[PATCH v7 0/3] virt: vmgenid: add devicetree bindings support

[PATCH v7 0/3] virt: vmgenid: add devicetree bindings support

[Jason A. Donenfeld]

Hi Krzysztof,

This is a cleanup of Sudan's OF vmgenid patches, simplified a bit, but
still with the same intent and mostly unchanged. I'll take this via my
random tree, but I would appreciate having your ack/review on it.

Sudan - if I've mangled something here, please let me know. I verified
this still works with ACPI in QEMU, but I don't know about your private
firecracker OF branch, so please pipe up if something is amiss. It's
basically the same thing, though, so I suspect it'll be fine.

Thanks,
Jason

Sudan Landge (3):
  virt: vmgenid: change implementation to use a platform driver
  dt-bindings: rng: Add vmgenid support
  virt: vmgenid: add support for devicetree bindings

 .../bindings/rng/microsoft,vmgenid.yaml       |  49 ++++++
 MAINTAINERS                                   |   1 +
 drivers/virt/Kconfig                          |   2 +-
 drivers/virt/vmgenid.c                        | 150 ++++++++++++++----
 4 files changed, 166 insertions(+), 36 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml

-- 
2.44.0

[PATCH v7 1/3] virt: vmgenid: change implementation to use a platform driver

[Jason A. Donenfeld]

From: Sudan Landge <sudanl@amazon.com>

Re-implement vmgenid as a platform driver in preparation for adding
devicetree bindings support in next commits.

Signed-off-by: Sudan Landge <sudanl@amazon.com>
Reviewed-by: Alexander Graf <graf@amazon.com>
[Jason: - Small style cleanups and refactoring.]
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 drivers/virt/vmgenid.c | 99 +++++++++++++++++++++++++++---------------
 1 file changed, 65 insertions(+), 34 deletions(-)

diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c
index a1c467a0e9f7..aebbd24512c9 100644
--- a/drivers/virt/vmgenid.c
+++ b/drivers/virt/vmgenid.c
@@ -7,9 +7,10 @@
  * information to random.c.
  */
 
+#include <linux/acpi.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
-#include <linux/acpi.h>
+#include <linux/platform_device.h>
 #include <linux/random.h>
 
 ACPI_MODULE_NAME("vmgenid");
@@ -21,19 +22,41 @@ struct vmgenid_state {
 	u8 this_id[VMGENID_SIZE];
 };
 
-static int vmgenid_add(struct acpi_device *device)
+static void vmgenid_notify(struct device *device)
+{
+	struct vmgenid_state *state = device->driver_data;
+	u8 old_id[VMGENID_SIZE];
+
+	memcpy(old_id, state->this_id, sizeof(old_id));
+	memcpy(state->this_id, state->next_id, sizeof(state->this_id));
+	if (!memcmp(old_id, state->this_id, sizeof(old_id)))
+		return;
+	add_vmfork_randomness(state->this_id, sizeof(state->this_id));
+}
+
+static void setup_vmgenid_state(struct vmgenid_state *state, void *virt_addr)
 {
+	state->next_id = virt_addr;
+	memcpy(state->this_id, state->next_id, sizeof(state->this_id));
+	add_device_randomness(state->this_id, sizeof(state->this_id));
+}
+
+static void vmgenid_acpi_handler(acpi_handle __always_unused handle,
+				 u32 __always_unused event, void *dev)
+{
+	vmgenid_notify(dev);
+}
+
+static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state)
+{
+	struct acpi_device *device = ACPI_COMPANION(dev);
 	struct acpi_buffer parsed = { ACPI_ALLOCATE_BUFFER };
-	struct vmgenid_state *state;
 	union acpi_object *obj;
 	phys_addr_t phys_addr;
 	acpi_status status;
+	void *virt_addr;
 	int ret = 0;
 
-	state = devm_kmalloc(&device->dev, sizeof(*state), GFP_KERNEL);
-	if (!state)
-		return -ENOMEM;
-
 	status = acpi_evaluate_object(device->handle, "ADDR", NULL, &parsed);
 	if (ACPI_FAILURE(status)) {
 		ACPI_EXCEPTION((AE_INFO, status, "Evaluating ADDR"));
@@ -49,53 +72,61 @@ static int vmgenid_add(struct acpi_device *device)
 
 	phys_addr = (obj->package.elements[0].integer.value << 0) |
 		    (obj->package.elements[1].integer.value << 32);
-	state->next_id = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB);
-	if (IS_ERR(state->next_id)) {
-		ret = PTR_ERR(state->next_id);
+
+	virt_addr = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB);
+	if (IS_ERR(virt_addr)) {
+		ret = PTR_ERR(virt_addr);
 		goto out;
 	}
+	setup_vmgenid_state(state, virt_addr);
 
-	memcpy(state->this_id, state->next_id, sizeof(state->this_id));
-	add_device_randomness(state->this_id, sizeof(state->this_id));
-
-	device->driver_data = state;
+	status = acpi_install_notify_handler(device->handle, ACPI_DEVICE_NOTIFY,
+					     vmgenid_acpi_handler, dev);
+	if (ACPI_FAILURE(status)) {
+		ret = -ENODEV;
+		goto out;
+	}
 
