> -----Original Message-----
> From: Stefano Stabellini [mailto:[email protected]]
> Sent: 03 January 2019 18:20
> To: Andrew Cooper <[email protected]>
> Cc: Stefano Stabellini <[email protected]>; [email protected];
> [email protected]; [email protected]; Paul Durrant
> <[email protected]>
> Subject: Re: [Xen-devel] [PATCH for-4.12] xen/iommu: fix dev assignment on
> ARM after 91d4eca7
>
> On Thu, 3 Jan 2019, Andrew Cooper wrote:
> > On 03/01/2019 00:28, Stefano Stabellini wrote:
> > > Fix device assignment on ARM after 91d4eca7 "mm / iommu: split
> > > need_iommu() into has_iommu_pt() and need_iommu_pt_sync()".
> > >
> > > arch_iommu_populate_page_table returns -ENOSYS which causes
> > > iommu_construct to return early, although it is not an error.
> > >
> > > Interestingly, the if ( rc ) was present even before 91d4eca7, but it
> was
> > > still working before. Now, with the new hd->status field it won't
> > > complete the initialization successfully.
> > >
> > > Signed-off-by: Stefano Stabellini <[email protected]>
> > >
> > > diff --git a/xen/drivers/passthrough/iommu.c
> b/xen/drivers/passthrough/iommu.c
> > > index ac62d7f..a63329b 100644
> > > --- a/xen/drivers/passthrough/iommu.c
> > > +++ b/xen/drivers/passthrough/iommu.c
> > > @@ -269,7 +269,7 @@ int iommu_construct(struct domain *d)
> > > hd->need_sync = true;
> > >
> > > rc = arch_iommu_populate_page_table(d);
> >
> > The comment in ARM's arch_iommu_populate_page_table() says
> >
> > /* The IOMMU shares the p2m with the CPU */
> >
> > Which means that iommu_use_hap_pt() (just out of context above this
> > hunk) is wrong. It should return true, which will prevent us entering
> > this path during initialisation.
>
> iommu_use_hap_pt is implemented by calling has_iommu_pt(d) (also on x86
> is part of the implementation), which is implemented as:
>
> (dom_iommu(d)->status != IOMMU_STATUS_disabled)
>
> IOMMU_STATUS_disabled is zero in the enum, so status starts as
> IOMMU_STATUS_disabled. It is set to IOMMU_STATUS_initializing for dom0
> in iommu_hwdom_init, but it is not set to IOMMU_STATUS_initializing for
> other domains anywhere, leading to this error.
It is set for other domains... see iommu_construct().
Paul
>
> It looks like we want to move the initialization of status from
> iommu_hwdom_init to iommu_domain_init, which is called for everybody.
>
>
> diff --git a/xen/drivers/passthrough/iommu.c
> b/xen/drivers/passthrough/iommu.c
> index ac62d7f..7cf6aaf 100644
> --- a/xen/drivers/passthrough/iommu.c
> +++ b/xen/drivers/passthrough/iommu.c
> @@ -180,6 +180,7 @@ int iommu_domain_init(struct domain *d)
> if ( !iommu_enabled )
> return 0;
>
> + hd->status = IOMMU_STATUS_initializing;
> hd->platform_ops = iommu_get_ops();
> return hd->platform_ops->init(d);
> }
> @@ -206,7 +207,6 @@ void __hwdom_init iommu_hwdom_init(struct domain *d)
>
> register_keyhandler('o', &iommu_dump_p2m_table, "dump iommu p2m
> table", 0);
>
> - hd->status = IOMMU_STATUS_initializing;
> hd->need_sync = iommu_hwdom_strict && !iommu_use_hap_pt(d);
> if ( need_iommu_pt_sync(d) )
> {
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