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, 91 insertions, 0 deletions

diff --git a/drivers/edac/debugfs.c b/drivers/edac/debugfs.c
new file mode 100644
index 000000000..447d0c620
--- /dev/null
+++ b/drivers/edac/debugfs.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include "edac_module.h"
+
+static struct dentry *edac_debugfs;
+
+void __init edac_debugfs_init(void)
+{
+	edac_debugfs = debugfs_create_dir("edac", NULL);
+}
+
+void edac_debugfs_exit(void)
+{
+	debugfs_remove_recursive(edac_debugfs);
+}
+
+void edac_create_debugfs_nodes(struct mem_ctl_info *mci)
+{
+	mci->debugfs = debugfs_create_dir(mci->dev.kobj.name, edac_debugfs);
+}
+
+/* Create a toplevel dir under EDAC's debugfs hierarchy */
+struct dentry *edac_debugfs_create_dir(const char *dirname)
+{
+	if (!edac_debugfs)
+		return NULL;
+
+	return debugfs_create_dir(dirname, edac_debugfs);
+}
+EXPORT_SYMBOL_GPL(edac_debugfs_create_dir);
+
+/* Create a toplevel dir under EDAC's debugfs hierarchy with parent @parent */
+struct dentry *
+edac_debugfs_create_dir_at(const char *dirname, struct dentry *parent)
+{
+	return debugfs_create_dir(dirname, parent);
+}
+EXPORT_SYMBOL_GPL(edac_debugfs_create_dir_at);
+
+/*
+ * Create a file under EDAC's hierarchy or a sub-hierarchy:
+ *
+ * @name: file name
+ * @mode: file permissions
+ * @parent: parent dentry. If NULL, it becomes the toplevel EDAC dir
+ * @data: private data of caller
+ * @fops: file operations of this file
+ */
+struct dentry *
+edac_debugfs_create_file(const char *name, umode_t mode, struct dentry *parent,
+			 void *data, const struct file_operations *fops)
+{
+	if (!parent)
+		parent = edac_debugfs;
+
+	return debugfs_create_file(name, mode, parent, data, fops);
+}
+EXPORT_SYMBOL_GPL(edac_debugfs_create_file);
+
+/* Wrapper for debugfs_create_x8() */
+void edac_debugfs_create_x8(const char *name, umode_t mode,
+			    struct dentry *parent, u8 *value)
+{
+	if (!parent)
+		parent = edac_debugfs;
+
+	debugfs_create_x8(name, mode, parent, value);
+}
+EXPORT_SYMBOL_GPL(edac_debugfs_create_x8);
+
+/* Wrapper for debugfs_create_x16() */
+void edac_debugfs_create_x16(const char *name, umode_t mode,
+			     struct dentry *parent, u16 *value)
+{
+	if (!parent)
+		parent = edac_debugfs;
+
+	debugfs_create_x16(name, mode, parent, value);
+}
+EXPORT_SYMBOL_GPL(edac_debugfs_create_x16);
+
+/* Wrapper for debugfs_create_x32() */
+void edac_debugfs_create_x32(const char *name, umode_t mode,
+			     struct dentry *parent, u32 *value)
+{
+	if (!parent)
+		parent = edac_debugfs;
+
+	debugfs_create_x32(name, mode, parent, value);
+}
+EXPORT_SYMBOL_GPL(edac_debugfs_create_x32);