMU_SET_ALLOCATION 1
> > +struct xen_domctl_iommu_set_allocation {
> > + uint32_t nr_pages;
>
> Shouldn't this be a 64-bit value?
If I pass the value in MB then 32-bits will cover it, I think. I do need to add
padding though.
Paul
>
> Cheers,
>
> --
> Julien Grall
