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virt: vmgenid: add support for devicetree bindings

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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 is no longer ACPI-dependent, remove the dependency from
Kconfig and protect the ACPI code with a single ifdef.

Signed-off-by: Sudan Landge <sudanl@amazon.com>
Reviewed-by: Alexander Graf <graf@amazon.com>
Tested-by: Babis Chalios <bchalios@amazon.es>
[Jason: - Small style cleanups and refactoring.
        - Re-work ACPI conditionalization. ]
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Sudan Landge 2024-04-17 12:40:46 +02:00 committed by Jason A. Donenfeld
parent a4aded1ff5
commit 7b1bcd6b50
2 changed files with 51 additions and 3 deletions
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1
drivers/virt/Kconfig
View File

@ -16,7 +16,6 @@ if VIRT_DRIVERS
config VMGENID
tristate "Virtual Machine Generation ID driver"
default y
depends on ACPI
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

53
drivers/virt/vmgenid.c
View File

@ -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 @@ out:
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 < 0)
return ret;
ret = devm_request_irq(&pdev->dev, ret, vmgenid_of_irq_handler,
IRQF_SHARED, "vmgenid", &pdev->dev);
if (ret < 0)
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 < 0)
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,
},
};