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, 80 insertions, 0 deletions

diff --git a/drivers/clk/sprd/div.c b/drivers/clk/sprd/div.c
new file mode 100644
index 000000000..cd57163a7
--- /dev/null
+++ b/drivers/clk/sprd/div.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Spreadtrum divider clock driver
+//
+// Copyright (C) 2017 Spreadtrum, Inc.
+// Author: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
+
+#include <linux/clk-provider.h>
+
+#include "div.h"
+
+static int sprd_div_determine_rate(struct clk_hw *hw,
+				   struct clk_rate_request *req)
+{
+	struct sprd_div *cd = hw_to_sprd_div(hw);
+
+	return divider_determine_rate(&cd->common.hw, req, NULL, cd->div.width, 0);
+}
+
+unsigned long sprd_div_helper_recalc_rate(struct sprd_clk_common *common,
+					  const struct sprd_div_internal *div,
+					  unsigned long parent_rate)
+{
+	unsigned long val;
+	unsigned int reg;
+
+	regmap_read(common->regmap, common->reg + div->offset, &reg);
+	val = reg >> div->shift;
+	val &= (1 << div->width) - 1;
+
+	return divider_recalc_rate(&common->hw, parent_rate, val, NULL, 0,
+				   div->width);
+}
+EXPORT_SYMBOL_GPL(sprd_div_helper_recalc_rate);
+
+static unsigned long sprd_div_recalc_rate(struct clk_hw *hw,
+					  unsigned long parent_rate)
+{
+	struct sprd_div *cd = hw_to_sprd_div(hw);
+
+	return sprd_div_helper_recalc_rate(&cd->common, &cd->div, parent_rate);
+}
+
+int sprd_div_helper_set_rate(const struct sprd_clk_common *common,
+			     const struct sprd_div_internal *div,
+			     unsigned long rate,
+			     unsigned long parent_rate)
+{
+	unsigned long val;
+	unsigned int reg;
+
+	val = divider_get_val(rate, parent_rate, NULL,
+			      div->width, 0);
+
+	regmap_read(common->regmap, common->reg + div->offset, &reg);
+	reg &= ~GENMASK(div->width + div->shift - 1, div->shift);
+
+	regmap_write(common->regmap, common->reg + div->offset,
+			  reg | (val << div->shift));
+
+	return 0;
+
+}
+EXPORT_SYMBOL_GPL(sprd_div_helper_set_rate);
+
+static int sprd_div_set_rate(struct clk_hw *hw, unsigned long rate,
+			     unsigned long parent_rate)
+{
+	struct sprd_div *cd = hw_to_sprd_div(hw);
+
+	return sprd_div_helper_set_rate(&cd->common, &cd->div,
+					rate, parent_rate);
+}
+
+const struct clk_ops sprd_div_ops = {
+	.recalc_rate = sprd_div_recalc_rate,
+	.determine_rate = sprd_div_determine_rate,
+	.set_rate = sprd_div_set_rate,
+};
+EXPORT_SYMBOL_GPL(sprd_div_ops);