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, 82 insertions, 0 deletions

diff --git a/ipc/compat.c b/ipc/compat.c
new file mode 100644
index 000000000..5ab822592
--- /dev/null
+++ b/ipc/compat.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 32 bit compatibility code for System V IPC
+ *
+ * Copyright (C) 1997,1998	Jakub Jelinek (jj@sunsite.mff.cuni.cz)
+ * Copyright (C) 1997		David S. Miller (davem@caip.rutgers.edu)
+ * Copyright (C) 1999		Arun Sharma <arun.sharma@intel.com>
+ * Copyright (C) 2000		VA Linux Co
+ * Copyright (C) 2000		Don Dugger <n0ano@valinux.com>
+ * Copyright (C) 2000           Hewlett-Packard Co.
+ * Copyright (C) 2000           David Mosberger-Tang <davidm@hpl.hp.com>
+ * Copyright (C) 2000           Gerhard Tonn (ton@de.ibm.com)
+ * Copyright (C) 2000-2002      Andi Kleen, SuSE Labs (x86-64 port)
+ * Copyright (C) 2000		Silicon Graphics, Inc.
+ * Copyright (C) 2001		IBM
+ * Copyright (C) 2004		IBM Deutschland Entwicklung GmbH, IBM Corporation
+ * Copyright (C) 2004		Arnd Bergmann (arnd@arndb.de)
+ *
+ * This code is collected from the versions for sparc64, mips64, s390x, ia64,
+ * ppc64 and x86_64, all of which are based on the original sparc64 version
+ * by Jakub Jelinek.
+ *
+ */
+#include <linux/compat.h>
+#include <linux/errno.h>
+#include <linux/highuid.h>
+#include <linux/init.h>
+#include <linux/msg.h>
+#include <linux/shm.h>
+#include <linux/syscalls.h>
+#include <linux/ptrace.h>
+
+#include <linux/mutex.h>
+#include <linux/uaccess.h>
+
+#include "util.h"
+
+int get_compat_ipc64_perm(struct ipc64_perm *to,
+			  struct compat_ipc64_perm __user *from)
+{
+	struct compat_ipc64_perm v;
+	if (copy_from_user(&v, from, sizeof(v)))
+		return -EFAULT;
+	to->uid = v.uid;
+	to->gid = v.gid;
+	to->mode = v.mode;
+	return 0;
+}
+
+int get_compat_ipc_perm(struct ipc64_perm *to,
+			struct compat_ipc_perm __user *from)
+{
+	struct compat_ipc_perm v;
+	if (copy_from_user(&v, from, sizeof(v)))
+		return -EFAULT;
+	to->uid = v.uid;
+	to->gid = v.gid;
+	to->mode = v.mode;
+	return 0;
+}
+
+void to_compat_ipc64_perm(struct compat_ipc64_perm *to, struct ipc64_perm *from)
+{
+	to->key = from->key;
+	to->uid = from->uid;
+	to->gid = from->gid;
+	to->cuid = from->cuid;
+	to->cgid = from->cgid;
+	to->mode = from->mode;
+	to->seq = from->seq;
+}
+
+void to_compat_ipc_perm(struct compat_ipc_perm *to, struct ipc64_perm *from)
+{
+	to->key = from->key;
+	SET_UID(to->uid, from->uid);
+	SET_GID(to->gid, from->gid);
+	SET_UID(to->cuid, from->cuid);
+	SET_GID(to->cgid, from->cgid);
+	to->mode = from->mode;
+	to->seq = from->seq;
+}