> -----Original Message-----
> From: Julien Grall <julien.gr...@arm.com>
> Sent: 05 September 2019 20:59
> To: Paul Durrant <paul.durr...@citrix.com>; xen-devel@lists.xenproject.org
> Cc: Jan Beulich <jbeul...@suse.com>; Ian Jackson <ian.jack...@citrix.com>;
> Wei Liu <w...@xen.org>;
> Andrew Cooper <andrew.coop...@citrix.com>; George Dunlap
> <george.dun...@citrix.com>; Konrad Rzeszutek
> Wilk <konrad.w...@oracle.com>; Stefano Stabellini <sstabell...@kernel.org>;
> Tim (Xen.org)
> <t...@xen.org>; Anthony Perard <anthony.per...@citrix.com>; Christian Lindig
> <christian.lin...@citrix.com>; David Scott <d...@recoil.org>; Volodymyr
> Babchuk
> <volodymyr_babc...@epam.com>; Roger Pau Monne <roger....@citrix.com>
> Subject: Re: [PATCH v8 6/6] introduce a 'passthrough' configuration option to
> xl.cfg...
>
> Hi,
>
> On 9/2/19 3:50 PM, Paul Durrant wrote:
> > @@ -263,9 +263,17 @@ struct domain_iommu {
> > DECLARE_BITMAP(features, IOMMU_FEAT_count);
> >
> > /*
> > - * Does the guest reqire mappings to be synchonized, to maintain
> > - * the default dfn == pfn map. (See comment on dfn at the top of
> > - * include/xen/mm.h).
> > + * Does the guest share HAP mapping with the IOMMU? This is always
> > + * true for ARM systems and may be true for x86 systems where the
> > + * the hardware is capable.
> > + */
>
> I am worried that such comment may rot over the time. For instance, if
> we either add a new architecture or decide to stop sharing PT on Arm.
>
> I vaguely recall some potential issues with the MSI doorbells that would
> require us to unshare the PT when they will be supported in guest.
>
> I would suggest to either refers to the implementation of
> iommu_use_hap_pt() or drop completely the second sentence.
Ok, I'll just drop the sentence.
Paul
>
> > + bool hap_pt_share;
> > +
> > + /*
> > + * Does the guest require mappings to be synchronized, to maintain
> > + * the default dfn == pfn map? (See comment on dfn at the top of
> > + * include/xen/mm.h). Note that hap_pt_share == false does not
> > + * necessarily imply this is true.
> > */
> > bool need_sync;
> > };
> > @@ -275,8 +283,7 @@ struct domain_iommu {
> > #define iommu_clear_feature(d, f) clear_bit(f, dom_iommu(d)->features)
> >
> > /* Are we using the domain P2M table as its IOMMU pagetable? */
> > -#define iommu_use_hap_pt(d) \
> > - (hap_enabled(d) && is_iommu_enabled(d) && iommu_hap_pt_share)
> > +#define iommu_use_hap_pt(d) (dom_iommu(d)->hap_pt_share)
> >
> > /* Does the IOMMU pagetable need to be kept synchronized with the P2M */
> > #ifdef CONFIG_HAS_PASSTHROUGH
> >
>
> Cheers,
>
> --
> Julien Grall
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