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, 205 insertions, 0 deletions

diff --git a/lib/tests/bitops_kunit.c b/lib/tests/bitops_kunit.c
new file mode 100644
index 000000000..7fd9d697f
--- /dev/null
+++ b/lib/tests/bitops_kunit.c
@@ -0,0 +1,205 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 Intel Corporation
+ * Copyright (C) 2026 Ryota Sakamoto <sakamo.ryota@gmail.com>
+ */
+
+#include <linux/bitops.h>
+#include <linux/module.h>
+#include <kunit/test.h>
+
+/* use an enum because that's the most common BITMAP usage */
+enum bitops_fun {
+	BITOPS_4 = 4,
+	BITOPS_7 = 7,
+	BITOPS_11 = 11,
+	BITOPS_31 = 31,
+	BITOPS_88 = 88,
+	BITOPS_LENGTH = 256
+};
+
+struct bitops_test_case {
+	const char *str;
+	const long nr;
+};
+
+static struct bitops_test_case bitops_cases[] = {
+	{
+		.str = "BITOPS_4",
+		.nr = BITOPS_4,
+	},
+	{
+		.str = "BITOPS_7",
+		.nr = BITOPS_7,
+	},
+	{
+		.str = "BITOPS_11",
+		.nr = BITOPS_11,
+	},
+	{
+		.str = "BITOPS_31",
+		.nr = BITOPS_31,
+	},
+	{
+		.str = "BITOPS_88",
+		.nr = BITOPS_88,
+	},
+};
+
+KUNIT_ARRAY_PARAM_DESC(bitops, bitops_cases, str);
+
+static void test_set_bit_clear_bit(struct kunit *test)
+{
+	const struct bitops_test_case *params = test->param_value;
+	DECLARE_BITMAP(bitmap, BITOPS_LENGTH);
+	int bit_set;
+
+	bitmap_zero(bitmap, BITOPS_LENGTH);
+
+	set_bit(params->nr, bitmap);
+	KUNIT_EXPECT_TRUE(test, test_bit(params->nr, bitmap));
+
+	clear_bit(params->nr, bitmap);
+	KUNIT_EXPECT_FALSE(test, test_bit(params->nr, bitmap));
+
+	bit_set = find_first_bit(bitmap, BITOPS_LENGTH);
+	KUNIT_EXPECT_EQ(test, bit_set, BITOPS_LENGTH);
+}
+
+static void test_change_bit(struct kunit *test)
+{
+	const struct bitops_test_case *params = test->param_value;
+	DECLARE_BITMAP(bitmap, BITOPS_LENGTH);
+	int bit_set;
+
+	bitmap_zero(bitmap, BITOPS_LENGTH);
+
+	change_bit(params->nr, bitmap);
+	KUNIT_EXPECT_TRUE(test, test_bit(params->nr, bitmap));
+
+	change_bit(params->nr, bitmap);
+	KUNIT_EXPECT_FALSE(test, test_bit(params->nr, bitmap));
+
+	bit_set = find_first_bit(bitmap, BITOPS_LENGTH);
+	KUNIT_EXPECT_EQ(test, bit_set, BITOPS_LENGTH);
+}
+
+static void test_test_and_set_bit_test_and_clear_bit(struct kunit *test)
+{
+	const struct bitops_test_case *params = test->param_value;
+	DECLARE_BITMAP(bitmap, BITOPS_LENGTH);
+	int bit_set;
+
+	bitmap_zero(bitmap, BITOPS_LENGTH);
+
+	KUNIT_EXPECT_FALSE(test, test_and_set_bit(params->nr, bitmap));
+	KUNIT_EXPECT_TRUE(test, test_bit(params->nr, bitmap));
+
+	KUNIT_EXPECT_TRUE(test, test_and_set_bit(params->nr, bitmap));
+	KUNIT_EXPECT_TRUE(test, test_bit(params->nr, bitmap));
+
+	KUNIT_EXPECT_TRUE(test, test_and_clear_bit(params->nr, bitmap));
+	KUNIT_EXPECT_FALSE(test, test_bit(params->nr, bitmap));
+
+	KUNIT_EXPECT_FALSE(test, test_and_clear_bit(params->nr, bitmap));
+	KUNIT_EXPECT_FALSE(test, test_bit(params->nr, bitmap));
+
+	bit_set = find_first_bit(bitmap, BITOPS_LENGTH);
+	KUNIT_EXPECT_EQ(test, bit_set, BITOPS_LENGTH);
+}
+
+static void test_test_and_change_bit(struct kunit *test)
