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, 100 insertions, 0 deletions

diff --git a/drivers/clk/mmp/reset.c b/drivers/clk/mmp/reset.c
new file mode 100644
index 000000000..1e4e105ef
--- /dev/null
+++ b/drivers/clk/mmp/reset.c
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/reset-controller.h>
+
+#include "reset.h"
+
+#define rcdev_to_unit(rcdev) container_of(rcdev, struct mmp_clk_reset_unit, rcdev)
+
+static int mmp_of_reset_xlate(struct reset_controller_dev *rcdev,
+			  const struct of_phandle_args *reset_spec)
+{
+	struct mmp_clk_reset_unit *unit = rcdev_to_unit(rcdev);
+	struct mmp_clk_reset_cell *cell;
+	int i;
+
+	if (WARN_ON(reset_spec->args_count != rcdev->of_reset_n_cells))
+		return -EINVAL;
+
+	for (i = 0; i < rcdev->nr_resets; i++) {
+		cell = &unit->cells[i];
+		if (cell->clk_id == reset_spec->args[0])
+			break;
+	}
+
+	if (i == rcdev->nr_resets)
+		return -EINVAL;
+
+	return i;
+}
+
+static int mmp_clk_reset_assert(struct reset_controller_dev *rcdev,
+				unsigned long id)
+{
+	struct mmp_clk_reset_unit *unit = rcdev_to_unit(rcdev);
+	struct mmp_clk_reset_cell *cell;
+	unsigned long flags = 0;
+	u32 val;
+
+	cell = &unit->cells[id];
+	if (cell->lock)
+		spin_lock_irqsave(cell->lock, flags);
+
+	val = readl(cell->reg);
+	val |= cell->bits;
+	writel(val, cell->reg);
+
+	if (cell->lock)
+		spin_unlock_irqrestore(cell->lock, flags);
+
+	return 0;
+}
+
+static int mmp_clk_reset_deassert(struct reset_controller_dev *rcdev,
+				unsigned long id)
+{
+	struct mmp_clk_reset_unit *unit = rcdev_to_unit(rcdev);
+	struct mmp_clk_reset_cell *cell;
+	unsigned long flags = 0;
+	u32 val;
+
+	cell = &unit->cells[id];
+	if (cell->lock)
+		spin_lock_irqsave(cell->lock, flags);
+
+	val = readl(cell->reg);
+	val &= ~cell->bits;
+	writel(val, cell->reg);
+
+	if (cell->lock)
+		spin_unlock_irqrestore(cell->lock, flags);
+
+	return 0;
+}
+
+static const struct reset_control_ops mmp_clk_reset_ops = {
+	.assert		= mmp_clk_reset_assert,
+	.deassert	= mmp_clk_reset_deassert,
+};
+
+void mmp_clk_reset_register(struct device_node *np,
+			struct mmp_clk_reset_cell *cells, int nr_resets)
+{
+	struct mmp_clk_reset_unit *unit;
+
+	unit = kzalloc_obj(*unit);
+	if (!unit)
+		return;
+
+	unit->cells = cells;
+	unit->rcdev.of_reset_n_cells = 1;
+	unit->rcdev.nr_resets = nr_resets;
+	unit->rcdev.ops = &mmp_clk_reset_ops;
+	unit->rcdev.of_node = np;
+	unit->rcdev.of_xlate = mmp_of_reset_xlate;
+
+	reset_controller_register(&unit->rcdev);
+}