Re: [PATCH V1 4/6] dt-bindings: Add xen,dev-domid property description for xen-grant DMA ops
From: Oleksandr
Date: Thu May 05 2022 - 06:12:39 EST
On 04.05.22 03:02, Rob Herring wrote:
Hello Rob
On Tue, May 03, 2022 at 08:09:32PM +0300, Oleksandr wrote:
On 03.05.22 00:59, Rob Herring wrote:
Hello Rob
On Fri, Apr 22, 2022 at 07:51:01PM +0300, Oleksandr Tyshchenko wrote:
From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
Introduce Xen specific binding for the virtualized device (e.g. virtio)
to be used by Xen grant DMA-mapping layer in the subsequent commit.
This binding indicates that Xen grant mappings scheme needs to be
enabled for the device which DT node contains that property and specifies
the ID of Xen domain where the corresponding backend resides. The ID
(domid) is used as an argument to the grant mapping APIs.
This is needed for the option to restrict memory access using Xen grant
mappings to work which primary goal is to enable using virtio devices
in Xen guests.
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
---
Changes RFC -> V1:
- update commit subject/description and text in description
- move to devicetree/bindings/arm/
---
.../devicetree/bindings/arm/xen,dev-domid.yaml | 37 ++++++++++++++++++++++
1 file changed, 37 insertions(+)
create mode 100644 Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
diff --git a/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
new file mode 100644
index 00000000..ef0f747
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: (GPL-2.0-only or BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/xen,dev-domid.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Xen specific binding for the virtualized device (e.g. virtio)
+
+maintainers:
+ - Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
+
+select: true
Do we really need to support this property everywhere?
From my understanding - yes.
As, I think, any device node describing virtulized device in the guest
device tree can have this property. Initially (in the RFC series) the
"solution to restrict memory access using Xen grant mappings" was
virtio-specific.
Although the support of virtio is a primary target of this series, we
decided to generalize this work and expand it to any device [1]. So the Xen
grant mappings scheme (this property to be used for) can be theoretically
used for any device emulated by the Xen backend.
+
+description:
+ This binding indicates that Xen grant mappings scheme needs to be enabled
+ for that device and specifies the ID of Xen domain where the corresponding
+ device (backend) resides. This is needed for the option to restrict memory
+ access using Xen grant mappings to work.
+
+properties:
+ xen,dev-domid:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description:
+ The domid (domain ID) of the domain where the device (backend) is running.
+
+additionalProperties: true
+
+examples:
+ - |
+ virtio_block@3000 {
virtio@3000
ok, will change
+ compatible = "virtio,mmio";
+ reg = <0x3000 0x100>;
+ interrupts = <41>;
+
+ /* The device is located in Xen domain with ID 1 */
+ xen,dev-domid = <1>;
This fails validation:
Documentation/devicetree/bindings/arm/xen,dev-domid.example.dtb: virtio_block@3000: xen,dev-domid: [[1]] is not of type 'object'
From schema: /home/rob/proj/git/linux-dt/Documentation/devicetree/bindings/virtio/mmio.yaml
Thank you for pointing this out, my fault, I haven't "properly" checked this
before. I think, we need to remove "compatible = "virtio,mmio"; here
Uhh, no. That just means the example is incomplete. You need to add this
property or reference this schema from virtio/mmio.yaml.
ok, I got it
diff --git a/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
index 2daa8aa..d2f2140 100644
--- a/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
+++ b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
@@ -28,7 +28,7 @@ additionalProperties: true
examples:
- |
virtio_block@3000 {
- compatible = "virtio,mmio";
+ /* ... */
reg = <0x3000 0x100>;
interrupts = <41>;
The property has to be added to the virtio/mmio.yaml schema. If it is
not needed elsewhere, then *just* add the property there.
As I described above, the property is not virtio specific and can be used
for any virtualized device for which Xen grant mappings scheme needs to be
enabled (xen-grant DMA-mapping layer).
But that's a finite list of devices, right?
Right
In any case, you have to
list the property anywhere it can be used.
Agree
If I got it right, we need to add to virtio/mmio.yaml something like:
diff --git a/Documentation/devicetree/bindings/virtio/mmio.yaml
b/Documentation/devicetree/bindings/virtio/mmio.yaml
index 10c22b5..29a0932 100644
--- a/Documentation/devicetree/bindings/virtio/mmio.yaml
+++ b/Documentation/devicetree/bindings/virtio/mmio.yaml
@@ -13,6 +13,9 @@ description:
See
https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=virtio for
more details.
+allOf:
+ - $ref: /schemas/arm/xen,dev-domid.yaml#
+
properties:
compatible:
const: virtio,mmio
@@ -33,6 +36,10 @@ properties:
description: Required for devices making accesses thru an IOMMU.
maxItems: 1
+ xen,dev-domid:
+ description: Required when Xen grant mappings need to be enabled
for device.
+ $ref: /schemas/types.yaml#/definitions/uint32
+
required:
- compatible
- reg
This passed validation.
Could you please clarify, is my understanding correct?
Rob
--
Regards,
Oleksandr Tyshchenko