The stall detection mechanism allows to configure the expiration
duration and the internal counter clock frequency measured in Hz.
Add these properties in the schema.
Signed-off-by: Sebastian Ene <[email protected]>
---
.../devicetree/bindings/misc/vm-wdt.yaml | 44 +++++++++++++++++++
1 file changed, 44 insertions(+)
create mode 100644 Documentation/devicetree/bindings/misc/vm-wdt.yaml
diff --git a/Documentation/devicetree/bindings/misc/vm-wdt.yaml b/Documentation/devicetree/bindings/misc/vm-wdt.yaml
new file mode 100644
index 000000000000..cb7665a0c5af
--- /dev/null
+++ b/Documentation/devicetree/bindings/misc/vm-wdt.yaml
@@ -0,0 +1,44 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/misc/vm-wdt.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: VM watchdog
+
+description: |
+ This binding describes a CPU stall detector mechanism for virtual cpus.
+
+maintainers:
+ - Sebastian Ene <[email protected]>
+
+properties:
+ compatible:
+ enum:
+ - qemu,vm-watchdog
+ clock:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: |
+ The watchdog internal clock measure in Hz used to decrement the
+ watchdog counter register on each tick.
+ Defaults to 10 if unset.
+ timeout-sec:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: |
+ The watchdog expiration timeout measured in seconds.
+ Defaults to 8 if unset.
+
+required:
+ - compatible
+
+additionalProperties: false
+
+examples:
+ - |
+ watchdog {
+ compatible = "qemu,vm-watchdog";
+ clock = <10>;
+ timeout-sec = <8>;
+ };
+
+...
--
2.36.0.rc2.479.g8af0fa9b8e-goog
On Mon, Apr 25, 2022 at 01:42:05PM +0000, Sebastian Ene wrote:
> The stall detection mechanism allows to configure the expiration
> duration and the internal counter clock frequency measured in Hz.
> Add these properties in the schema.
>
> Signed-off-by: Sebastian Ene <[email protected]>
> ---
> .../devicetree/bindings/misc/vm-wdt.yaml | 44 +++++++++++++++++++
> 1 file changed, 44 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/misc/vm-wdt.yaml
>
> diff --git a/Documentation/devicetree/bindings/misc/vm-wdt.yaml b/Documentation/devicetree/bindings/misc/vm-wdt.yaml
> new file mode 100644
> index 000000000000..cb7665a0c5af
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/misc/vm-wdt.yaml
> @@ -0,0 +1,44 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/misc/vm-wdt.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: VM watchdog
> +
> +description: |
> + This binding describes a CPU stall detector mechanism for virtual cpus.
> +
> +maintainers:
> + - Sebastian Ene <[email protected]>
> +
> +properties:
> + compatible:
> + enum:
> + - qemu,vm-watchdog
> + clock:
'clocks' is already a defined property and 'clock' is too close. It's
also ambiguous what it is. 'clock-frequency' instead perhaps.
> + $ref: /schemas/types.yaml#/definitions/uint32
> + description: |
> + The watchdog internal clock measure in Hz used to decrement the
> + watchdog counter register on each tick.
> + Defaults to 10 if unset.
> + timeout-sec:
> + $ref: /schemas/types.yaml#/definitions/uint32
> + description: |
> + The watchdog expiration timeout measured in seconds.
> + Defaults to 8 if unset.
> +
> +required:
> + - compatible
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + watchdog {
> + compatible = "qemu,vm-watchdog";
> + clock = <10>;
> + timeout-sec = <8>;
How does one access this 'hardware'?
Why does this need to be in DT?
We have DT because h/w designers are incapable of making h/w
discoverable. Why repeat that problem with s/w interfaces?
Rob
On Mon, Apr 25, 2022 at 01:29:51PM -0500, Rob Herring wrote:
> On Mon, Apr 25, 2022 at 01:42:05PM +0000, Sebastian Ene wrote:
> > The stall detection mechanism allows to configure the expiration
> > duration and the internal counter clock frequency measured in Hz.
> > Add these properties in the schema.
> >
> > Signed-off-by: Sebastian Ene <[email protected]>
> > ---
> > .../devicetree/bindings/misc/vm-wdt.yaml | 44 +++++++++++++++++++
> > 1 file changed, 44 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/misc/vm-wdt.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/misc/vm-wdt.yaml b/Documentation/devicetree/bindings/misc/vm-wdt.yaml
> > new file mode 100644
> > index 000000000000..cb7665a0c5af
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/misc/vm-wdt.yaml
> > @@ -0,0 +1,44 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/misc/vm-wdt.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: VM watchdog
> > +
> > +description: |
> > + This binding describes a CPU stall detector mechanism for virtual cpus.
