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, 208 insertions, 0 deletions

diff --git a/scripts/checkstack.pl b/scripts/checkstack.pl
new file mode 100755
index 000000000..14ce31f73
--- /dev/null
+++ b/scripts/checkstack.pl
@@ -0,0 +1,208 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0
+
+#	Check the stack usage of functions
+#
+#	Copyright Joern Engel <joern@lazybastard.org>
+#	Inspired by Linus Torvalds
+#	Original idea maybe from Keith Owens
+#	s390 port and big speedup by Arnd Bergmann <arnd@bergmann-dalldorf.de>
+#	Mips port by Juan Quintela <quintela@mandrakesoft.com>
+#	Arm port by Holger Schurig
+#	Random bits by Matt Mackall <mpm@selenic.com>
+#	M68k port by Geert Uytterhoeven and Andreas Schwab
+#	AArch64, PARISC ports by Kyle McMartin
+#	sparc port by Martin Habets <errandir_news@mph.eclipse.co.uk>
+#	ppc64le port by Breno Leitao <leitao@debian.org>
+#	riscv port by Wadim Mueller <wafgo01@gmail.com>
+#	loongarch port by Youling Tang <tangyouling@kylinos.cn>
+#
+#	Usage:
+#	objdump -d vmlinux | scripts/checkstack.pl [arch] [min_stack]
+#
+#	TODO :	Port to all architectures (one regex per arch)
+
+use strict;
+
+# check for arch
+#
+# $re is used for two matches:
+# $& (whole re) matches the complete objdump line with the stack growth
+# $1 (first bracket) matches the size of the stack growth
+#
+# $dre is similar, but for dynamic stack redutions:
+# $& (whole re) matches the complete objdump line with the stack growth
+# $1 (first bracket) matches the dynamic amount of the stack growth
+#
+# $sub: subroutine for special handling to check stack usage.
+#
+# use anything else and feel the pain ;)
+my (@stack, $re, $dre, $sub, $x, $xs, $funcre, $min_stack);
+{
+	my $arch = shift;
+	if ($arch eq "") {
+		$arch = `uname -m`;
+		chomp($arch);
+	}
+
+	$min_stack = shift;
+	if ($min_stack eq "" || $min_stack !~ /^\d+$/) {
+		$min_stack = 512;
+	}
+
+	$x	= "[0-9a-f]";	# hex character
+	$xs	= "[0-9a-f ]";	# hex character or space
+	$funcre = qr/^$x* <(.*)>:$/;
+	if ($arch =~ '^(aarch|arm)64$') {
+		#ffffffc0006325cc:       a9bb7bfd        stp     x29, x30, [sp, #-80]!
+		#a110:       d11643ff        sub     sp, sp, #0x590
+		$re = qr/^.*stp.*sp, ?\#-([0-9]{1,8})\]\!/o;
+		$dre = qr/^.*sub.*sp, sp, #(0x$x{1,8})/o;
+	} elsif ($arch eq 'arm') {
+		#c0008ffc:	e24dd064	sub	sp, sp, #100	; 0x64
+		$re = qr/.*sub.*sp, sp, #([0-9]{1,4})/o;
+		$sub = \&arm_push_handling;
+	} elsif ($arch =~ /^x86(_64)?$/ || $arch =~ /^i[3456]86$/) {
+		#c0105234:       81 ec ac 05 00 00       sub    $0x5ac,%esp
+		# or
+		#    2f60:    48 81 ec e8 05 00 00       sub    $0x5e8,%rsp
+		$re = qr/^.*[as][du][db]    \$(0x$x{1,8}),\%(e|r)sp$/o;
+		$dre = qr/^.*[as][du][db]    (%.*),\%(e|r)sp$/o;
+	} elsif ($arch eq 'm68k') {
+		#    2b6c:       4e56 fb70       linkw %fp,#-1168
+		#  1df770:       defc ffe4       addaw #-28,%sp
+		$re = qr/.*(?:linkw %fp,|addaw )#-([0-9]{1,4})(?:,%sp)?$/o;
+	} elsif ($arch eq 'mips64') {
+		#8800402c:       67bdfff0        daddiu  sp,sp,-16
+		$re = qr/.*daddiu.*sp,sp,-([0-9]{1,8})/o;
+	} elsif ($arch eq 'mips') {
+		#88003254:       27bdffe0        addiu   sp,sp,-32
+		$re = qr/.*addiu.*sp,sp,-([0-9]{1,8})/o;
+	} elsif ($arch eq 'nios2') {
+		#25a8:	defffb04 	addi	sp,sp,-20
+		$re = qr/.*addi.*sp,sp,-([0-9]{1,8})/o;
