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, 53 insertions, 0 deletions

diff --git a/scripts/checkdeclares.pl b/scripts/checkdeclares.pl
new file mode 100755
index 000000000..f6d551c84
--- /dev/null
+++ b/scripts/checkdeclares.pl
@@ -0,0 +1,53 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0
+#
+# checkdeclares: find struct declared more than once
+#
+# Copyright 2021 Wan Jiabing<wanjiabing@vivo.com>
+# Inspired by checkincludes.pl
+#
+# This script checks for duplicate struct declares.
+# Note that this will not take into consideration macros so
+# you should run this only if you know you do have real dups
+# and do not have them under #ifdef's.
+# You could also just review the results.
+
+use strict;
+
+sub usage {
+	print "Usage: checkdeclares.pl file1.h ...\n";
+	print "Warns of struct declaration duplicates\n";
+	exit 1;
+}
+
+if ($#ARGV < 0) {
+	usage();
+}
+
+my $dup_counter = 0;
+
+foreach my $file (@ARGV) {
+	open(my $f, '<', $file)
+	    or die "Cannot open $file: $!.\n";
+
+	my %declaredstructs = ();
+
+	while (<$f>) {
+		if (m/^\s*struct\s*(\w*);$/o) {
+			++$declaredstructs{$1};
+		}
+	}
+
+	close($f);
+
+	foreach my $structname (keys %declaredstructs) {
+		if ($declaredstructs{$structname} > 1) {
+			print "$file: struct $structname is declared more than once.\n";
+			++$dup_counter;
+		}
+	}
+}
+
+if ($dup_counter == 0) {
+	print "No duplicate struct declares found.\n";
+}