> -----Original Message-----
> From: Xen-devel <xen-devel-boun...@lists.xenproject.org> On Behalf Of
> Rahul Singh
> Sent: 2022年1月14日 16:22
> To: Sergiy Kibrik <sergiy_kib...@epam.com>
> Cc: xen-devel <xen-devel@lists.xenproject.org>; Stefano Stabellini
> <sstabell...@kernel.org>; Julien Grall <jul...@xen.org>; Oleksandr
> Tyshchenko <olekst...@gmail.com>; Andrii Anisov
> <andrii_ani...@epam.com>
> 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_kib...@epam.com>
> 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_kib...@epam.com>
>
> Reviewed-by: Rahul Singh <rahul.si...@arm.com>
>
> Regards,
> Rahul
> > ---
> > Cc: Stefano Stabellini <sstabell...@kernel.org>
> > Cc: Julien Grall <jul...@xen.org>
> > Cc: Oleksandr Tyshchenko <olekst...@gmail.com>
> > Cc: Andrii Anisov <andrii_ani...@epam.com>
> >
> >
> > 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
> >
> >
>
