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, 135 insertions, 0 deletions

diff --git a/drivers/input/misc/e3x0-button.c b/drivers/input/misc/e3x0-button.c
new file mode 100644
index 000000000..5bd527117
--- /dev/null
+++ b/drivers/input/misc/e3x0-button.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2014, National Instruments Corp. All rights reserved.
+ *
+ * Driver for NI Ettus Research USRP E3x0 Button Driver
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+
+static irqreturn_t e3x0_button_release_handler(int irq, void *data)
+{
+	struct input_dev *idev = data;
+
+	input_report_key(idev, KEY_POWER, 0);
+	input_sync(idev);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t e3x0_button_press_handler(int irq, void *data)
+{
+	struct input_dev *idev = data;
+
+	input_report_key(idev, KEY_POWER, 1);
+	pm_wakeup_event(idev->dev.parent, 0);
+	input_sync(idev);
+
+	return IRQ_HANDLED;
+}
+
+static int e3x0_button_suspend(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+
+	if (device_may_wakeup(dev))
+		enable_irq_wake(platform_get_irq_byname(pdev, "press"));
+
+	return 0;
+}
+
+static int e3x0_button_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+
+	if (device_may_wakeup(dev))
+		disable_irq_wake(platform_get_irq_byname(pdev, "press"));
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(e3x0_button_pm_ops,
+				e3x0_button_suspend, e3x0_button_resume);
+
+static int e3x0_button_probe(struct platform_device *pdev)
+{
+	struct input_dev *input;
+	int irq_press, irq_release;
+	int error;
+
+	irq_press = platform_get_irq_byname(pdev, "press");
+	if (irq_press < 0)
+		return irq_press;
+
+	irq_release = platform_get_irq_byname(pdev, "release");
+	if (irq_release < 0)
+		return irq_release;
+
+	input = devm_input_allocate_device(&pdev->dev);
+	if (!input)
+		return -ENOMEM;
+
+	input->name = "NI Ettus Research USRP E3x0 Button Driver";
+	input->phys = "e3x0_button/input0";
+	input->dev.parent = &pdev->dev;
+
+	input_set_capability(input, EV_KEY, KEY_POWER);
+
+	error = devm_request_irq(&pdev->dev, irq_press,
+				 e3x0_button_press_handler, 0,
+				 "e3x0-button", input);
+	if (error) {
+		dev_err(&pdev->dev, "Failed to request 'press' IRQ#%d: %d\n",
+			irq_press, error);
+		return error;
+	}
+
+	error = devm_request_irq(&pdev->dev, irq_release,
+				 e3x0_button_release_handler, 0,
+				 "e3x0-button", input);
+	if (error) {
+		dev_err(&pdev->dev, "Failed to request 'release' IRQ#%d: %d\n",
+			irq_release, error);
+		return error;
+	}
+
+	error = input_register_device(input);
+	if (error) {
+		dev_err(&pdev->dev, "Can't register input device: %d\n", error);
+		return error;
+	}
+
+	device_init_wakeup(&pdev->dev, 1);
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id e3x0_button_match[] = {
+	{ .compatible = "ettus,e3x0-button", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, e3x0_button_match);
+#endif
+
+static struct platform_driver e3x0_button_driver = {
+	.driver		= {
+		.name	= "e3x0-button",
+		.of_match_table = of_match_ptr(e3x0_button_match),
+		.pm	= pm_sleep_ptr(&e3x0_button_pm_ops),
+	},
+	.probe		= e3x0_button_probe,
+};
+
+module_platform_driver(e3x0_button_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Moritz Fischer <moritz.fischer@ettus.com>");
+MODULE_DESCRIPTION("NI Ettus Research USRP E3x0 Button driver");
+MODULE_ALIAS("platform:e3x0-button");