RE: [XEN PATCH v3] xen/arm: introduce dummy iommu node for dom0

[Jiamei Xie <Jiamei.Xie@xxxxxxx>]

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of
> Rahul Singh
> Sent: 2022年1月14日 16:22
> To: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>
> Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>; Stefano Stabellini
> <sstabellini@xxxxxxxxxx>; Julien Grall <julien@xxxxxxx>; Oleksandr
> Tyshchenko <olekstysh@xxxxxxxxx>; Andrii Anisov
> <Andrii_Anisov@xxxxxxxx>
> Subject: Re: [XEN PATCH v3] xen/arm: introduce dummy iommu node for
> dom0
> 
> Hi,
> 
> > On 11 Jan 2022, at 11:26 am, Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>
> wrote:
> >
> > Currently no IOMMU properties are exposed to dom0, thus kernel by
> default
> > assumes no protection and enables swiotlb-xen, which leads to costly and
> > unnecessary buffers bouncing.
> >
> > To let kernel know which device is behing IOMMU and hence needs no
[Jiamei Xie] 
behing?  Typo

Best wishes
Jiamei Xie


> swiotlb
> > services we introduce dummy xen-iommu node in FDT and link protected
> device
> > nodes to it, using here device tree iommu bindings.
> >
> > Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>
> 
> Reviewed-by: Rahul Singh <rahul.singh@xxxxxxx>
> 
> Regards,
> Rahul
> > ---
> > Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> > Cc: Julien Grall <julien@xxxxxxx>
> > Cc: Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>
> > Cc: Andrii Anisov <Andrii_Anisov@xxxxxxxx>
> >
> >
> > Changelog:
> >
> > v3: rebased over staging & remove redundand phandle_iommu attribute,
> discussion:
> >     https://lists.xenproject.org/archives/html/xen-devel/2021-
> 12/msg01753.html
> >
> > v2: re-use common iommu dt bindings to let guests know which devices
> are protected:
> >     https://lists.xenproject.org/archives/html/xen-devel/2021-
> 10/msg00073.html
> >
> > xen/arch/arm/domain_build.c           | 42
> +++++++++++++++++++++++++++
> > xen/include/public/device_tree_defs.h |  1 +
> > 2 files changed, 43 insertions(+)
> >
> > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> > index 6931c022a2..b82ba72fac 100644
> > --- a/xen/arch/arm/domain_build.c
> > +++ b/xen/arch/arm/domain_build.c
> > @@ -845,6 +845,12 @@ static int __init write_properties(struct domain *d,
> struct kernel_info *kinfo,
> >         }
> >     }
> >
> > +    if ( iommu_node && is_iommu_enabled(d) &&
> dt_device_is_protected(node) )
> > +    {
> > +        res = fdt_property_cell(kinfo->fdt, "iommus",
> GUEST_PHANDLE_IOMMU);
> > +        if ( res )
> > +            return res;
> > +    }
> >     return 0;
> > }
> >
> > @@ -1479,6 +1485,38 @@ static int __init make_cpus_node(const struct
> domain *d, void *fdt)
> >     return res;
> > }
> >
> > +static int __init make_iommu_node(const struct domain *d,
> > +                                  const struct kernel_info *kinfo)
> > +{
> > +    const char compat[] = "xen,iommu-el2-v1";
> > +    int res;
> > +
> > +    if ( !is_iommu_enabled(d) )
> > +        return 0;
> > +
> > +    dt_dprintk("Create iommu node\n");
> > +
> > +    res = fdt_begin_node(kinfo->fdt, "xen-iommu");
> > +    if ( res )
> > +        return res;
> > +
> > +    res = fdt_property(kinfo->fdt, "compatible", compat, sizeof(compat));
> > +    if ( res )
> > +        return res;
> > +
> > +    res = fdt_property_cell(kinfo->fdt, "#iommu-cells", 0);
> > +    if ( res )
> > +        return res;
> > +
> > +    res = fdt_property_cell(kinfo->fdt, "phandle",
> GUEST_PHANDLE_IOMMU);
> > +
> > +    res = fdt_end_node(kinfo->fdt);
> > +    if ( res )
> > +        return res;
> > +
> > +    return res;
> > +}
> > +
> > static int __init make_gic_node(const struct domain *d, void *fdt,
> >                                 const struct dt_device_node *node)
> > {
> > @@ -2127,6 +2165,10 @@ static int __init handle_node(struct domain *d,
> struct kernel_info *kinfo,
> >         if ( res )
> >             return res;
> >
> > +        res = make_iommu_node(d, kinfo);
> > +        if ( res )
> > +            return res;
> > +
> >         res = make_memory_node(d, kinfo->fdt, addrcells, sizecells, &kinfo-
> >mem);
> >         if ( res )
> >             return res;
> > diff --git a/xen/include/public/device_tree_defs.h
> b/xen/include/public/device_tree_defs.h
> > index 209d43de3f..df58944bd0 100644
> > --- a/xen/include/public/device_tree_defs.h
> > +++ b/xen/include/public/device_tree_defs.h
> > @@ -7,6 +7,7 @@
> >  * onwards. Reserve a high value for the GIC phandle.
> >  */
> > #define GUEST_PHANDLE_GIC (65000)
> > +#define GUEST_PHANDLE_IOMMU (GUEST_PHANDLE_GIC + 1)
> >
> > #define GUEST_ROOT_ADDRESS_CELLS 2
> > #define GUEST_ROOT_SIZE_CELLS 2
> > --
> > 2.25.1
> >
> >
>