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, 29 insertions, 0 deletions

diff --git a/arch/powerpc/boot/cuboot.c b/arch/powerpc/boot/cuboot.c
new file mode 100644
index 000000000..7f186658f
--- /dev/null
+++ b/arch/powerpc/boot/cuboot.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Compatibility for old (not device tree aware) U-Boot versions
+ *
+ * Author: Scott Wood <scottwood@freescale.com>
+ * Consolidated using macros by David Gibson <david@gibson.dropbear.id.au>
+ *
+ * Copyright 2007 David Gibson, IBM Corporation.
+ * Copyright (c) 2007 Freescale Semiconductor, Inc.
+ */
+
+#include "ops.h"
+#include "stdio.h"
+
+#include "ppcboot.h"
+
+void cuboot_init(unsigned long r4, unsigned long r5,
+		 unsigned long r6, unsigned long r7,
+		 unsigned long end_of_ram)
+{
+	unsigned long avail_ram = end_of_ram - (unsigned long)_end;
+
+	loader_info.initrd_addr = r4;
+	loader_info.initrd_size = r4 ? r5 - r4 : 0;
+	loader_info.cmdline = (char *)r6;
+	loader_info.cmdline_len = r7 - r6;
+
+	simple_alloc_init(_end, avail_ram - 1024*1024, 32, 64);
+}