+	dev->driver_data = state;
 out:
 	ACPI_FREE(parsed.pointer);
 	return ret;
 }
 
-static void vmgenid_notify(struct acpi_device *device, u32 event)
+static int vmgenid_add(struct platform_device *pdev)
 {
-	struct vmgenid_state *state = acpi_driver_data(device);
-	u8 old_id[VMGENID_SIZE];
+	struct vmgenid_state *state;
+	struct device *dev = &pdev->dev;
+	int ret = 0;
 
-	memcpy(old_id, state->this_id, sizeof(old_id));
-	memcpy(state->this_id, state->next_id, sizeof(state->this_id));
-	if (!memcmp(old_id, state->this_id, sizeof(old_id)))
-		return;
-	add_vmfork_randomness(state->this_id, sizeof(state->this_id));
+	state = devm_kmalloc(dev, sizeof(*state), GFP_KERNEL);
+	if (!state)
+		return -ENOMEM;
+
+	ret = vmgenid_add_acpi(dev, state);
+
+	if (ret)
+		devm_kfree(dev, state);
+	return ret;
 }
 
-static const struct acpi_device_id vmgenid_ids[] = {
+static const struct acpi_device_id vmgenid_acpi_ids[] = {
 	{ "VMGENCTR", 0 },
 	{ "VM_GEN_COUNTER", 0 },
 	{ }
 };
-
-static struct acpi_driver vmgenid_driver = {
-	.name = "vmgenid",
-	.ids = vmgenid_ids,
-	.owner = THIS_MODULE,
-	.ops = {
-		.add = vmgenid_add,
-		.notify = vmgenid_notify
-	}
+MODULE_DEVICE_TABLE(acpi, vmgenid_acpi_ids);
+
+static struct platform_driver vmgenid_plaform_driver = {
+	.probe      = vmgenid_add,
+	.driver     = {
+		.name   = "vmgenid",
+		.acpi_match_table = vmgenid_acpi_ids,
+	},
 };
 
-module_acpi_driver(vmgenid_driver);
+module_platform_driver(vmgenid_plaform_driver)
 
-MODULE_DEVICE_TABLE(acpi, vmgenid_ids);
 MODULE_DESCRIPTION("Virtual Machine Generation ID");
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");
-- 
2.44.0

Re: [PATCH v7 1/3] virt: vmgenid: change implementation to use a platform driver

[Landge, Sudan]