+{
+	const struct bitops_test_case *params = test->param_value;
+	DECLARE_BITMAP(bitmap, BITOPS_LENGTH);
+	int bit_set;
+
+	bitmap_zero(bitmap, BITOPS_LENGTH);
+
+	KUNIT_EXPECT_FALSE(test, test_and_change_bit(params->nr, bitmap));
+	KUNIT_EXPECT_TRUE(test, test_bit(params->nr, bitmap));
+
+	KUNIT_EXPECT_TRUE(test, test_and_change_bit(params->nr, bitmap));
+	KUNIT_EXPECT_FALSE(test, test_bit(params->nr, bitmap));
+
+	bit_set = find_first_bit(bitmap, BITOPS_LENGTH);
+	KUNIT_EXPECT_EQ(test, bit_set, BITOPS_LENGTH);
+}
+
+struct order_test_case {
+	const char *str;
+	const unsigned int count;
+	const int expected;
+};
+
+static struct order_test_case order_test_cases[] = {
+	{"0x00000003", 0x00000003,  2},
+	{"0x00000004", 0x00000004,  2},
+	{"0x00001fff", 0x00001fff, 13},
+	{"0x00002000", 0x00002000, 13},
+	{"0x50000000", 0x50000000, 31},
+	{"0x80000000", 0x80000000, 31},
+	{"0x80003000", 0x80003000, 32},
+};
+
+KUNIT_ARRAY_PARAM_DESC(order, order_test_cases, str);
+
+static void test_get_count_order(struct kunit *test)
+{
+	const struct order_test_case *params = test->param_value;
+
+	KUNIT_EXPECT_EQ(test, get_count_order(params->count), params->expected);
+	KUNIT_EXPECT_EQ(test, get_count_order_long(params->count), params->expected);
+}
+
+#ifdef CONFIG_64BIT
+struct order_long_test_case {
+	const char *str;
+	const unsigned long count;
+	const int expected;
+};
+
+static struct order_long_test_case order_long_test_cases[] = {
+	{"0x0000000300000000", 0x0000000300000000, 34},
+	{"0x0000000400000000", 0x0000000400000000, 34},
+	{"0x00001fff00000000", 0x00001fff00000000, 45},
+	{"0x0000200000000000", 0x0000200000000000, 45},
+	{"0x5000000000000000", 0x5000000000000000, 63},
+	{"0x8000000000000000", 0x8000000000000000, 63},
+	{"0x8000300000000000", 0x8000300000000000, 64},
+};
+
+KUNIT_ARRAY_PARAM_DESC(order_long, order_long_test_cases, str);
+
+static void test_get_count_order_long(struct kunit *test)
+{
+	const struct order_long_test_case *params = test->param_value;
+
+	KUNIT_EXPECT_EQ(test, get_count_order_long(params->count), params->expected);
+}
+#endif
+
+static struct kunit_case bitops_test_cases[] = {
+	KUNIT_CASE_PARAM(test_set_bit_clear_bit, bitops_gen_params),
+	KUNIT_CASE_PARAM(test_change_bit, bitops_gen_params),
+	KUNIT_CASE_PARAM(test_test_and_set_bit_test_and_clear_bit, bitops_gen_params),
+	KUNIT_CASE_PARAM(test_test_and_change_bit, bitops_gen_params),
+	KUNIT_CASE_PARAM(test_get_count_order, order_gen_params),
+#ifdef CONFIG_64BIT
+	KUNIT_CASE_PARAM(test_get_count_order_long, order_long_gen_params),
+#endif
+	{},
+};
+
+static struct kunit_suite bitops_test_suite = {
+	.name = "bitops",
+	.test_cases = bitops_test_cases,
+};
+
+kunit_test_suite(bitops_test_suite);
+
+MODULE_AUTHOR("Jesse Brandeburg <jesse.brandeburg@intel.com>");
+MODULE_AUTHOR("Wei Yang <richard.weiyang@gmail.com>");
+MODULE_AUTHOR("Ryota Sakamoto <sakamo.ryota@gmail.com>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Bit testing module");