> > +
> > +maintainers:
> > + - Sebastian Ene <[email protected]>
> > +
> > +properties:
> > + compatible:
> > + enum:
> > + - qemu,vm-watchdog
> > + clock:
Hi,
>
> 'clocks' is already a defined property and 'clock' is too close. It's
> also ambiguous what it is. 'clock-frequency' instead perhaps.
>
Yes, I think 'clock-frequency' is a better name. I will update it.
> > + $ref: /schemas/types.yaml#/definitions/uint32
> > + description: |
> > + The watchdog internal clock measure in Hz used to decrement the
> > + watchdog counter register on each tick.
> > + Defaults to 10 if unset.
> > + timeout-sec:
> > + $ref: /schemas/types.yaml#/definitions/uint32
> > + description: |
> > + The watchdog expiration timeout measured in seconds.
> > + Defaults to 8 if unset.
> > +
> > +required:
> > + - compatible
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > + - |
> > + watchdog {
> > + compatible = "qemu,vm-watchdog";
> > + clock = <10>;
> > + timeout-sec = <8>;
>
> How does one access this 'hardware'?
>
This is a MMIO device.
> Why does this need to be in DT?
>
> We have DT because h/w designers are incapable of making h/w
> discoverable. Why repeat that problem with s/w interfaces?
>
We need to have this one in the DT because in a secure VM we only load
trusted DT components.
> Rob
Thanks,
Sebastian
On Thu, Apr 28, 2022 at 9:29 AM Sebastian Ene <[email protected]> wrote:
>
> On Mon, Apr 25, 2022 at 01:29:51PM -0500, Rob Herring wrote:
> > On Mon, Apr 25, 2022 at 01:42:05PM +0000, Sebastian Ene wrote:
> > > The stall detection mechanism allows to configure the expiration
> > > duration and the internal counter clock frequency measured in Hz.
> > > Add these properties in the schema.
> > >
> > > Signed-off-by: Sebastian Ene <[email protected]>
> > > ---
> > > .../devicetree/bindings/misc/vm-wdt.yaml | 44 +++++++++++++++++++
> > > 1 file changed, 44 insertions(+)
> > > create mode 100644 Documentation/devicetree/bindings/misc/vm-wdt.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/misc/vm-wdt.yaml b/Documentation/devicetree/bindings/misc/vm-wdt.yaml
> > > new file mode 100644
> > > index 000000000000..cb7665a0c5af
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/misc/vm-wdt.yaml
> > > @@ -0,0 +1,44 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/misc/vm-wdt.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: VM watchdog
> > > +
> > > +description: |
> > > + This binding describes a CPU stall detector mechanism for virtual cpus.
> > > +
> > > +maintainers:
> > > + - Sebastian Ene <[email protected]>
> > > +
> > > +properties:
> > > + compatible:
> > > + enum:
> > > + - qemu,vm-watchdog
> > > + clock:
>
> Hi,
>
> >
> > 'clocks' is already a defined property and 'clock' is too close. It's
> > also ambiguous what it is. 'clock-frequency' instead perhaps.
> >
>
> Yes, I think 'clock-frequency' is a better name. I will update it.
You are defining the register interface, so why not define a register
containing the frequency? Again, make your interface discoverable.
> > > + $ref: /schemas/types.yaml#/definitions/uint32
> > > + description: |
> > > + The watchdog internal clock measure in Hz used to decrement the
> > > + watchdog counter register on each tick.
> > > + Defaults to 10 if unset.
> > > + timeout-sec:
> > > + $ref: /schemas/types.yaml#/definitions/uint32
> > > + description: |
> > > + The watchdog expiration timeout measured in seconds.
> > > + Defaults to 8 if unset.
> > > +
> > > +required:
> > > + - compatible
> > > +
> > > +additionalProperties: false
> > > +
> > > +examples:
> > > + - |
> > > + watchdog {
> > > + compatible = "qemu,vm-watchdog";
> > > + clock = <10>;
> > > + timeout-sec = <8>;
> >
> > How does one access this 'hardware'?
> >
>
> This is a MMIO device.
Then how do you discover its address? You need 'reg'.
> > Why does this need to be in DT?
> >
> > We have DT because h/w designers are incapable of making h/w
> > discoverable. Why repeat that problem with s/w interfaces?
> >
>
> We need to have this one in the DT because in a secure VM we only load
> trusted DT components.
How does using DT make something trusted vs. any other mechanism the
hypervisor controls?
I would like to know from the virtualization folks (Xen/KVM) how they
would implement this feature? Certainly this could be reused, but then
we need an ACPI binding too for non-DT systems.
Why not use virtio?
Rob