From e07606713a908eee8099883c8c830ebe33aaf748 Mon Sep 17 00:00:00 2001 From: Sudan Landge Date: Wed, 17 Apr 2024 12:40:42 +0200 Subject: [PATCH 1/3] virt: vmgenid: change implementation to use a platform driver Re-implement vmgenid as a platform driver in preparation for adding devicetree bindings support in next commits. Signed-off-by: Sudan Landge Reviewed-by: Alexander Graf Tested-by: Babis Chalios [Jason: - Small style cleanups and refactoring.] Signed-off-by: Jason A. Donenfeld --- drivers/virt/vmgenid.c | 99 +++++++++++++++++++++++++++--------------- 1 file changed, 65 insertions(+), 34 deletions(-) diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c index a1c467a0e9f7..0522107f9bee 100644 --- a/drivers/virt/vmgenid.c +++ b/drivers/virt/vmgenid.c @@ -7,9 +7,10 @@ * information to random.c. */ +#include #include #include -#include +#include #include ACPI_MODULE_NAME("vmgenid"); @@ -21,19 +22,41 @@ struct vmgenid_state { u8 this_id[VMGENID_SIZE]; }; -static int vmgenid_add(struct acpi_device *device) +static void vmgenid_notify(struct device *device) { + struct vmgenid_state *state = device->driver_data; + u8 old_id[VMGENID_SIZE]; + + memcpy(old_id, state->this_id, sizeof(old_id)); + memcpy(state->this_id, state->next_id, sizeof(state->this_id)); + if (!memcmp(old_id, state->this_id, sizeof(old_id))) + return; + add_vmfork_randomness(state->this_id, sizeof(state->this_id)); +} + +static void setup_vmgenid_state(struct vmgenid_state *state, void *virt_addr) +{ + state->next_id = virt_addr; + memcpy(state->this_id, state->next_id, sizeof(state->this_id)); + add_device_randomness(state->this_id, sizeof(state->this_id)); +} + +static void vmgenid_acpi_handler(acpi_handle __always_unused handle, + u32 __always_unused event, void *dev) +{ + vmgenid_notify(dev); +} + +static int vmgenid_add_acpi(struct device *dev, struct vmgenid_state *state) +{ + struct acpi_device *device = ACPI_COMPANION(dev); struct acpi_buffer parsed = { ACPI_ALLOCATE_BUFFER }; - struct vmgenid_state *state; union acpi_object *obj; phys_addr_t phys_addr; acpi_status status; + void *virt_addr; int ret = 0; - state = devm_kmalloc(&device->dev, sizeof(*state), GFP_KERNEL); - if (!state) - return -ENOMEM; - status = acpi_evaluate_object(device->handle, "ADDR", NULL, &parsed); if (ACPI_FAILURE(status)) { ACPI_EXCEPTION((AE_INFO, status, "Evaluating ADDR")); @@ -49,53 +72,61 @@ static int vmgenid_add(struct acpi_device *device) phys_addr = (obj->package.elements[0].integer.value << 0) | (obj->package.elements[1].integer.value << 32); - state->next_id = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB); - if (IS_ERR(state->next_id)) { - ret = PTR_ERR(state->next_id); + + virt_addr = devm_memremap(&device->dev, phys_addr, VMGENID_SIZE, MEMREMAP_WB); + if (IS_ERR(virt_addr)) { + ret = PTR_ERR(virt_addr); + goto out; + } + setup_vmgenid_state(state, virt_addr); + + status = acpi_install_notify_handler(device->handle, ACPI_DEVICE_NOTIFY, + vmgenid_acpi_handler, dev); + if (ACPI_FAILURE(status)) { + ret = -ENODEV; goto out; } - memcpy(state->this_id, state->next_id, sizeof(state->this_id)); - add_device_randomness(state->this_id, sizeof(state->this_id)); - - device->driver_data = state; - + dev->driver_data = state; out: ACPI_FREE(parsed.pointer); return ret; } -static void vmgenid_notify(struct acpi_device *device, u32 event) +static int vmgenid_add(struct platform_device *pdev) { - struct vmgenid_state *state = acpi_driver_data(device); - u8 old_id[VMGENID_SIZE]; + struct device *dev = &pdev->dev; + struct vmgenid_state *state; + int ret; - memcpy(old_id, state->this_id, sizeof(old_id)); - memcpy(state->this_id, state->next_id, sizeof(state->this_id)); - if (!memcmp(old_id, state->this_id, sizeof(old_id))) - return; - add_vmfork_randomness(state->this_id, sizeof(state->this_id)); + state = devm_kmalloc(dev, sizeof(*state), GFP_KERNEL); + if (!state) + return -ENOMEM; + + ret = vmgenid_add_acpi(dev, state); + + if (ret < 0) + devm_kfree(dev, state); + return ret; } -static const struct acpi_device_id vmgenid_ids[] = { +static const struct acpi_device_id vmgenid_acpi_ids[] = { { "VMGENCTR", 0 }, { "VM_GEN_COUNTER", 0 }, { } }; +MODULE_DEVICE_TABLE(acpi, vmgenid_acpi_ids); -static struct acpi_driver vmgenid_driver = { - .name = "vmgenid", - .ids = vmgenid_ids, - .owner = THIS_MODULE, - .ops = { - .add = vmgenid_add, - .notify = vmgenid_notify - } +static struct platform_driver vmgenid_plaform_driver = { + .probe = vmgenid_add, + .driver = { + .name = "vmgenid", + .acpi_match_table = vmgenid_acpi_ids, + }, }; -module_acpi_driver(vmgenid_driver); +module_platform_driver(vmgenid_plaform_driver) -MODULE_DEVICE_TABLE(acpi, vmgenid_ids); MODULE_DESCRIPTION("Virtual Machine Generation ID"); MODULE_LICENSE("GPL v2"); MODULE_AUTHOR("Jason A. Donenfeld "); From a4aded1ff5759a2ab754699c0408be79c9ebdda4 Mon Sep 17 00:00:00 2001 From: Sudan Landge Date: Wed, 17 Apr 2024 12:40:45 +0200 Subject: [PATCH 2/3] dt-bindings: rng: Add vmgenid support Virtual Machine Generation ID driver was introduced in commit af6b54e2b5ba ("virt: vmgenid: notify RNG of VM fork and supply generation ID"), as an ACPI only device. VMGenID specification http://go.microsoft.com/fwlink/?LinkId=260709 