On 18/04/2024 13:12, Jason A. Donenfeld wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
> 
> 
> 
> From: Sudan Landge <sudanl@amazon.com>
> 
> Re-implement vmgenid as a platform driver in preparation for adding
> devicetree bindings support in next commits.
> 
> Signed-off-by: Sudan Landge <sudanl@amazon.com>
> Reviewed-by: Alexander Graf <graf@amazon.com>
> [Jason: - Small style cleanups and refactoring.]
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
>   drivers/virt/vmgenid.c | 99 +++++++++++++++++++++++++++---------------
>   1 file changed, 65 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c
> index a1c467a0e9f7..aebbd24512c9 100644
> --- a/drivers/virt/vmgenid.c
> +++ b/drivers/virt/vmgenid.c
> @@ -7,9 +7,10 @@
>    * information to random.c.
>    */
> 
> +#include <linux/acpi.h>
>   #include <linux/kernel.h>
>   #include <linux/module.h>
> -#include <linux/acpi.h>
> +#include <linux/platform_device.h>
>   #include <linux/random.h>
> 
>   ACPI_MODULE_NAME("vmgenid");
> @@ -21,19 +22,41 @@ struct vmgenid_state {
>          u8 this_id[VMGENID_SIZE];
>   };
> 
> -static int vmgenid_add(struct acpi_device *device)
> +static void vmgenid_notify(struct device *device)
> +{
> +       struct vmgenid_state *state = device->driver_data;
> +       u8 old_id[VMGENID_SIZE];
> +
> +       memcpy(old_id, state->this_id, sizeof(old_id));
> +       memcpy(state->this_id, state->next_id, sizeof(state->this_id));
> +       if (!memcmp(old_id, state->this_id, sizeof(old_id)))
> +               return;
> +       add_vmfork_randomness(state->this_id, sizeof(state->this_id));
> +}
> +
> +static void setup_vmgenid_state(struct vmgenid_state *state, void *virt_addr)
>   {
> +       state->next_id = virt_addr;
> +       memcpy(state->this_id, state->next_id, sizeof(state->this_id));
> +       add_device_randomness(state->this_id, sizeof(state->this_id));
> +}
> +
> +static void vmgenid_acpi_handler(acpi_handle __always_unused handle,
> +                                u32 __always_unused event, void *dev)
> +{
> +       vmgenid_notify(dev);
> +}
> +
> +static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state)
> +{
> +       struct acpi_device *device = ACPI_COMPANION(dev);
>          struct acpi_buffer parsed = { ACPI_ALLOCATE_BUFFER };
> -       struct vmgenid_state *state;
>          union acpi_object *obj;
>          phys_addr_t phys_addr;
>          acpi_status status;
> +       void *virt_addr;
>          int ret = 0;
> 
> -       state = devm_kmalloc(&device->dev, sizeof(*state), GFP_KERNEL);
> -       if (!state)
> -               return -ENOMEM;
> -
>          status = acpi_evaluate_object(device->handle, "ADDR", NULL, &parsed);
>          if (ACPI_FAILURE(status)) {
>                  ACPI_EXCEPTION((AE_INFO, status, "Evaluating ADDR"));
> @@ -49,53 +72,61 @@ static int vmgenid_add(struct acpi_device *device)
> 
>          phys_addr = (obj->package.elements[0].integer.value << 0) |
>                      (obj->package.elements[1].integer.value << 32);
> -       state->next_id = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB);
> -       if (IS_ERR(state->next_id)) {
> -               ret = PTR_ERR(state->next_id);
> +
> +       virt_addr = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB);
> +       if (IS_ERR(virt_addr)) {
> +               ret = PTR_ERR(virt_addr);
>                  goto out;
>          }
> +       setup_vmgenid_state(state, virt_addr);
> 
> -       memcpy(state->this_id, state->next_id, sizeof(state->this_id));
> -       add_device_randomness(state->this_id, sizeof(state->this_id));
> -
> -       device->driver_data = state;
> +       status = acpi_install_notify_handler(device->handle, ACPI_DEVICE_NOTIFY,
> +                                            vmgenid_acpi_handler, dev);
> +       if (ACPI_FAILURE(status)) {
> +               ret = -ENODEV;
> +               goto out;
> +       }
> 
> +       dev->driver_data = state;
>   out:
>          ACPI_FREE(parsed.pointer);
>          return ret;
>   }
> 
> -static void vmgenid_notify(struct acpi_device *device, u32 event)
> +static int vmgenid_add(struct platform_device *pdev)
>   {
> -       struct vmgenid_state *state = acpi_driver_data(device);
> -       u8 old_id[VMGENID_SIZE];
> +       struct vmgenid_state *state;
> +       struct device *dev = &pdev->dev;
> +       int ret = 0;
> 
> -       memcpy(old_id, state->this_id, sizeof(old_id));
> -       memcpy(state->this_id, state->next_id, sizeof(state->this_id));
> -       if (!memcmp(old_id, state->this_id, sizeof(old_id)))
> -               return;
> -       add_vmfork_randomness(state->this_id, sizeof(state->this_id));
> +       state = devm_kmalloc(dev, sizeof(*state), GFP_KERNEL);
> +       if (!state)
> +               return -ENOMEM;
> +
> +       ret = vmgenid_add_acpi(dev, state);
> +
> +       if (ret)
> +               devm_kfree(dev, state);
> +       return ret;
>   }
> 
> -static const struct acpi_device_id vmgenid_ids[] = {
> +static const struct acpi_device_id vmgenid_acpi_ids[] = {
>          { "VMGENCTR", 0 },
>          { "VM_GEN_COUNTER", 0 },
>          { }
>   };
> -
> -static struct acpi_driver vmgenid_driver = {
> -       .name = "vmgenid",
> -       .ids = vmgenid_ids,
> -       .owner = THIS_MODULE,
> -       .ops = {
> -               .add = vmgenid_add,
> -               .notify = vmgenid_notify
> -       }
> +MODULE_DEVICE_TABLE(acpi, vmgenid_acpi_ids);
> +
> +static struct platform_driver vmgenid_plaform_driver = {
> +       .probe      = vmgenid_add,
> +       .driver     = {
> +               .name   = "vmgenid",
> +               .acpi_match_table = vmgenid_acpi_ids,
> +       },
>   };
> 
> -module_acpi_driver(vmgenid_driver);
> +module_platform_driver(vmgenid_plaform_driver)
> 
> -MODULE_DEVICE_TABLE(acpi, vmgenid_ids);
>   MODULE_DESCRIPTION("Virtual Machine Generation ID");
>   MODULE_LICENSE("GPL v2");
>   MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");
> --
> 2.44.0
> 
Since I am on leave, looping in Babis to review/verify the patches.

[PATCH v7 2/3] dt-bindings: rng: Add vmgenid support

[Jason A. Donenfeld]

From: Sudan Landge <sudanl@amazon.com>

Virtual Machine Generation ID driver was introduced in commit
af6b54e2b5ba ("virt: vmgenid: notify RNG of VM fork and supply
generation ID"), as an ACPI only device.

VMGenID specification http://go.microsoft.com/fwlink/?LinkId=260709
defines a mechanism for the BIOS/hypervisors to communicate to the
virtual machine that it is executed with a different configuration (e.g.
snapshot execution or creation from a template).  The guest operating
system can use the notification for various purposes such as
re-initializing its random number generator etc.

As per the specs, hypervisor should provide a globally unique
identified, or GUID via ACPI.

This patch tries to mimic the mechanism to provide the same
functionality which is for a hypervisor/BIOS to notify the virtual
machine when it is executed with a different configuration.

As part of this support the devicetree bindings requires the hypervisors
or BIOS to provide a memory address which holds the GUID and an IRQ
which is used to notify when there is a change in the GUID.  The memory
exposed in the DT should follow the rules defined in the vmgenid spec
mentioned above.

