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, 122 insertions, 0 deletions

diff --git a/drivers/reset/reset-raspberrypi.c b/drivers/reset/reset-raspberrypi.c
new file mode 100644
index 000000000..fa23db554
--- /dev/null
+++ b/drivers/reset/reset-raspberrypi.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Raspberry Pi 4 firmware reset driver
+ *
+ * Copyright (C) 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
+ */
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <soc/bcm2835/raspberrypi-firmware.h>
+#include <dt-bindings/reset/raspberrypi,firmware-reset.h>
+
+struct rpi_reset {
+	struct reset_controller_dev rcdev;
+	struct rpi_firmware *fw;
+};
+
+static inline struct rpi_reset *to_rpi(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct rpi_reset, rcdev);
+}
+
+static int rpi_reset_reset(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct rpi_reset *priv = to_rpi(rcdev);
+	u32 dev_addr;
+	int ret;
+
+	switch (id) {
+	case RASPBERRYPI_FIRMWARE_RESET_ID_USB:
+		/*
+		 * The Raspberry Pi 4 gets its USB functionality from VL805, a
+		 * PCIe chip that implements xHCI. After a PCI reset, VL805's
+		 * firmware may either be loaded directly from an EEPROM or, if
+		 * not present, by the SoC's co-processor, VideoCore. rpi's
+		 * VideoCore OS contains both the non public firmware load
+		 * logic and the VL805 firmware blob. This triggers the
+		 * aforementioned process.
+		 *
+		 * The pci device address is expected is expected by the
+		 * firmware encoded like this:
+		 *
+		 *	PCI_BUS << 20 | PCI_SLOT << 15 | PCI_FUNC << 12
+		 *
+		 * But since rpi's PCIe is hardwired, we know the address in
+		 * advance.
+		 */
+		dev_addr = 0x100000;
+		ret = rpi_firmware_property(priv->fw, RPI_FIRMWARE_NOTIFY_XHCI_RESET,
+					    &dev_addr, sizeof(dev_addr));
+		if (ret)
+			return ret;
+
+		/* Wait for vl805 to startup */
+		usleep_range(200, 1000);
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct reset_control_ops rpi_reset_ops = {
+	.reset	= rpi_reset_reset,
+};
+
+static int rpi_reset_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct rpi_firmware *fw;
+	struct device_node *np;
+	struct rpi_reset *priv;
+
+	np = of_get_parent(dev->of_node);
+	if (!np) {
+		dev_err(dev, "Missing firmware node\n");
+		return -ENOENT;
+	}
+
+	fw = devm_rpi_firmware_get(&pdev->dev, np);
+	of_node_put(np);
+	if (!fw)
+		return -EPROBE_DEFER;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	dev_set_drvdata(dev, priv);
+
+	priv->fw = fw;
+	priv->rcdev.owner = THIS_MODULE;
+	priv->rcdev.nr_resets = RASPBERRYPI_FIRMWARE_RESET_NUM_IDS;
+	priv->rcdev.ops = &rpi_reset_ops;
+	priv->rcdev.of_node = dev->of_node;
+
+	return devm_reset_controller_register(dev, &priv->rcdev);
+}
+
+static const struct of_device_id rpi_reset_of_match[] = {
+	{ .compatible = "raspberrypi,firmware-reset" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, rpi_reset_of_match);
+
+static struct platform_driver rpi_reset_driver = {
+	.probe	= rpi_reset_probe,
+	.driver	= {
+		.name = "raspberrypi-reset",
+		.of_match_table = rpi_reset_of_match,
+	},
+};
+module_platform_driver(rpi_reset_driver);
+
+MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
+MODULE_DESCRIPTION("Raspberry Pi 4 firmware reset driver");
+MODULE_LICENSE("GPL");