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, 112 insertions, 0 deletions

diff --git a/drivers/input/misc/cpcap-pwrbutton.c b/drivers/input/misc/cpcap-pwrbutton.c
new file mode 100644
index 000000000..85cddb847
--- /dev/null
+++ b/drivers/input/misc/cpcap-pwrbutton.c
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * CPCAP Power Button Input Driver
+ *
+ * Copyright (C) 2017 Sebastian Reichel <sre@kernel.org>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/regmap.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/motorola-cpcap.h>
+
+#define CPCAP_IRQ_ON 23
+#define CPCAP_IRQ_ON_BITMASK (1 << (CPCAP_IRQ_ON % 16))
+
+struct cpcap_power_button {
+	struct regmap *regmap;
+	struct input_dev *idev;
+	struct device *dev;
+};
+
+static irqreturn_t powerbutton_irq(int irq, void *_button)
+{
+	struct cpcap_power_button *button = _button;
+	int val;
+
+	val = cpcap_sense_virq(button->regmap, irq);
+	if (val < 0) {
+		dev_err(button->dev, "irq read failed: %d", val);
+		return IRQ_HANDLED;
+	}
+
+	pm_wakeup_event(button->dev, 0);
+	input_report_key(button->idev, KEY_POWER, val);
+	input_sync(button->idev);
+
+	return IRQ_HANDLED;
+}
+
+static int cpcap_power_button_probe(struct platform_device *pdev)
+{
+	struct cpcap_power_button *button;
+	int irq;
+	int err;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	button = devm_kmalloc(&pdev->dev, sizeof(*button), GFP_KERNEL);
+	if (!button)
+		return -ENOMEM;
+
+	button->idev = devm_input_allocate_device(&pdev->dev);
+	if (!button->idev)
+		return -ENOMEM;
+
+	button->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!button->regmap)
+		return -ENODEV;
+
+	button->dev = &pdev->dev;
+
+	button->idev->name = "cpcap-pwrbutton";
+	button->idev->phys = "cpcap-pwrbutton/input0";
+	input_set_capability(button->idev, EV_KEY, KEY_POWER);
+
+	err = devm_request_threaded_irq(&pdev->dev, irq, NULL,
+		powerbutton_irq, IRQF_ONESHOT, "cpcap_pwrbutton", button);
+	if (err < 0) {
+		dev_err(&pdev->dev, "IRQ request failed: %d\n", err);
+		return err;
+	}
+
+	err = input_register_device(button->idev);
+	if (err) {
+		dev_err(&pdev->dev, "Input register failed: %d\n", err);
+		return err;
+	}
+
+	device_init_wakeup(&pdev->dev, true);
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id cpcap_pwrbutton_dt_match_table[] = {
+	{ .compatible = "motorola,cpcap-pwrbutton" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, cpcap_pwrbutton_dt_match_table);
+#endif
+
+static struct platform_driver cpcap_power_button_driver = {
+	.probe		= cpcap_power_button_probe,
+	.driver		= {
+		.name	= "cpcap-pwrbutton",
+		.of_match_table = of_match_ptr(cpcap_pwrbutton_dt_match_table),
+	},
+};
+module_platform_driver(cpcap_power_button_driver);
+
+MODULE_ALIAS("platform:cpcap-pwrbutton");
+MODULE_DESCRIPTION("CPCAP Power Button");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sebastian Reichel <sre@kernel.org>");