Reason for this change: Chosing ACPI or devicetree is an intrinsic part
of an hypervisor design.  Without going into details of why a hypervisor
would chose DT over ACPI, we would like to highlight that the
hypervisors that have chose devicetree and now want to make use of the
vmgenid functionality cannot do so today because vmgenid is an ACPI only
device.  This forces these hypervisors to change their design which
could have undesirable impacts on their use-cases, test-scenarios etc.

The point of vmgenid is to provide a mechanism to discover a GUID when
the execution state of a virtual machine changes and the simplest way to
do it is pass a memory location and an interrupt via devicetree.  It
would complicate things unnecessarily if instead of using devicetree, we
try to implement a new protocol or modify other protocols to somehow
provide the same functionility.

We believe that adding a devicetree binding for vmgenid is a simpler,
better alternative to provide the same functionality and will allow such
hypervisors as mentioned above to continue using devicetree.

More references to the vmgenid specs are found below.

Signed-off-by: Sudan Landge <sudanl@amazon.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Alexander Graf <graf@amazon.com>
Link: https://www.qemu.org/docs/master/specs/vmgenid.html
Link: https://learn.microsoft.com/en-us/windows/win32/hyperv_v2/virtual-machine-generation-identifier
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 .../bindings/rng/microsoft,vmgenid.yaml       | 49 +++++++++++++++++++
 MAINTAINERS                                   |  1 +
 2 files changed, 50 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml

diff --git a/Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml b/Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml
new file mode 100644
index 000000000000..8f20dee93e7e
--- /dev/null
+++ b/Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml
@@ -0,0 +1,49 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rng/microsoft,vmgenid.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Virtual Machine Generation ID
+
+maintainers:
+  - Jason A. Donenfeld <Jason@zx2c4.com>
+
+description:
+  Firmwares or hypervisors can use this devicetree to describe an
+  interrupt and a shared resource to inject a Virtual Machine Generation ID.
+  Virtual Machine Generation ID is a globally unique identifier (GUID) and
+  the devicetree binding follows VMGenID specification defined in
+  http://go.microsoft.com/fwlink/?LinkId=260709.
+
+properties:
+  compatible:
+    const: microsoft,vmgenid
+
+  reg:
+    description:
+      Specifies a 16-byte VMGenID in endianness-agnostic hexadecimal format.
+    maxItems: 1
+
+  interrupts:
+    description:
+      Interrupt used to notify that a new VMGenID is available.
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    rng@80000000 {
+      compatible = "microsoft,vmgenid";
+      reg = <0x80000000 0x1000>;
+      interrupts = <GIC_SPI 35 IRQ_TYPE_EDGE_RISING>;
+    };
+
+...
diff --git a/MAINTAINERS b/MAINTAINERS
index aa3b947fb080..c84ac9258a48 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18463,6 +18463,7 @@ M:	"Theodore Ts'o" <tytso@mit.edu>
 M:	Jason A. Donenfeld <Jason@zx2c4.com>
 S:	Maintained
 T:	git https://git.kernel.org/pub/scm/linux/kernel/git/crng/random.git
+F:	Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml
 F:	drivers/char/random.c
 F:	drivers/virt/vmgenid.c
 
-- 
2.44.0

Re: [PATCH v7 2/3] dt-bindings: rng: Add vmgenid support

[Landge, Sudan]

