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, 69 insertions, 0 deletions

diff --git a/fs/xfs/xfs_itable.h b/fs/xfs/xfs_itable.h
new file mode 100644
index 000000000..2d0612f14
--- /dev/null
+++ b/fs/xfs/xfs_itable.h
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2000-2001 Silicon Graphics, Inc.  All Rights Reserved.
+ */
+#ifndef __XFS_ITABLE_H__
+#define	__XFS_ITABLE_H__
+
+/* In-memory representation of a userspace request for batch inode data. */
+struct xfs_ibulk {
+	struct xfs_mount	*mp;
+	struct mnt_idmap	*idmap;
+	void __user		*ubuffer; /* user output buffer */
+	xfs_ino_t		startino; /* start with this inode */
+	unsigned int		icount;   /* number of elements in ubuffer */
+	unsigned int		ocount;   /* number of records returned */
+	unsigned int		flags;    /* XFS_IBULK_FLAG_* */
+	unsigned int		iwalk_flags; /* XFS_IWALK_FLAG_* */
+};
+
+/* Fill out the bs_extents64 field if set. */
+#define XFS_IBULK_NREXT64	(1U << 0)
+
+/* Signal that we can return metadata directories. */
+#define XFS_IBULK_METADIR	(1U << 1)
+
+/*
+ * Advance the user buffer pointer by one record of the given size.  If the
+ * buffer is now full, return the appropriate error code.
+ */
+static inline int
+xfs_ibulk_advance(
+	struct xfs_ibulk	*breq,
+	size_t			bytes)
+{
+	char __user		*b = breq->ubuffer;
+
+	breq->ubuffer = b + bytes;
+	breq->ocount++;
+	return breq->ocount == breq->icount ? -ECANCELED : 0;
+}
+
+/*
+ * Return stat information in bulk (by-inode) for the filesystem.
+ */
+
+/*
+ * Return codes for the formatter function are 0 to continue iterating, and
+ * non-zero to stop iterating.  Any non-zero value will be passed up to the
+ * bulkstat/inumbers caller.  The special value -ECANCELED can be used to stop
+ * iteration, as neither bulkstat nor inumbers will ever generate that error
+ * code on their own.
+ */
+
+typedef int (*bulkstat_one_fmt_pf)(struct xfs_ibulk *breq,
+		const struct xfs_bulkstat *bstat);
+
+int xfs_bulkstat_one(struct xfs_ibulk *breq, bulkstat_one_fmt_pf formatter);
+int xfs_bulkstat(struct xfs_ibulk *breq, bulkstat_one_fmt_pf formatter);
+void xfs_bulkstat_to_bstat(struct xfs_mount *mp, struct xfs_bstat *bs1,
+		const struct xfs_bulkstat *bstat);
+
+typedef int (*inumbers_fmt_pf)(struct xfs_ibulk *breq,
+		const struct xfs_inumbers *igrp);
+
+int xfs_inumbers(struct xfs_ibulk *breq, inumbers_fmt_pf formatter);
+void xfs_inumbers_to_inogrp(struct xfs_inogrp *ig1,
+		const struct xfs_inumbers *ig);
+
+#endif	/* __XFS_ITABLE_H__ */