+	} elsif ($arch eq 'openrisc') {
+		# c000043c:       9c 21 fe f0     l.addi r1,r1,-272
+		$re = qr/.*l\.addi.*r1,r1,-([0-9]{1,8})/o;
+	} elsif ($arch eq 'parisc' || $arch eq 'parisc64') {
+		$re = qr/.*ldo ($x{1,8})\(sp\),sp/o;
+	} elsif ($arch eq 'powerpc' || $arch =~ /^ppc(64)?(le)?$/ ) {
+		# powerpc    : 94 21 ff 30     stwu    r1,-208(r1)
+		# ppc64(le)  : 81 ff 21 f8     stdu    r1,-128(r1)
+		$re = qr/.*st[dw]u.*r1,-($x{1,8})\(r1\)/o;
+	} elsif ($arch =~ /^s390x?$/) {
+		#   11160:       a7 fb ff 60             aghi   %r15,-160
+		# or
+		#  100092:	 e3 f0 ff c8 ff 71	 lay	 %r15,-56(%r15)
+		$re = qr/.*(?:lay|ag?hi).*\%r15,-([0-9]+)(?:\(\%r15\))?$/o;
+	} elsif ($arch eq 'sparc' || $arch eq 'sparc64') {
+		# f0019d10:       9d e3 bf 90     save  %sp, -112, %sp
+		$re = qr/.*save.*%sp, -([0-9]{1,8}), %sp/o;
+	} elsif ($arch =~ /^riscv(64)?$/) {
+		#ffffffff8036e868:	c2010113          	addi	sp,sp,-992
+		$re = qr/.*addi.*sp,sp,-([0-9]{1,8})/o;
+	} elsif ($arch =~ /^loongarch(32|64)?$/) {
+		#9000000000224708:	02ff4063		addi.d  $sp, $sp, -48(0xfd0)
+		$re = qr/.*addi\..*sp, .*sp, -([0-9]{1,8}).*/o;
+	} else {
+		print("wrong or unknown architecture \"$arch\"\n");
+		exit
+	}
+}
+
+#
+# To count stack usage of push {*, fp, ip, lr, pc} instruction in ARM,
+# if FRAME POINTER is enabled.
+# e.g. c01f0d48: e92ddff0 push {r4, r5, r6, r7, r8, r9, sl, fp, ip, lr, pc}
+#
+sub arm_push_handling {
+	my $regex = qr/.*push.*fp, ip, lr, pc}/o;
+	my $size = 0;
+	my $line_arg = shift;
+
+	if ($line_arg =~ m/$regex/) {
+		$size = $line_arg =~ tr/,//;
+		$size = ($size + 1) * 4;
+	}
+
+	return $size;
+}
+
+#
+# main()
+#
+my ($func, $file, $lastslash, $total_size, $addr, $intro);
+
+$total_size = 0;
+
+while (my $line = <STDIN>) {
+	if ($line =~ m/$funcre/) {
+		$func = $1;
+		next if $line !~ m/^($x*)/;
+		if ($total_size > $min_stack) {
+			push @stack, "$intro$total_size\n";
+		}
+		$addr = "0x$1";
+		$intro = "$addr $func [$file]:";
+		my $padlen = 56 - length($intro);
+		while ($padlen > 0) {
+			$intro .= '	';
+			$padlen -= 8;
+		}
+
+		$total_size = 0;
+	}
+	elsif ($line =~ m/(.*):\s*file format/) {
+		$file = $1;
+		$file =~ s/\.ko//;
+		$lastslash = rindex($file, "/");
+		if ($lastslash != -1) {
+			$file = substr($file, $lastslash + 1);
+		}
+	}
+	elsif ($line =~ m/$re/) {
+		my $size = $1;
+		$size = hex($size) if ($size =~ /^0x/);
+
+		if ($size > 0xf0000000) {
+			$size = - $size;
+			$size += 0x80000000;
+			$size += 0x80000000;
+		}
+		next if ($size > 0x10000000);
+
+		$total_size += $size;
+	}
+	elsif (defined $dre && $line =~ m/$dre/) {
+		my $size = $1;
+
+		$size = hex($size) if ($size =~ /^0x/);
+		$total_size += $size;
+	}
+	elsif (defined $sub) {
+		my $size = &$sub($line);
+
+		$total_size += $size;
+	}
+}
+if ($total_size > $min_stack) {
+	push @stack, "$intro$total_size\n";
+}
+
+# Sort output by size (last field) and function name if size is the same
+sub sort_lines {
+	my ($a, $b) = @_;
+
+	my $num_a = $1 if $a =~ /:\t*(\d+)$/;
+	my $num_b = $1 if $b =~ /:\t*(\d+)$/;
+	my $func_a = $1 if $a =~ / (.*):/;
+	my $func_b = $1 if $b =~ / (.*):/;
+
+	if ($num_a != $num_b) {
+		return $num_b <=> $num_a;
+	} else {
+		return $func_a cmp $func_b;
+	}
+}
+
+print sort { sort_lines($a, $b) } @stack;