On 18/04/2024 13:12, Jason A. Donenfeld wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
> 
> 
> 
> From: Sudan Landge <sudanl@amazon.com>
> 
> Virtual Machine Generation ID driver was introduced in commit
> af6b54e2b5ba ("virt: vmgenid: notify RNG of VM fork and supply
> generation ID"), as an ACPI only device.
> 
> VMGenID specification http://go.microsoft.com/fwlink/?LinkId=260709
> defines a mechanism for the BIOS/hypervisors to communicate to the
> virtual machine that it is executed with a different configuration (e.g.
> snapshot execution or creation from a template).  The guest operating
> system can use the notification for various purposes such as
> re-initializing its random number generator etc.
> 
> As per the specs, hypervisor should provide a globally unique
> identified, or GUID via ACPI.
> 
> This patch tries to mimic the mechanism to provide the same
> functionality which is for a hypervisor/BIOS to notify the virtual
> machine when it is executed with a different configuration.
> 
> As part of this support the devicetree bindings requires the hypervisors
> or BIOS to provide a memory address which holds the GUID and an IRQ
> which is used to notify when there is a change in the GUID.  The memory
> exposed in the DT should follow the rules defined in the vmgenid spec
> mentioned above.
> 
> Reason for this change: Chosing ACPI or devicetree is an intrinsic part
> of an hypervisor design.  Without going into details of why a hypervisor
> would chose DT over ACPI, we would like to highlight that the
> hypervisors that have chose devicetree and now want to make use of the
> vmgenid functionality cannot do so today because vmgenid is an ACPI only
> device.  This forces these hypervisors to change their design which
> could have undesirable impacts on their use-cases, test-scenarios etc.
> 
> The point of vmgenid is to provide a mechanism to discover a GUID when
> the execution state of a virtual machine changes and the simplest way to
> do it is pass a memory location and an interrupt via devicetree.  It
> would complicate things unnecessarily if instead of using devicetree, we
> try to implement a new protocol or modify other protocols to somehow
> provide the same functionility.
> 
> We believe that adding a devicetree binding for vmgenid is a simpler,
> better alternative to provide the same functionality and will allow such
> hypervisors as mentioned above to continue using devicetree.
> 
> More references to the vmgenid specs are found below.
> 
> Signed-off-by: Sudan Landge <sudanl@amazon.com>
> Reviewed-by: Rob Herring <robh@kernel.org>
> Reviewed-by: Alexander Graf <graf@amazon.com>
> Link: https://www.qemu.org/docs/master/specs/vmgenid.html
> Link: https://learn.microsoft.com/en-us/windows/win32/hyperv_v2/virtual-machine-generation-identifier
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
>   .../bindings/rng/microsoft,vmgenid.yaml       | 49 +++++++++++++++++++
>   MAINTAINERS                                   |  1 +
>   2 files changed, 50 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml
> 
> diff --git a/Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml b/Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml
> new file mode 100644
> index 000000000000..8f20dee93e7e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml
> @@ -0,0 +1,49 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/rng/microsoft,vmgenid.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Virtual Machine Generation ID
> +
> +maintainers:
> +  - Jason A. Donenfeld <Jason@zx2c4.com>
> +
> +description:
> +  Firmwares or hypervisors can use this devicetree to describe an
> +  interrupt and a shared resource to inject a Virtual Machine Generation ID.
> +  Virtual Machine Generation ID is a globally unique identifier (GUID) and
> +  the devicetree binding follows VMGenID specification defined in
> +  http://go.microsoft.com/fwlink/?LinkId=260709.
> +
> +properties:
> +  compatible:
> +    const: microsoft,vmgenid
> +
> +  reg:
> +    description:
> +      Specifies a 16-byte VMGenID in endianness-agnostic hexadecimal format.
> +    maxItems: 1
> +
> +  interrupts:
> +    description:
> +      Interrupt used to notify that a new VMGenID is available.
> +    maxItems: 1
> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +    rng@80000000 {
> +      compatible = "microsoft,vmgenid";
> +      reg = <0x80000000 0x1000>;
> +      interrupts = <GIC_SPI 35 IRQ_TYPE_EDGE_RISING>;
> +    };
> +
> +...
> diff --git a/MAINTAINERS b/MAINTAINERS
> index aa3b947fb080..c84ac9258a48 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -18463,6 +18463,7 @@ M:      "Theodore Ts'o" <tytso@mit.edu>
>   M:     Jason A. Donenfeld <Jason@zx2c4.com>
>   S:     Maintained
>   T:     git https://git.kernel.org/pub/scm/linux/kernel/git/crng/random.git
> +F:     Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml
>   F:     drivers/char/random.c
>   F:     drivers/virt/vmgenid.c
> 
> --
> 2.44.0
> 
Since I am on leave, looping in Babis to review/verify the patches.

Re: [PATCH v7 2/3] dt-bindings: rng: Add vmgenid support

[Krzysztof Kozlowski]

On 19/04/2024 15:31, Landge, Sudan wrote:
>> +...
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index aa3b947fb080..c84ac9258a48 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -18463,6 +18463,7 @@ M:      "Theodore Ts'o" <tytso@mit.edu>
>>   M:     Jason A. Donenfeld <Jason@zx2c4.com>
>>   S:     Maintained
>>   T:     git https://git.kernel.org/pub/scm/linux/kernel/git/crng/random.git
>> +F:     Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml
>>   F:     drivers/char/random.c
>>   F:     drivers/virt/vmgenid.c
>>
>> --
>> 2.44.0
>>
> Since I am on leave, looping in Babis to review/verify the patches.

You can bounce emails to Babis. Or ask him to use lei/lore. No need to
Cc all of us with such forward. This is just unnecessary noise in our
mailboxes.

Especially if you want to get some reviews...

Best regards,
Krzysztof

[PATCH v7 3/3] virt: vmgenid: add support for devicetree bindings

[Jason A. Donenfeld]

From: Sudan Landge <sudanl@amazon.com>

Extend the vmgenid platform driver to support devicetree bindings. With
this support, hypervisors can send vmgenid notifications to the virtual
machine without the need to enable ACPI. The bindings are located at:
Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml

Since this makes the driver work for both ACPI and devicetree, adjust
the Kconfig to include `|| OF`, which in turn means accounting for
!CONFIG_ACPI in the code with a short ifdef.

