Re: [PATCH v1 4/4] virt: vmgenid: add support for devicetree bindings

[Krzysztof Kozlowski]

On 19/03/2024 15:32, Sudan Landge wrote:
> 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/vmgenid/vmgenid.yaml
> 
> Signed-off-by: Sudan Landge <sudanl@xxxxxxxxxx>
> ---
>  drivers/virt/Kconfig   |  2 +-
>  drivers/virt/vmgenid.c | 90 +++++++++++++++++++++++++++++++++++++++---
>  2 files changed, 86 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
> index 40129b6f0eca..4f33ee2f0372 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 e82b344a9d61..96a3ff8ec05a 100644
> --- a/drivers/virt/vmgenid.c
> +++ b/drivers/virt/vmgenid.c
> @@ -2,7 +2,7 @@
>  /*
>   * Copyright (C) 2022 Jason A. Donenfeld <Jason@xxxxxxxxx>. 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.
>   */
> @@ -12,6 +12,12 @@
>  #include <linux/acpi.h>
>  #include <linux/random.h>
>  #include <acpi/actypes.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/of_address.h>
> +#include <linux/of_device.h>
> +#include <linux/of_irq.h>
>  #include <linux/platform_device.h>
>  
>  ACPI_MODULE_NAME("vmgenid");
> @@ -21,6 +27,7 @@ enum { VMGENID_SIZE = 16 };
>  struct vmgenid_state {
>  	u8 *next_id;
>  	u8 this_id[VMGENID_SIZE];
> +	unsigned int irq;
>  };
>  
>  static void vmgenid_notify(struct device *device)
> @@ -42,6 +49,13 @@ static void vmgenid_acpi_handler(acpi_handle handle, u32 event, void *dev)
>  	vmgenid_notify(dev);
>  }
>  
> +static irqreturn_t vmgenid_of_irq_handler(int irq, void *dev)
> +{
> +	vmgenid_notify(dev);
> +
> +	return IRQ_HANDLED;
> +}
> +
>  static int setup_vmgenid_state(struct vmgenid_state *state, u8 *next_id)
>  {
>  	if (IS_ERR(next_id))
> @@ -98,6 +112,43 @@ static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state)
>  	return ret;
>  }
>  
> +static int vmgenid_add_of(struct device *dev, struct vmgenid_state *state)
> +{
> +	struct resource res;
> +	int ret = 0;
> +
> +	if (of_address_to_resource(dev->of_node, 0, &res)) {
> +		dev_err(dev, "Failed to get resources from device tree");
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	if (!__request_mem_region(res.start, resource_size(&res),
> +				  "vmgenid", IORESOURCE_EXCLUSIVE)) {
> +		dev_err(dev, "Failed to request mem region");
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	ret = setup_vmgenid_state(state, of_iomap(dev->of_node, 0));
> +	if (ret)
> +		goto out;
> +
> +	state->irq = irq_of_parse_and_map(dev->of_node, 0);
> +	dev->driver_data = state;
> +
> +	if (request_irq(state->irq, vmgenid_of_irq_handler,
> +			IRQF_SHARED, "vmgenid", dev) < 0) {
> +		dev_err(dev, "request_irq failed");
> +		dev->driver_data = NULL;
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +out:
> +	return ret;
> +}
> +
>  static int vmgenid_add(struct platform_device *pdev)
>  {
>  	struct vmgenid_state *state;
> @@ -108,7 +159,10 @@ 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(dev, state);
> +	else
> +		ret = vmgenid_add_acpi(dev, state);
>  
>  	if (ret)
>  		devm_kfree(dev, state);
> @@ -116,7 +170,30 @@ static int vmgenid_add(struct platform_device *pdev)
>  	return ret;
>  }
>  
> -static const struct acpi_device_id vmgenid_ids[] = {
> +static int vmgenid_remove(struct platform_device *pdev)
> +{
> +	struct vmgenid_state *state = NULL;
> +

How is this related to the patch? Removal is valid (or invalid)
regardless your bind method.

> +	if (!pdev)
> +		return -EINVAL;
> +
> +	state = pdev->dev.driver_data;
> +
> +	if (state && pdev->dev.of_node)
> +		free_irq(state->irq, &pdev->dev);
> +
> +	if (state)
> +		devm_kfree(&pdev->dev, state);

Why do you free devm memory? Which driver callback allocated it?

> +
> +	return 0;
> +}
> +
> +static const struct of_device_id vmgenid_of_ids[] = {
> +	{ .compatible = "linux,vmgenctr", },
> +	{},
> +};
> +
> +static const struct acpi_device_id vmgenid_acpi_ids[] = {
>  	{ "VMGENCTR", 0 },
>  	{ "VM_GEN_COUNTER", 0 },
>  	{ }
> @@ -124,9 +201,11 @@ static const struct acpi_device_id vmgenid_ids[] = {
>  
>  static struct platform_driver vmgenid_plaform_driver = {
>  	.probe      = vmgenid_add,
> +	.remove     = vmgenid_remove,
>  	.driver     = {
>  		.name   = "vmgenid",
> -		.acpi_match_table = ACPI_PTR(vmgenid_ids),
> +		.acpi_match_table = ACPI_PTR(vmgenid_acpi_ids),
> +		.of_match_table = vmgenid_of_ids,
>  		.owner = THIS_MODULE,
>  	},
>  };
> @@ -144,7 +223,8 @@ static void vmgenid_platform_device_exit(void)
>  module_init(vmgenid_platform_device_init)
>  module_exit(vmgenid_platform_device_exit)
>  
> -MODULE_DEVICE_TABLE(acpi, vmgenid_ids);
> +MODULE_DEVICE_TABLE(acpi, vmgenid_acpi_ids);
> +MODULE_DEVICE_TABLE(of, vmgenid_of_ids);

MODULE_DEVICE_TABLE goes immediately after the table.


Best regards,
Krzysztof