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, 171 insertions, 0 deletions

diff --git a/fs/ntfs/debug.c b/fs/ntfs/debug.c
new file mode 100644
index 000000000..f241ebc97
--- /dev/null
+++ b/fs/ntfs/debug.c
@@ -0,0 +1,171 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * NTFS kernel debug support.
+ *
+ * Copyright (c) 2001-2004 Anton Altaparmakov
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include "debug.h"
+
+/*
+ * __ntfs_warning - output a warning to the syslog
+ * @function:	name of function outputting the warning
+ * @sb:		super block of mounted ntfs filesystem
+ * @fmt:	warning string containing format specifications
+ * @...:	a variable number of arguments specified in @fmt
+ *
+ * Outputs a warning to the syslog for the mounted ntfs filesystem described
+ * by @sb.
+ *
+ * @fmt and the corresponding @... is printf style format string containing
+ * the warning string and the corresponding format arguments, respectively.
+ *
+ * @function is the name of the function from which __ntfs_warning is being
+ * called.
+ *
+ * Note, you should be using debug.h::ntfs_warning(@sb, @fmt, @...) instead
+ * as this provides the @function parameter automatically.
+ */
+void __ntfs_warning(const char *function, const struct super_block *sb,
+		const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+	int flen = 0;
+
+	if (function)
+		flen = strlen(function);
+	va_start(args, fmt);
+	vaf.fmt = fmt;
+	vaf.va = &args;
+#ifdef DEBUG
+	if (sb)
+		pr_warn("(device %s): %s(): %pV\n",
+			sb->s_id, flen ? function : "", &vaf);
+	else
+		pr_warn("%s(): %pV\n", flen ? function : "", &vaf);
+#else
+	if (sb)
+		pr_warn_ratelimited("(device %s): %s(): %pV\n",
+			sb->s_id, flen ? function : "", &vaf);
+	else
+		pr_warn_ratelimited("%s(): %pV\n", flen ? function : "", &vaf);
+#endif
+	va_end(args);
+}
+
+/*
+ * __ntfs_error - output an error to the syslog
+ * @function:	name of function outputting the error
+ * @sb:		super block of mounted ntfs filesystem
+ * @fmt:	error string containing format specifications
+ * @...:	a variable number of arguments specified in @fmt
+ *
+ * Outputs an error to the syslog for the mounted ntfs filesystem described
+ * by @sb.
+ *
+ * @fmt and the corresponding @... is printf style format string containing
+ * the error string and the corresponding format arguments, respectively.
+ *
+ * @function is the name of the function from which __ntfs_error is being
+ * called.
+ *
+ * Note, you should be using debug.h::ntfs_error(@sb, @fmt, @...) instead
+ * as this provides the @function parameter automatically.
+ */
+void __ntfs_error(const char *function, struct super_block *sb,
+		const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+	int flen = 0;
+
+	if (function)
+		flen = strlen(function);
+	va_start(args, fmt);
+	vaf.fmt = fmt;
+	vaf.va = &args;
+#ifdef DEBUG
+	if (sb)
+		pr_err("(device %s): %s(): %pV\n",
+		       sb->s_id, flen ? function : "", &vaf);
+	else
+		pr_err("%s(): %pV\n", flen ? function : "", &vaf);
+#else
+	if (sb)
+		pr_err_ratelimited("(device %s): %s(): %pV\n",
+		       sb->s_id, flen ? function : "", &vaf);
+	else
+		pr_err_ratelimited("%s(): %pV\n", flen ? function : "", &vaf);
+#endif
+	va_end(args);
+
+	if (sb)
+		ntfs_handle_error(sb);
+}
+
+#ifdef DEBUG
+
+/* If 1, output debug messages, and if 0, don't. */
+int debug_msgs;
+
+void __ntfs_debug(const char *file, int line, const char *function,
+		const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+	int flen = 0;
+
+	if (!debug_msgs)
+		return;
+	if (function)
+		flen = strlen(function);
+	va_start(args, fmt);
+	vaf.fmt = fmt;
+	vaf.va = &args;
+	pr_debug("(%s, %d): %s(): %pV", file, line, flen ? function : "", &vaf);
+	va_end(args);
+}
+
+/* Dump a runlist. Caller has to provide synchronisation for @rl. */
+void ntfs_debug_dump_runlist(const struct runlist_element *rl)
+{
+	int i;
+	const char *lcn_str[5] = { "LCN_DELALLOC     ", "LCN_HOLE         ",
+				   "LCN_RL_NOT_MAPPED", "LCN_ENOENT       ",
+				   "LCN_unknown      " };
+
+	if (!debug_msgs)
+		return;
+	pr_debug("Dumping runlist (values in hex):\n");
+	if (!rl) {
+		pr_debug("Run list not present.\n");
+		return;
+	}
+	pr_debug("VCN              LCN               Run length\n");
+	for (i = 0; ; i++) {
+		s64 lcn = (rl + i)->lcn;
+
+		if (lcn < 0) {
+			int index = -lcn - 1;
+
+			if (index > -LCN_ENOENT - 1)
+				index = 3;
+			pr_debug("%-16Lx %s %-16Lx%s\n",
+					(long long)(rl + i)->vcn, lcn_str[index],
+					(long long)(rl + i)->length,
+					(rl + i)->length ? "" :
+						" (runlist end)");
+		} else
+			pr_debug("%-16Lx %-16Lx  %-16Lx%s\n",
+					(long long)(rl + i)->vcn,
+					(long long)(rl + i)->lcn,
+					(long long)(rl + i)->length,
+					(rl + i)->length ? "" :
+						" (runlist end)");
+		if (!(rl + i)->length)
+			break;
+	}
+}
+
+#endif