Signed-off-by: Sudan Landge <sudanl@amazon.com>
Reviewed-by: Alexander Graf <graf@amazon.com>
[Jason: - Small style cleanups and refactoring.
        - Fold in Kconfig OF dependency and ACPI conditionalization. ]
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 drivers/virt/Kconfig   |  2 +-
 drivers/virt/vmgenid.c | 53 ++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
index 40129b6f0eca..017d6c38c3ba 100644
--- a/drivers/virt/Kconfig
+++ b/drivers/virt/Kconfig
@@ -16,7 +16,7 @@ if VIRT_DRIVERS
 config VMGENID
 	tristate "Virtual Machine Generation ID driver"
 	default y
-	depends on ACPI
+	depends on ACPI || OF
 	help
 	  Say Y here to use the hypervisor-provided Virtual Machine Generation ID
 	  to reseed the RNG when the VM is cloned. This is highly recommended if
diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c
index aebbd24512c9..7f2d1e5656df 100644
--- a/drivers/virt/vmgenid.c
+++ b/drivers/virt/vmgenid.c
@@ -2,12 +2,13 @@
 /*
  * Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
  *
- * The "Virtual Machine Generation ID" is exposed via ACPI and changes when a
+ * The "Virtual Machine Generation ID" is exposed via ACPI or DT and changes when a
  * virtual machine forks or is cloned. This driver exists for shepherding that
  * information to random.c.
  */
 
 #include <linux/acpi.h>
+#include <linux/interrupt.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
@@ -41,6 +42,7 @@ static void setup_vmgenid_state(struct vmgenid_state *state, void *virt_addr)
 	add_device_randomness(state->this_id, sizeof(state->this_id));
 }
 
+#ifdef CONFIG_ACPI
 static void vmgenid_acpi_handler(acpi_handle __always_unused handle,
 				 u32 __always_unused event, void *dev)
 {
@@ -92,6 +94,43 @@ static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state)
 	ACPI_FREE(parsed.pointer);
 	return ret;
 }
+#else
+static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state)
+{
+	return -EINVAL;
+}
+#endif
+
+static irqreturn_t vmgenid_of_irq_handler(int __always_unused irq, void *dev)
+{
+	vmgenid_notify(dev);
+	return IRQ_HANDLED;
+}
+
+static int vmgenid_add_of(struct platform_device *pdev,
+			  struct vmgenid_state *state)
+{
+	void *virt_addr;
+	int ret;
+
+	virt_addr = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (IS_ERR(virt_addr))
+		return PTR_ERR(virt_addr);
+
+	setup_vmgenid_state(state, virt_addr);
+
+	ret = platform_get_irq(pdev, 0);
+	if (ret)
+		return ret;
+
+	ret = devm_request_irq(&pdev->dev, ret, vmgenid_of_irq_handler,
+			       IRQF_SHARED, "vmgenid", &pdev->dev);
+	if (ret)
+		return ret;
+
+	pdev->dev.driver_data = state;
+	return 0;
+}
 
 static int vmgenid_add(struct platform_device *pdev)
 {
@@ -103,13 +142,22 @@ static int vmgenid_add(struct platform_device *pdev)
 	if (!state)
 		return -ENOMEM;
 
-	ret = vmgenid_add_acpi(dev, state);
+	if (dev->of_node)
+		ret = vmgenid_add_of(pdev, state);
+	else
+		ret = vmgenid_add_acpi(dev, state);
 
 	if (ret)
 		devm_kfree(dev, state);
 	return ret;
 }
 
+static const struct of_device_id vmgenid_of_ids[] = {
+	{ .compatible = "microsoft,vmgenid", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, vmgenid_of_ids);
+
 static const struct acpi_device_id vmgenid_acpi_ids[] = {
 	{ "VMGENCTR", 0 },
 	{ "VM_GEN_COUNTER", 0 },
@@ -122,6 +170,7 @@ static struct platform_driver vmgenid_plaform_driver = {
 	.driver     = {
 		.name   = "vmgenid",
 		.acpi_match_table = vmgenid_acpi_ids,
+		.of_match_table = vmgenid_of_ids,
 	},
 };
 
-- 
2.44.0

Re: [PATCH v7 3/3] virt: vmgenid: add support for devicetree bindings

[Landge, Sudan]

On 18/04/2024 13:12, Jason A. Donenfeld wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
> 
> 
> 
> From: Sudan Landge <sudanl@amazon.com>
> 
> Extend the vmgenid platform driver to support devicetree bindings. With
> this support, hypervisors can send vmgenid notifications to the virtual
> machine without the need to enable ACPI. The bindings are located at:
> Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml
> 
> Since this makes the driver work for both ACPI and devicetree, adjust
> the Kconfig to include `|| OF`, which in turn means accounting for
> !CONFIG_ACPI in the code with a short ifdef.
> 
> Signed-off-by: Sudan Landge <sudanl@amazon.com>
> Reviewed-by: Alexander Graf <graf@amazon.com>
> [Jason: - Small style cleanups and refactoring.
>          - Fold in Kconfig OF dependency and ACPI conditionalization. ]
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
>   drivers/virt/Kconfig   |  2 +-
>   drivers/virt/vmgenid.c | 53 ++++++++++++++++++++++++++++++++++++++++--
>   2 files changed, 52 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
> index 40129b6f0eca..017d6c38c3ba 100644
> --- a/drivers/virt/Kconfig
> +++ b/drivers/virt/Kconfig
> @@ -16,7 +16,7 @@ if VIRT_DRIVERS
>   config VMGENID
>          tristate "Virtual Machine Generation ID driver"
>          default y
> -       depends on ACPI
> +       depends on ACPI || OF

