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, 142 insertions, 0 deletions

diff --git a/drivers/clk/tegra/cvb.c b/drivers/clk/tegra/cvb.c
new file mode 100644
index 000000000..a7fdc7622
--- /dev/null
+++ b/drivers/clk/tegra/cvb.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Utility functions for parsing Tegra CVB voltage tables
+ *
+ * Copyright (C) 2012-2019 NVIDIA Corporation.  All rights reserved.
+ */
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/pm_opp.h>
+
+#include "cvb.h"
+
+/* cvb_mv = ((c2 * speedo / s_scale + c1) * speedo / s_scale + c0) */
+static inline int get_cvb_voltage(int speedo, int s_scale,
+				  const struct cvb_coefficients *cvb)
+{
+	int mv;
+
+	/* apply only speedo scale: output mv = cvb_mv * v_scale */
+	mv = DIV_ROUND_CLOSEST(cvb->c2 * speedo, s_scale);
+	mv = DIV_ROUND_CLOSEST((mv + cvb->c1) * speedo, s_scale) + cvb->c0;
+	return mv;
+}
+
+static int round_cvb_voltage(int mv, int v_scale,
+			     const struct rail_alignment *align)
+{
+	/* combined: apply voltage scale and round to cvb alignment step */
+	int uv;
+	int step = (align->step_uv ? : 1000) * v_scale;
+	int offset = align->offset_uv * v_scale;
+
+	uv = max(mv * 1000, offset) - offset;
+	uv = DIV_ROUND_UP(uv, step) * align->step_uv + align->offset_uv;
+	return uv / 1000;
+}
+
+enum {
+	DOWN,
+	UP
+};
+
+static int round_voltage(int mv, const struct rail_alignment *align, int up)
+{
+	if (align->step_uv) {
+		int uv;
+
+		uv = max(mv * 1000, align->offset_uv) - align->offset_uv;
+		uv = (uv + (up ? align->step_uv - 1 : 0)) / align->step_uv;
+		return (uv * align->step_uv + align->offset_uv) / 1000;
+	}
+	return mv;
+}
+
+static int build_opp_table(struct device *dev, const struct cvb_table *table,
+			   struct rail_alignment *align,
+			   int speedo_value, unsigned long max_freq)
+{
+	int i, ret, dfll_mv, min_mv, max_mv;
+
+	min_mv = round_voltage(table->min_millivolts, align, UP);
+	max_mv = round_voltage(table->max_millivolts, align, DOWN);
+
+	for (i = 0; i < MAX_DVFS_FREQS; i++) {
+		const struct cvb_table_freq_entry *entry = &table->entries[i];
+
+		if (!entry->freq || (entry->freq > max_freq))
+			break;
+
+		dfll_mv = get_cvb_voltage(speedo_value, table->speedo_scale,
+					  &entry->coefficients);
+		dfll_mv = round_cvb_voltage(dfll_mv, table->voltage_scale,
+					    align);
+		dfll_mv = clamp(dfll_mv, min_mv, max_mv);
+
+		ret = dev_pm_opp_add(dev, entry->freq, dfll_mv * 1000);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * tegra_cvb_add_opp_table - build OPP table from Tegra CVB tables
+ * @dev: the struct device * for which the OPP table is built
+ * @tables: array of CVB tables
+ * @count: size of the previously mentioned array
+ * @align: parameters of the regulator step and offset
+ * @process_id: process id of the HW module
+ * @speedo_id: speedo id of the HW module
+ * @speedo_value: speedo value of the HW module
+ * @max_freq: highest safe clock rate
+ *
+ * On Tegra, a CVB table encodes the relationship between operating voltage
+ * and safe maximal frequency for a given module (e.g. GPU or CPU). This
+ * function calculates the optimal voltage-frequency operating points
+ * for the given arguments and exports them via the OPP library for the
+ * given @dev. Returns a pointer to the struct cvb_table that matched
+ * or an ERR_PTR on failure.
+ */
+const struct cvb_table *
+tegra_cvb_add_opp_table(struct device *dev, const struct cvb_table *tables,
+			size_t count, struct rail_alignment *align,
+			int process_id, int speedo_id, int speedo_value,
+			unsigned long max_freq)
+{
+	size_t i;
+	int ret;
+
+	for (i = 0; i < count; i++) {
+		const struct cvb_table *table = &tables[i];
+
+		if (table->speedo_id != -1 && table->speedo_id != speedo_id)
+			continue;
+
+		if (table->process_id != -1 && table->process_id != process_id)
+			continue;
+
+		ret = build_opp_table(dev, table, align, speedo_value,
+				      max_freq);
+		return ret ? ERR_PTR(ret) : table;
+	}
+
+	return ERR_PTR(-EINVAL);
+}
+
+void tegra_cvb_remove_opp_table(struct device *dev,
+				const struct cvb_table *table,
+				unsigned long max_freq)
+{
+	unsigned int i;
+
+	for (i = 0; i < MAX_DVFS_FREQS; i++) {
+		const struct cvb_table_freq_entry *entry = &table->entries[i];
+
+		if (!entry->freq || (entry->freq > max_freq))
+			break;
+
+		dev_pm_opp_remove(dev, entry->freq);
+	}
+}