Messages in this thread Patch in this message | | | Subject | Re: [PATCH V1 4/6] dt-bindings: Add xen,dev-domid property description for xen-grant DMA ops | From | Oleksandr <> | Date | Thu, 5 May 2022 13:12:17 +0300 |
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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@epam.com> >>>> >>>> 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@epam.com> >>>> --- >>>> 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@epam.com> >>>> + >>>> +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
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