Version 2 of the patches had these flag but were removed in version3 
following the below review comment from Rob:
"One of those is pretty much always enabled, so it can probably be dropped."
reference : 
https://lore.kernel.org/lkml/CAL_JsqJoB5CYajWuntMdQrJZir+ZA-69Q0cwvxcVZAqs-mXC+Q@mail.gmail.com/


>          help
>            Say Y here to use the hypervisor-provided Virtual Machine Generation ID
>            to reseed the RNG when the VM is cloned. This is highly recommended if
> diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c
> index aebbd24512c9..7f2d1e5656df 100644
> --- a/drivers/virt/vmgenid.c
> +++ b/drivers/virt/vmgenid.c
> @@ -2,12 +2,13 @@
>   /*
>    * Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
>    *
> - * The "Virtual Machine Generation ID" is exposed via ACPI and changes when a
> + * The "Virtual Machine Generation ID" is exposed via ACPI or DT and changes when a
>    * virtual machine forks or is cloned. This driver exists for shepherding that
>    * information to random.c.
>    */
> 
>   #include <linux/acpi.h>
> +#include <linux/interrupt.h>
>   #include <linux/kernel.h>
>   #include <linux/module.h>
>   #include <linux/platform_device.h>
> @@ -41,6 +42,7 @@ static void setup_vmgenid_state(struct vmgenid_state *state, void *virt_addr)
>          add_device_randomness(state->this_id, sizeof(state->this_id));
>   }
> 
> +#ifdef CONFIG_ACPI
>   static void vmgenid_acpi_handler(acpi_handle __always_unused handle,
>                                   u32 __always_unused event, void *dev)
>   {
> @@ -92,6 +94,43 @@ static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state)
>          ACPI_FREE(parsed.pointer);
>          return ret;
>   }
> +#else
> +static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state)
> +{
> +       return -EINVAL;
> +}
> +#endif
> +
> +static irqreturn_t vmgenid_of_irq_handler(int __always_unused irq, void *dev)
> +{
> +       vmgenid_notify(dev);
> +       return IRQ_HANDLED;
> +}
> +
> +static int vmgenid_add_of(struct platform_device *pdev,
> +                         struct vmgenid_state *state)
> +{
> +       void *virt_addr;
> +       int ret;
> +
> +       virt_addr = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
> +       if (IS_ERR(virt_addr))
> +               return PTR_ERR(virt_addr);
> +
> +       setup_vmgenid_state(state, virt_addr);
> +
> +       ret = platform_get_irq(pdev, 0);
> +       if (ret)
> +               return ret;
> +
> +       ret = devm_request_irq(&pdev->dev, ret, vmgenid_of_irq_handler,
> +                              IRQF_SHARED, "vmgenid", &pdev->dev);
> +       if (ret)
> +               return ret;
> +
> +       pdev->dev.driver_data = state;
> +       return 0;
> +}
> 
>   static int vmgenid_add(struct platform_device *pdev)
>   {
> @@ -103,13 +142,22 @@ static int vmgenid_add(struct platform_device *pdev)
>          if (!state)
>                  return -ENOMEM;
> 
> -       ret = vmgenid_add_acpi(dev, state);
> +       if (dev->of_node)
> +               ret = vmgenid_add_of(pdev, state);
> +       else
> +               ret = vmgenid_add_acpi(dev, state);
> 
>          if (ret)
>                  devm_kfree(dev, state);
>          return ret;
>   }
> 
> +static const struct of_device_id vmgenid_of_ids[] = {
> +       { .compatible = "microsoft,vmgenid", },
> +       { },
> +};
> +MODULE_DEVICE_TABLE(of, vmgenid_of_ids);
> +
>   static const struct acpi_device_id vmgenid_acpi_ids[] = {
>          { "VMGENCTR", 0 },
>          { "VM_GEN_COUNTER", 0 },
> @@ -122,6 +170,7 @@ static struct platform_driver vmgenid_plaform_driver = {
>          .driver     = {
>                  .name   = "vmgenid",
>                  .acpi_match_table = vmgenid_acpi_ids,
> +               .of_match_table = vmgenid_of_ids,
>          },
>   };
> 
> --
> 2.44.0
> 
Since I am on leave, looping in Babis to review/verify the patches.

Re: [PATCH v7 3/3] virt: vmgenid: add support for devicetree bindings

[Jason A. Donenfeld]

Hi Rob,

On Fri, Apr 19, 2024 at 3:30 PM Landge, Sudan <sudanl@amazon.co.uk> wrote:
> >   config VMGENID
> >          tristate "Virtual Machine Generation ID driver"
> >          default y
> > -       depends on ACPI
> > +       depends on ACPI || OF
>
> Version 2 of the patches had these flag but were removed in version3
> following the below review comment from Rob:
> "One of those is pretty much always enabled, so it can probably be dropped."
> reference :
> https://lore.kernel.org/lkml/CAL_JsqJoB5CYajWuntMdQrJZir+ZA-69Q0cwvxcVZAqs-mXC+Q@mail.gmail.com/

Are you sure about that? I see other drivers that depend on `ACPI ||
OF`, and this driver is totally useless without either disabled
(right?), so the dependency makes sense. I think? Not an expert in
this area, so I'm happy to defer to what you know is best, but I did
want to lightly pushback a bit.

