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, 335 insertions, 0 deletions

diff --git a/lib/test_sysctl.c b/lib/test_sysctl.c
new file mode 100644
index 000000000..909cfcf76
--- /dev/null
+++ b/lib/test_sysctl.c
@@ -0,0 +1,335 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR copyleft-next-0.3.1
+/*
+ * proc sysctl test driver
+ *
+ * Copyright (C) 2017 Luis R. Rodriguez <mcgrof@kernel.org>
+ */
+
+/*
+ * This module provides an interface to the proc sysctl interfaces.  This
+ * driver requires CONFIG_SYSCTL. It will not normally be loaded by the
+ * system unless explicitly requested by name. You can also build this driver
+ * into your kernel.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/async.h>
+#include <linux/delay.h>
+#include <linux/vmalloc.h>
+
+static int i_zero;
+static int i_one_hundred = 100;
+static int match_int_ok = 1;
+
+enum {
+	TEST_H_SETUP_NODE,
+	TEST_H_MNT,
+	TEST_H_MNTERROR,
+	TEST_H_EMPTY_ADD,
+	TEST_H_EMPTY,
+	TEST_H_U8,
+	TEST_H_SIZE /* Always at the end */
+};
+
+static struct ctl_table_header *ctl_headers[TEST_H_SIZE] = {};
+struct test_sysctl_data {
+	int int_0001;
+	int int_0002;
+	int int_0003[4];
+
+	int boot_int;
+
+	unsigned int uint_0001;
+
+	char string_0001[65];
+
+#define SYSCTL_TEST_BITMAP_SIZE	65536
+	unsigned long *bitmap_0001;
+};
+
+static struct test_sysctl_data test_data = {
+	.int_0001 = 60,
+	.int_0002 = 1,
+
+	.int_0003[0] = 0,
+	.int_0003[1] = 1,
+	.int_0003[2] = 2,
+	.int_0003[3] = 3,
+
+	.boot_int = 0,
+
+	.uint_0001 = 314,
+
+	.string_0001 = "(none)",
+};
+
+/* These are all under /proc/sys/debug/test_sysctl/ */
+static const struct ctl_table test_table[] = {
+	{
+		.procname	= "int_0001",
+		.data		= &test_data.int_0001,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &i_zero,
+		.extra2         = &i_one_hundred,
+	},
+	{
+		.procname	= "int_0002",
+		.data		= &test_data.int_0002,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "int_0003",
+		.data		= &test_data.int_0003,
+		.maxlen		= sizeof(test_data.int_0003),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "match_int",
+		.data		= &match_int_ok,
+		.maxlen		= sizeof(match_int_ok),
+		.mode		= 0444,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "boot_int",
+		.data		= &test_data.boot_int,
+		.maxlen		= sizeof(test_data.boot_int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+		.extra1		= SYSCTL_ZERO,
+		.extra2         = SYSCTL_ONE,
+	},
+	{
+		.procname	= "uint_0001",
+		.data		= &test_data.uint_0001,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_douintvec,
+	},
+	{
+		.procname	= "string_0001",
+		.data		= &test_data.string_0001,
+		.maxlen		= sizeof(test_data.string_0001),
+		.mode		= 0644,
+		.proc_handler	= proc_dostring,
+	},
+	{
+		.procname	= "bitmap_0001",
+		.data		= &test_data.bitmap_0001,
+		.maxlen		= SYSCTL_TEST_BITMAP_SIZE,
+		.mode		= 0644,
+		.proc_handler	= proc_do_large_bitmap,
+	},
+};
+
+static void test_sysctl_calc_match_int_ok(void)
+{
+	int i;
+
+	struct {
+		int defined;
+		int wanted;
+	} match_int[] = {
+		{.defined = *(int *)SYSCTL_ZERO,	.wanted = 0},
+		{.defined = *(int *)SYSCTL_ONE,		.wanted = 1},
+		{.defined = *(int *)SYSCTL_TWO,		.wanted = 2},
+		{.defined = *(int *)SYSCTL_THREE,	.wanted = 3},
+		{.defined = *(int *)SYSCTL_FOUR,	.wanted = 4},
+		{.defined = *(int *)SYSCTL_ONE_HUNDRED, .wanted = 100},
+		{.defined = *(int *)SYSCTL_TWO_HUNDRED,	.wanted = 200},
+		{.defined = *(int *)SYSCTL_ONE_THOUSAND, .wanted = 1000},
+		{.defined = *(int *)SYSCTL_THREE_THOUSAND, .wanted = 3000},
+		{.defined = *(int *)SYSCTL_INT_MAX,	.wanted = INT_MAX},
+		{.defined = *(int *)SYSCTL_MAXOLDUID,	.wanted = 65535},
+		{.defined = *(int *)SYSCTL_NEG_ONE,	.wanted = -1},
+	};
+
+	for (i = 0; i < ARRAY_SIZE(match_int); i++)
+		if (match_int[i].defined != match_int[i].wanted)
+			match_int_ok = 0;
+}
+
+static int test_sysctl_setup_node_tests(void)
+{
+	test_sysctl_calc_match_int_ok();
+	test_data.bitmap_0001 = kzalloc(SYSCTL_TEST_BITMAP_SIZE/8, GFP_KERNEL);
+	if (!test_data.bitmap_0001)
+		return -ENOMEM;
+	ctl_headers[TEST_H_SETUP_NODE] = register_sysctl("debug/test_sysctl", test_table);
+	if (!ctl_headers[TEST_H_SETUP_NODE]) {
+		kfree(test_data.bitmap_0001);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+/* Used to test that unregister actually removes the directory */
+static const struct ctl_table test_table_unregister[] = {
+	{
+		.procname	= "unregister_error",
+		.data		= &test_data.int_0001,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+	},
+};
+
+static int test_sysctl_run_unregister_nested(void)
+{
+	struct ctl_table_header *unregister;
+
+	unregister = register_sysctl("debug/test_sysctl/unregister_error",
+				   test_table_unregister);
+	if (!unregister)
+		return -ENOMEM;
+
+	unregister_sysctl_table(unregister);
+	return 0;
+}
+
+static int test_sysctl_run_register_mount_point(void)
+{
+	ctl_headers[TEST_H_MNT]
+		= register_sysctl_mount_point("debug/test_sysctl/mnt");
+	if (!ctl_headers[TEST_H_MNT])
+		return -ENOMEM;
+
+	ctl_headers[TEST_H_MNTERROR]
+		= register_sysctl("debug/test_sysctl/mnt/mnt_error",
+				  test_table_unregister);
+	/*
+	 * Don't check the result.:
+	 * If it fails (expected behavior), return 0.
