virt: vmgenid: add support for devicetree bindings

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>

diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
index 40129b6f0eca41ced6c6213776571a5ae8374ebe..d8c848cf09a6afad65b28be20f5fd7e90a0c5307 100644 (file)
--- a/drivers/virt/Kconfig
+++ b/drivers/virt/Kconfig
@@ -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

diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c
index 0522107f9beebb24c14e790ebf6154f815405c40..66135eac3abffa3b65e39efc97c217a3da13c287 100644 (file)
--- 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 @@ 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,
        },
 };