Jason

Re: [PATCH v7 3/3] virt: vmgenid: add support for devicetree bindings

[Krzysztof Kozlowski]

On 19/04/2024 16:02, Jason A. Donenfeld wrote:
> Hi Rob,
> 
> On Fri, Apr 19, 2024 at 3:30 PM Landge, Sudan <sudanl@amazon.co.uk> wrote:
>>>   config VMGENID
>>>          tristate "Virtual Machine Generation ID driver"
>>>          default y
>>> -       depends on ACPI
>>> +       depends on ACPI || OF
>>
>> Version 2 of the patches had these flag but were removed in version3
>> following the below review comment from Rob:
>> "One of those is pretty much always enabled, so it can probably be dropped."
>> reference :
>> https://lore.kernel.org/lkml/CAL_JsqJoB5CYajWuntMdQrJZir+ZA-69Q0cwvxcVZAqs-mXC+Q@mail.gmail.com/
> 
> Are you sure about that? I see other drivers that depend on `ACPI ||
> OF`, and this driver is totally useless without either disabled
> (right?), so the dependency makes sense. I think? Not an expert in
> this area, so I'm happy to defer to what you know is best, but I did
> want to lightly pushback a bit.
> 

There are just 18 cases, so I would argue that it's not a real pattern
but could be just growing organically, without really thinking.

The driver could still be probed on some !ACPI and !OF system via driver
name matching.

Keeping it as is seems harmless, but OTOH, if this stays, you miss ||
COMPILE_TEST

Best regards,
Krzysztof

Re: [PATCH v7 3/3] virt: vmgenid: add support for devicetree bindings

[Jason A. Donenfeld]

On Fri, Apr 19, 2024 at 4:14 PM Krzysztof Kozlowski
<krzysztof.kozlowski@linaro.org> wrote:
>
> On 19/04/2024 16:02, Jason A. Donenfeld wrote:
> > Hi Rob,
> >
> > On Fri, Apr 19, 2024 at 3:30 PM Landge, Sudan <sudanl@amazon.co.uk> wrote:
> >>>   config VMGENID
> >>>          tristate "Virtual Machine Generation ID driver"
> >>>          default y
> >>> -       depends on ACPI
> >>> +       depends on ACPI || OF
> >>
> >> Version 2 of the patches had these flag but were removed in version3
> >> following the below review comment from Rob:
> >> "One of those is pretty much always enabled, so it can probably be dropped."
> >> reference :
> >> https://lore.kernel.org/lkml/CAL_JsqJoB5CYajWuntMdQrJZir+ZA-69Q0cwvxcVZAqs-mXC+Q@mail.gmail.com/
> >
> > Are you sure about that? I see other drivers that depend on `ACPI ||
> > OF`, and this driver is totally useless without either disabled
> > (right?), so the dependency makes sense. I think? Not an expert in
> > this area, so I'm happy to defer to what you know is best, but I did
> > want to lightly pushback a bit.
> >
>
> There are just 18 cases, so I would argue that it's not a real pattern
> but could be just growing organically, without really thinking.
>
> The driver could still be probed on some !ACPI and !OF system via driver
> name matching.
>
> Keeping it as is seems harmless, but OTOH, if this stays, you miss ||
> COMPILE_TEST

Fair enough, I'll ditch it.

Jason

Re: [PATCH v7 0/3] virt: vmgenid: add devicetree bindings support

[Landge, Sudan]

On 18/04/2024 13:12, Jason A. Donenfeld wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
> 
> 
> 
> Hi Krzysztof,
> 
> This is a cleanup of Sudan's OF vmgenid patches, simplified a bit, but
> still with the same intent and mostly unchanged. I'll take this via my
> random tree, but I would appreciate having your ack/review on it.
> 
> Sudan - if I've mangled something here, please let me know. I verified
> this still works with ACPI in QEMU, but I don't know about your private
> firecracker OF branch, so please pipe up if something is amiss. It's
> basically the same thing, though, so I suspect it'll be fine.
> 
> Thanks,
> Jason
> 
> Sudan Landge (3):
>    virt: vmgenid: change implementation to use a platform driver
>    dt-bindings: rng: Add vmgenid support
>    virt: vmgenid: add support for devicetree bindings
> 
>   .../bindings/rng/microsoft,vmgenid.yaml       |  49 ++++++
>   MAINTAINERS                                   |   1 +
>   drivers/virt/Kconfig                          |   2 +-
>   drivers/virt/vmgenid.c                        | 150 ++++++++++++++----
>   4 files changed, 166 insertions(+), 36 deletions(-)
>   create mode 100644 Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml
> 
> --
> 2.44.0
> 
Hi Jason,

Thank you very much for helping us with the patches. I am on a personal 
leave with very limited access to mails/system so Babis is helping me by 
taking over the task. Looping in Babis so that he can verify the patch 
with DT. I would also kindly request you to please loop in Babis 
(bchalios@amazon.es) for future discussion on these patches.

Thanks and regards,
Sudan