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

Krzysztof Kozlowski
2024-03-19T15:30:59Z

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@amazon.com>
> ---
> 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@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.
> */
> @@ -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