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/fs/jfs/jfs_debug.c b/fs/jfs/jfs_debug.c
new file mode 100644
index 000000000..44b62b3c3
--- /dev/null
+++ b/fs/jfs/jfs_debug.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *   Copyright (C) International Business Machines Corp., 2000-2004
+ *   Portions Copyright (C) Christoph Hellwig, 2001-2002
+ */
+
+#include <linux/fs.h>
+#include <linux/ctype.h>
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/uaccess.h>
+#include "jfs_incore.h"
+#include "jfs_filsys.h"
+#include "jfs_debug.h"
+
+#ifdef PROC_FS_JFS /* see jfs_debug.h */
+
+#ifdef CONFIG_JFS_DEBUG
+static int jfs_loglevel_proc_show(struct seq_file *m, void *v)
+{
+	seq_printf(m, "%d\n", jfsloglevel);
+	return 0;
+}
+
+static int jfs_loglevel_proc_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, jfs_loglevel_proc_show, NULL);
+}
+
+static ssize_t jfs_loglevel_proc_write(struct file *file,
+		const char __user *buffer, size_t count, loff_t *ppos)
+{
+	char c;
+
+	if (get_user(c, buffer))
+		return -EFAULT;
+
+	/* yes, I know this is an ASCIIism.  --hch */
+	if (c < '0' || c > '9')
+		return -EINVAL;
+	jfsloglevel = c - '0';
+	return count;
+}
+
+static const struct proc_ops jfs_loglevel_proc_ops = {
+	.proc_open	= jfs_loglevel_proc_open,
+	.proc_read	= seq_read,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= single_release,
+	.proc_write	= jfs_loglevel_proc_write,
+};
+#endif
+
+void jfs_proc_init(void)
+{
+	struct proc_dir_entry *base;
+
+	base = proc_mkdir("fs/jfs", NULL);
+	if (!base)
+		return;
+
+#ifdef CONFIG_JFS_STATISTICS
+	proc_create_single("lmstats", 0, base, jfs_lmstats_proc_show);
+	proc_create_single("txstats", 0, base, jfs_txstats_proc_show);
+	proc_create_single("xtstat", 0, base, jfs_xtstat_proc_show);
+	proc_create_single("mpstat", 0, base, jfs_mpstat_proc_show);
+#endif
+#ifdef CONFIG_JFS_DEBUG
+	proc_create_single("TxAnchor", 0, base, jfs_txanchor_proc_show);
+	proc_create("loglevel", 0, base, &jfs_loglevel_proc_ops);
+#endif
+}
+
+void jfs_proc_clean(void)
+{
+	remove_proc_subtree("fs/jfs", NULL);
+}
+
+#endif /* PROC_FS_JFS */