defines a mechanism for the BIOS/hypervisors to communicate to the virtual machine that it is executed with a different configuration (e.g. snapshot execution or creation from a template). The guest operating system can use the notification for various purposes such as re-initializing its random number generator etc. As per the specs, hypervisor should provide a globally unique identified, or GUID via ACPI. This patch tries to mimic the mechanism to provide the same functionality which is for a hypervisor/BIOS to notify the virtual machine when it is executed with a different configuration. As part of this support the devicetree bindings requires the hypervisors or BIOS to provide a memory address which holds the GUID and an IRQ which is used to notify when there is a change in the GUID. The memory exposed in the DT should follow the rules defined in the vmgenid spec mentioned above. Reason for this change: Chosing ACPI or devicetree is an intrinsic part of an hypervisor design. Without going into details of why a hypervisor would chose DT over ACPI, we would like to highlight that the hypervisors that have chose devicetree and now want to make use of the vmgenid functionality cannot do so today because vmgenid is an ACPI only device. This forces these hypervisors to change their design which could have undesirable impacts on their use-cases, test-scenarios etc. The point of vmgenid is to provide a mechanism to discover a GUID when the execution state of a virtual machine changes and the simplest way to do it is pass a memory location and an interrupt via devicetree. It would complicate things unnecessarily if instead of using devicetree, we try to implement a new protocol or modify other protocols to somehow provide the same functionility. We believe that adding a devicetree binding for vmgenid is a simpler, better alternative to provide the same functionality and will allow such hypervisors as mentioned above to continue using devicetree. More references to the vmgenid specs are found below. Signed-off-by: Sudan Landge Reviewed-by: Rob Herring Reviewed-by: Alexander Graf Link: https://www.qemu.org/docs/master/specs/vmgenid.html Link: https://learn.microsoft.com/en-us/windows/win32/hyperv_v2/virtual-machine-generation-identifier Signed-off-by: Jason A. Donenfeld --- .../bindings/rng/microsoft,vmgenid.yaml | 49 +++++++++++++++++++ MAINTAINERS | 1 + 2 files changed, 50 insertions(+) create mode 100644 Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml diff --git a/Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml b/Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml new file mode 100644 index 000000000000..8f20dee93e7e --- /dev/null +++ b/Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml @@ -0,0 +1,49 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/rng/microsoft,vmgenid.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Virtual Machine Generation ID + +maintainers: + - Jason A. Donenfeld + +description: + Firmwares or hypervisors can use this devicetree to describe an + interrupt and a shared resource to inject a Virtual Machine Generation ID. + Virtual Machine Generation ID is a globally unique identifier (GUID) and + the devicetree binding follows VMGenID specification defined in + http://go.microsoft.com/fwlink/?LinkId=260709. + +properties: + compatible: + const: microsoft,vmgenid + + reg: + description: + Specifies a 16-byte VMGenID in endianness-agnostic hexadecimal format. + maxItems: 1 + + interrupts: + description: + Interrupt used to notify that a new VMGenID is available. + maxItems: 1 + +required: + - compatible + - reg + - interrupts + +additionalProperties: false + +examples: + - | + #include + rng@80000000 { + compatible = "microsoft,vmgenid"; + reg = <0x80000000 0x1000>; + interrupts = ; + }; + +... diff --git a/MAINTAINERS b/MAINTAINERS index a86685c57e12..c70c14d6c635 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -18467,6 +18467,7 @@ M: "Theodore Ts'o" M: Jason A. Donenfeld S: Maintained T: git https://git.kernel.org/pub/scm/linux/kernel/git/crng/random.git +F: Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml F: drivers/char/random.c F: drivers/virt/vmgenid.c From 7b1bcd6b50a615671d4dcb0ad0378a2660a1a368 Mon Sep 17 00:00:00 2001 From: Sudan Landge Date: Wed, 17 Apr 2024 12:40:46 +0200 Subject: [PATCH 3/3] 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 Reviewed-by: Alexander Graf Tested-by: Babis Chalios [Jason: - Small style cleanups and refactoring. - Re-work ACPI conditionalization. ] Signed-off-by: Jason A. Donenfeld --- drivers/virt/Kconfig | 1 - drivers/virt/vmgenid.c | 53 ++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 51 insertions(+), 3 deletions(-) diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig index 40129b6f0eca..d8c848cf09a6 100644 --- 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 0522107f9bee..66135eac3abf 100644 --- a/drivers/virt/vmgenid.c +++ b/drivers/virt/vmgenid.c @@ -2,12 +2,13 @@ /* * Copyright (C) 2022 Jason A. Donenfeld . 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 +#include #include #include #include @@ -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, }, };