+	 * If successful (missbehavior of register mount point), we want to see
+	 * mnt_error when we run the sysctl test script
+	 */
+
+	return 0;
+}
+
+static const struct ctl_table test_table_empty[] = { };
+
+static int test_sysctl_run_register_empty(void)
+{
+	/* Tets that an empty dir can be created */
+	ctl_headers[TEST_H_EMPTY_ADD]
+		= register_sysctl("debug/test_sysctl/empty_add", test_table_empty);
+	if (!ctl_headers[TEST_H_EMPTY_ADD])
+		return -ENOMEM;
+
+	/* Test that register on top of an empty dir works */
+	ctl_headers[TEST_H_EMPTY]
+		= register_sysctl("debug/test_sysctl/empty_add/empty", test_table_empty);
+	if (!ctl_headers[TEST_H_EMPTY])
+		return -ENOMEM;
+
+	return 0;
+}
+
+static const struct ctl_table table_u8_over[] = {
+	{
+		.procname	= "u8_over",
+		.data		= &test_data.uint_0001,
+		.maxlen		= sizeof(u8),
+		.mode		= 0644,
+		.proc_handler	= proc_dou8vec_minmax,
+		.extra1		= SYSCTL_FOUR,
+		.extra2		= SYSCTL_ONE_THOUSAND,
+	},
+};
+
+static const struct ctl_table table_u8_under[] = {
+	{
+		.procname	= "u8_under",
+		.data		= &test_data.uint_0001,
+		.maxlen		= sizeof(u8),
+		.mode		= 0644,
+		.proc_handler	= proc_dou8vec_minmax,
+		.extra1		= SYSCTL_NEG_ONE,
+		.extra2		= SYSCTL_ONE_HUNDRED,
+	},
+};
+
+static const struct ctl_table table_u8_valid[] = {
+	{
+		.procname	= "u8_valid",
+		.data		= &test_data.uint_0001,
+		.maxlen		= sizeof(u8),
+		.mode		= 0644,
+		.proc_handler	= proc_dou8vec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_TWO_HUNDRED,
+	},
+};
+
+static int test_sysctl_register_u8_extra(void)
+{
+	/* should fail because it's over */
+	ctl_headers[TEST_H_U8]
+		= register_sysctl("debug/test_sysctl", table_u8_over);
+	if (ctl_headers[TEST_H_U8])
+		return -ENOMEM;
+
+	/* should fail because it's under */
+	ctl_headers[TEST_H_U8]
+		= register_sysctl("debug/test_sysctl", table_u8_under);
+	if (ctl_headers[TEST_H_U8])
+		return -ENOMEM;
+
+	/* should not fail because it's valid */
+	ctl_headers[TEST_H_U8]
+		= register_sysctl("debug/test_sysctl", table_u8_valid);
+	if (!ctl_headers[TEST_H_U8])
+		return -ENOMEM;
+
+	return 0;
+}
+
+static int __init test_sysctl_init(void)
+{
+	int err = 0;
+
+	int (*func_array[])(void) = {
+		test_sysctl_setup_node_tests,
+		test_sysctl_run_unregister_nested,
+		test_sysctl_run_register_mount_point,
+		test_sysctl_run_register_empty,
+		test_sysctl_register_u8_extra
+	};
+
+	for (int i = 0; !err && i < ARRAY_SIZE(func_array); i++)
+		err = func_array[i]();
+
+	return err;
+}
+module_init(test_sysctl_init);
+
+static void __exit test_sysctl_exit(void)
+{
+	kfree(test_data.bitmap_0001);
+	for (int i = 0; i < TEST_H_SIZE; i++) {
+		if (ctl_headers[i])
+			unregister_sysctl_table(ctl_headers[i]);
+	}
+}
+
+module_exit(test_sysctl_exit);
+
+MODULE_AUTHOR("Luis R. Rodriguez <mcgrof@kernel.org>");
+MODULE_DESCRIPTION("proc sysctl test driver");
+MODULE_LICENSE("GPL");