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Re: [PATCH V2] libxl/arm: Create specific IOMMU node to be referred by virtio-mmio device
- To: Stefano Stabellini <sstabellini@xxxxxxxxxx>
- From: Oleksandr <olekstysh@xxxxxxxxx>
- Date: Thu, 2 Jun 2022 22:28:03 +0300
- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>, Wei Liu <wl@xxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Julien Grall <julien@xxxxxxx>
- Delivery-date: Thu, 02 Jun 2022 19:28:08 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 01.06.22 23:39, Stefano Stabellini wrote:
Hello Stefano
On Wed, 1 Jun 2022, Oleksandr wrote:
On 01.06.22 04:04, Stefano Stabellini wrote:
On Tue, 31 May 2022, Oleksandr Tyshchenko wrote:
From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
Reuse generic IOMMU device tree bindings to communicate Xen specific
information for the virtio devices for which the restricted memory
access using Xen grant mappings need to be enabled.
Insert "iommus" property pointed to the IOMMU node with "xen,grant-dma"
compatible to all virtio devices which backends are going to run in
non-hardware domains (which are non-trusted by default).
Based on device-tree binding from Linux:
Documentation/devicetree/bindings/iommu/xen,grant-dma.yaml
The example of generated nodes:
xen_iommu {
compatible = "xen,grant-dma";
#iommu-cells = <0x01>;
phandle = <0xfde9>;
};
virtio@2000000 {
compatible = "virtio,mmio";
reg = <0x00 0x2000000 0x00 0x200>;
interrupts = <0x00 0x01 0xf01>;
interrupt-parent = <0xfde8>;
dma-coherent;
iommus = <0xfde9 0x01>;
};
virtio@2000200 {
compatible = "virtio,mmio";
reg = <0x00 0x2000200 0x00 0x200>;
interrupts = <0x00 0x02 0xf01>;
interrupt-parent = <0xfde8>;
dma-coherent;
iommus = <0xfde9 0x01>;
};
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
---
!!! This patch is based on non upstreamed yet “Virtio support for
toolstack
on Arm” V8 series which is on review now:
https://lore.kernel.org/xen-devel/1651598763-12162-1-git-send-email-olekstysh@xxxxxxxxx/
New device-tree binding (commit #5) is a part of solution to restrict
memory
access under Xen using xen-grant DMA-mapping layer (which is also on
review):
https://lore.kernel.org/xen-devel/1653944417-17168-1-git-send-email-olekstysh@xxxxxxxxx/
Changes RFC -> V1:
- update commit description
- rebase according to the recent changes to
"libxl: Introduce basic virtio-mmio support on Arm"
Changes V1 -> V2:
- Henry already gave his Reviewed-by, I dropped it due to the changes
- use generic IOMMU device tree bindings instead of custom property
"xen,dev-domid"
- change commit subject and description, was
"libxl/arm: Insert "xen,dev-domid" property to virtio-mmio device
node"
---
tools/libs/light/libxl_arm.c | 49
++++++++++++++++++++++++++++++++---
xen/include/public/device_tree_defs.h | 1 +
2 files changed, 47 insertions(+), 3 deletions(-)
diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
index 9be9b2a..72da3b1 100644
--- a/tools/libs/light/libxl_arm.c
+++ b/tools/libs/light/libxl_arm.c
@@ -865,9 +865,32 @@ static int make_vpci_node(libxl__gc *gc, void *fdt,
return 0;
}
+static int make_xen_iommu_node(libxl__gc *gc, void *fdt)
+{
+ int res;
+
+ /* See Linux
Documentation/devicetree/bindings/iommu/xen,grant-dma.yaml */
+ res = fdt_begin_node(fdt, "xen_iommu");
+ if (res) return res;
+
+ res = fdt_property_compat(gc, fdt, 1, "xen,grant-dma");
+ if (res) return res;
+
+ res = fdt_property_cell(fdt, "#iommu-cells", 1);
+ if (res) return res;
+
+ res = fdt_property_cell(fdt, "phandle", GUEST_PHANDLE_IOMMU);
+ if (res) return res;
+
+ res = fdt_end_node(fdt);
+ if (res) return res;
+
+ return 0;
+}
static int make_virtio_mmio_node(libxl__gc *gc, void *fdt,
- uint64_t base, uint32_t irq)
+ uint64_t base, uint32_t irq,
+ uint32_t backend_domid)
{
int res;
gic_interrupt intr;
@@ -890,6 +913,16 @@ static int make_virtio_mmio_node(libxl__gc *gc, void
*fdt,
res = fdt_property(fdt, "dma-coherent", NULL, 0);
if (res) return res;
+ if (backend_domid != LIBXL_TOOLSTACK_DOMID) {
+ uint32_t iommus_prop[2];
+
+ iommus_prop[0] = cpu_to_fdt32(GUEST_PHANDLE_IOMMU);
+ iommus_prop[1] = cpu_to_fdt32(backend_domid);
+
+ res = fdt_property(fdt, "iommus", iommus_prop,
sizeof(iommus_prop));
+ if (res) return res;
+ }
+
res = fdt_end_node(fdt);
if (res) return res;
@@ -1097,6 +1130,7 @@ static int libxl__prepare_dtb(libxl__gc *gc,
libxl_domain_config *d_config,
size_t fdt_size = 0;
int pfdt_size = 0;
libxl_domain_build_info *const info = &d_config->b_info;
+ bool iommu_created;
unsigned int i;
const libxl_version_info *vers;
@@ -1204,11 +1238,20 @@ next_resize:
if (d_config->num_pcidevs)
FDT( make_vpci_node(gc, fdt, ainfo, dom) );
+ iommu_created = false;
for (i = 0; i < d_config->num_disks; i++) {
libxl_device_disk *disk = &d_config->disks[i];
- if (disk->specification == LIBXL_DISK_SPECIFICATION_VIRTIO)
- FDT( make_virtio_mmio_node(gc, fdt, disk->base,
disk->irq) );
+ if (disk->specification == LIBXL_DISK_SPECIFICATION_VIRTIO) {
+ if (disk->backend_domid != LIBXL_TOOLSTACK_DOMID &&
+ !iommu_created) {
+ FDT( make_xen_iommu_node(gc, fdt) );
+ iommu_created = true;
+ }
+
+ FDT( make_virtio_mmio_node(gc, fdt, disk->base,
disk->irq,
+ disk->backend_domid) );
+ }
This is a matter of taste as the code would also work as is, but I would
do the following instead:
if ( d_config->num_disks > 0 &&
disk->backend_domid != LIBXL_TOOLSTACK_DOMID) {
FDT( make_xen_iommu_node(gc, fdt) );
}
for (i = 0; i < d_config->num_disks; i++) {
libxl_device_disk *disk = &d_config->disks[i];
if (disk->specification == LIBXL_DISK_SPECIFICATION_VIRTIO)
FDT( make_virtio_mmio_node(gc, fdt, disk->base, disk->irq) );
}
I got your idea to avoid using local "iommu_created". For that, I think, we
need to modify the first check to make sure that we have at least one virtio
device, otherwise we might end up inserting unused IOMMU node. But, it will
turn into an extra loop to go through num_disks and look for
LIBXL_DISK_SPECIFICATION_VIRTIO.
I see, then just keep it as is.
ok
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Thanks!
--
Regards,
Oleksandr Tyshchenko
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