KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 195 insertions, 0 deletions

diff --git a/drivers/acpi/evged.c b/drivers/acpi/evged.c
new file mode 100644
index 000000000..5c35cbc7f
--- /dev/null
+++ b/drivers/acpi/evged.c
@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic Event Device for ACPI.
+ *
+ * Copyright (c) 2016, The Linux Foundation. All rights reserved.
+ *
+ * Generic Event Device allows platforms to handle interrupts in ACPI
+ * ASL statements. It follows very similar to  _EVT method approach
+ * from GPIO events. All interrupts are listed in _CRS and the handler
+ * is written in _EVT method. Here is an example.
+ *
+ * Device (GED0)
+ * {
+ *
+ *     Name (_HID, "ACPI0013")
+ *     Name (_UID, 0)
+ *     Method (_CRS, 0x0, Serialized)
+ *     {
+ *		Name (RBUF, ResourceTemplate ()
+ *		{
+ *		Interrupt(ResourceConsumer, Edge, ActiveHigh, Shared, , , )
+ *		{123}
+ *		}
+ *     })
+ *
+ *     Method (_EVT, 1) {
+ *             if (Lequal(123, Arg0))
+ *             {
+ *             }
+ *     }
+ * }
+ */
+
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/list.h>
+#include <linux/platform_device.h>
+#include <linux/acpi.h>
+
+#define MODULE_NAME	"acpi-ged"
+
+struct acpi_ged_device {
+	struct device *dev;
+	struct list_head event_list;
+};
+
+struct acpi_ged_event {
+	struct list_head node;
+	struct device *dev;
+	unsigned int gsi;
+	unsigned int irq;
+	acpi_handle handle;
+};
+
+static irqreturn_t acpi_ged_irq_handler(int irq, void *data)
+{
+	struct acpi_ged_event *event = data;
+	acpi_status acpi_ret;
+
+	acpi_ret = acpi_execute_simple_method(event->handle, NULL, event->gsi);
+	if (ACPI_FAILURE(acpi_ret))
+		dev_err_once(event->dev, "IRQ method execution failed\n");
+
+	return IRQ_HANDLED;
+}
+
+static acpi_status acpi_ged_request_interrupt(struct acpi_resource *ares,
+					      void *context)
+{
+	struct acpi_ged_event *event;
+	unsigned int irq;
+	unsigned int gsi;
+	unsigned int irqflags = IRQF_ONESHOT;
+	struct acpi_ged_device *geddev = context;
+	struct device *dev = geddev->dev;
+	acpi_handle handle = ACPI_HANDLE(dev);
+	acpi_handle evt_handle;
+	struct resource r;
+	struct acpi_resource_irq *p = &ares->data.irq;
+	struct acpi_resource_extended_irq *pext = &ares->data.extended_irq;
+	char ev_name[5];
+	u8 trigger;
+
+	if (ares->type == ACPI_RESOURCE_TYPE_END_TAG)
+		return AE_OK;
+
+	if (!acpi_dev_resource_interrupt(ares, 0, &r)) {
+		dev_err(dev, "unable to parse IRQ resource\n");
+		return AE_ERROR;
+	}
+	if (ares->type == ACPI_RESOURCE_TYPE_IRQ) {
+		gsi = p->interrupts[0];
+		trigger = p->triggering;
+	} else {
+		gsi = pext->interrupts[0];
+		trigger = pext->triggering;
+	}
+
+	irq = r.start;
+
+	switch (gsi) {
+	case 0 ... 255:
+		sprintf(ev_name, "_%c%02X",
+			trigger == ACPI_EDGE_SENSITIVE ? 'E' : 'L', gsi);
+
+		if (ACPI_SUCCESS(acpi_get_handle(handle, ev_name, &evt_handle)))
+			break;
+		fallthrough;
+	default:
+		if (ACPI_SUCCESS(acpi_get_handle(handle, "_EVT", &evt_handle)))
+			break;
+
+		dev_err(dev, "cannot locate _EVT method\n");
+		return AE_ERROR;
+	}
+
+	event = devm_kzalloc(dev, sizeof(*event), GFP_KERNEL);
+	if (!event)
+		return AE_ERROR;
+
+	event->gsi = gsi;
+	event->dev = dev;
+	event->irq = irq;
+	event->handle = evt_handle;
+
+	if (r.flags & IORESOURCE_IRQ_SHAREABLE)
+		irqflags |= IRQF_SHARED;
+
+	if (request_threaded_irq(irq, NULL, acpi_ged_irq_handler,
+				 irqflags, "ACPI:Ged", event)) {
+		dev_err(dev, "failed to setup event handler for irq %u\n", irq);
+		return AE_ERROR;
+	}
+
+	dev_dbg(dev, "GED listening GSI %u @ IRQ %u\n", gsi, irq);
+	list_add_tail(&event->node, &geddev->event_list);
+	return AE_OK;
+}
+
+static int ged_probe(struct platform_device *pdev)
+{
+	struct acpi_ged_device *geddev;
+	acpi_status acpi_ret;
+
+	geddev = devm_kzalloc(&pdev->dev, sizeof(*geddev), GFP_KERNEL);
+	if (!geddev)
+		return -ENOMEM;
+
+	geddev->dev = &pdev->dev;
+	INIT_LIST_HEAD(&geddev->event_list);
+	acpi_ret = acpi_walk_resources(ACPI_HANDLE(&pdev->dev), "_CRS",
+				       acpi_ged_request_interrupt, geddev);
+	if (ACPI_FAILURE(acpi_ret)) {
+		dev_err(&pdev->dev, "unable to parse the _CRS record\n");
+		return -EINVAL;
+	}
+	platform_set_drvdata(pdev, geddev);
+
+	return 0;
+}
+
+static void ged_shutdown(struct platform_device *pdev)
+{
+	struct acpi_ged_device *geddev = platform_get_drvdata(pdev);
+	struct acpi_ged_event *event, *next;
+
+	list_for_each_entry_safe(event, next, &geddev->event_list, node) {
+		free_irq(event->irq, event);
+		list_del(&event->node);
+		dev_dbg(geddev->dev, "GED releasing GSI %u @ IRQ %u\n",
+			 event->gsi, event->irq);
+	}
+}
+
+static void ged_remove(struct platform_device *pdev)
+{
+	ged_shutdown(pdev);
+}
+
+static const struct acpi_device_id ged_acpi_ids[] = {
+	{"ACPI0013"},
+	{},
+};
+
+static struct platform_driver ged_driver = {
+	.probe = ged_probe,
+	.remove = ged_remove,
+	.shutdown = ged_shutdown,
+	.driver = {
+		.name = MODULE_NAME,
+		.acpi_match_table = ACPI_PTR(ged_acpi_ids),
+	},
+};
+builtin_platform_driver(ged_driver);