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Message-ID: <e4cbb6ab-975a-4d91-9bde-6976b4d84eba@amazon.co.uk>
Date: Fri, 19 Apr 2024 14:29:45 +0100
From: "Landge, Sudan" <sudanl@...zon.co.uk>
To: "Jason A. Donenfeld" <Jason@...c4.com>, <tytso@....edu>,
<robh@...nel.org>, <krzk@...nel.org>, <conor+dt@...nel.org>,
<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<sudanl@...zon.com>, <graf@...zon.com>, <dwmw@...zon.co.uk>,
<krzysztof.kozlowski@...aro.org>, <bchalios@...zon.es>,
<xmarcalx@...zon.co.uk>
Subject: Re: [PATCH v7 3/3] virt: vmgenid: add support for devicetree bindings
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@...zon.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@...zon.com>
> Reviewed-by: Alexander Graf <graf@...zon.com>
> [Jason: - Small style cleanups and refactoring.
> - Fold in Kconfig OF dependency and ACPI conditionalization. ]
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.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@...c4.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.
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