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, 133 insertions, 0 deletions

diff --git a/drivers/reset/reset-bcm6345.c b/drivers/reset/reset-bcm6345.c
new file mode 100644
index 000000000..441d9dd76
--- /dev/null
+++ b/drivers/reset/reset-bcm6345.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * BCM6345 Reset Controller Driver
+ *
+ * Copyright (C) 2020 Álvaro Fernández Rojas <noltari@gmail.com>
+ */
+
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+
+#define BCM6345_RESET_NUM		32
+#define BCM6345_RESET_SLEEP_MIN_US	10000
+#define BCM6345_RESET_SLEEP_MAX_US	20000
+
+struct bcm6345_reset {
+	struct reset_controller_dev rcdev;
+	void __iomem *base;
+	spinlock_t lock;
+};
+
+static inline struct bcm6345_reset *
+to_bcm6345_reset(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct bcm6345_reset, rcdev);
+}
+
+static int bcm6345_reset_update(struct reset_controller_dev *rcdev,
+				unsigned long id, bool assert)
+{
+	struct bcm6345_reset *bcm6345_reset = to_bcm6345_reset(rcdev);
+	unsigned long flags;
+	uint32_t val;
+
+	spin_lock_irqsave(&bcm6345_reset->lock, flags);
+	val = __raw_readl(bcm6345_reset->base);
+	if (assert)
+		val &= ~BIT(id);
+	else
+		val |= BIT(id);
+	__raw_writel(val, bcm6345_reset->base);
+	spin_unlock_irqrestore(&bcm6345_reset->lock, flags);
+
+	return 0;
+}
+
+static int bcm6345_reset_assert(struct reset_controller_dev *rcdev,
+				unsigned long id)
+{
+	return bcm6345_reset_update(rcdev, id, true);
+}
+
+static int bcm6345_reset_deassert(struct reset_controller_dev *rcdev,
+				  unsigned long id)
+{
+	return bcm6345_reset_update(rcdev, id, false);
+}
+
+static int bcm6345_reset_reset(struct reset_controller_dev *rcdev,
+			       unsigned long id)
+{
+	bcm6345_reset_update(rcdev, id, true);
+	usleep_range(BCM6345_RESET_SLEEP_MIN_US,
+		     BCM6345_RESET_SLEEP_MAX_US);
+
+	bcm6345_reset_update(rcdev, id, false);
+	/*
+	 * Ensure component is taken out reset state by sleeping also after
+	 * deasserting the reset. Otherwise, the component may not be ready
+	 * for operation.
+	 */
+	usleep_range(BCM6345_RESET_SLEEP_MIN_US,
+		     BCM6345_RESET_SLEEP_MAX_US);
+
+	return 0;
+}
+
+static int bcm6345_reset_status(struct reset_controller_dev *rcdev,
+				unsigned long id)
+{
+	struct bcm6345_reset *bcm6345_reset = to_bcm6345_reset(rcdev);
+
+	return !(__raw_readl(bcm6345_reset->base) & BIT(id));
+}
+
+static const struct reset_control_ops bcm6345_reset_ops = {
+	.assert = bcm6345_reset_assert,
+	.deassert = bcm6345_reset_deassert,
+	.reset = bcm6345_reset_reset,
+	.status = bcm6345_reset_status,
+};
+
+static int bcm6345_reset_probe(struct platform_device *pdev)
+{
+	struct bcm6345_reset *bcm6345_reset;
+
+	bcm6345_reset = devm_kzalloc(&pdev->dev,
+				     sizeof(*bcm6345_reset), GFP_KERNEL);
+	if (!bcm6345_reset)
+		return -ENOMEM;
+
+	bcm6345_reset->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(bcm6345_reset->base))
+		return PTR_ERR(bcm6345_reset->base);
+
+	spin_lock_init(&bcm6345_reset->lock);
+	bcm6345_reset->rcdev.ops = &bcm6345_reset_ops;
+	bcm6345_reset->rcdev.owner = THIS_MODULE;
+	bcm6345_reset->rcdev.of_node = pdev->dev.of_node;
+	bcm6345_reset->rcdev.of_reset_n_cells = 1;
+	bcm6345_reset->rcdev.nr_resets = BCM6345_RESET_NUM;
+
+	return devm_reset_controller_register(&pdev->dev,
+					      &bcm6345_reset->rcdev);
+}
+
+static const struct of_device_id bcm6345_reset_of_match[] = {
+	{ .compatible = "brcm,bcm6345-reset" },
+	{ .compatible = "brcm,bcm63xx-ephy-ctrl" },
+	{ /* sentinel */ },
+};
+
+static struct platform_driver bcm6345_reset_driver = {
+	.probe = bcm6345_reset_probe,
+	.driver	= {
+		.name = "bcm6345-reset",
+		.of_match_table = bcm6345_reset_of_match,
+		.suppress_bind_attrs = true,
+	},
+};
+builtin_platform_driver(bcm6345_reset_driver);