KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 260 insertions, 0 deletions

diff --git a/scripts/cleanpatch b/scripts/cleanpatch
new file mode 100755
index 000000000..9f1755271
--- /dev/null
+++ b/scripts/cleanpatch
@@ -0,0 +1,260 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0
+#
+# Clean a patch file -- or directory of patch files -- of stealth whitespace.
+# WARNING: this can be a highly destructive operation.  Use with caution.
+#
+
+use warnings;
+use bytes;
+use File::Basename;
+
+# Default options
+$max_width = 79;
+
+# Clean up space-tab sequences, either by removing spaces or
+# replacing them with tabs.
+sub clean_space_tabs($)
+{
+    no bytes;			# Tab alignment depends on characters
+
+    my($li) = @_;
+    my($lo) = '';
+    my $pos = 0;
+    my $nsp = 0;
+    my($i, $c);
+
+    for ($i = 0; $i < length($li); $i++) {
+	$c = substr($li, $i, 1);
+	if ($c eq "\t") {
+	    my $npos = ($pos+$nsp+8) & ~7;
+	    my $ntab = ($npos >> 3) - ($pos >> 3);
+	    $lo .= "\t" x $ntab;
+	    $pos = $npos;
+	    $nsp = 0;
+	} elsif ($c eq "\n" || $c eq "\r") {
+	    $lo .= " " x $nsp;
+	    $pos += $nsp;
+	    $nsp = 0;
+	    $lo .= $c;
+	    $pos = 0;
+	} elsif ($c eq " ") {
+	    $nsp++;
+	} else {
+	    $lo .= " " x $nsp;
+	    $pos += $nsp;
+	    $nsp = 0;
+	    $lo .= $c;
+	    $pos++;
+	}
+    }
+    $lo .= " " x $nsp;
+    return $lo;
+}
+
+# Compute the visual width of a string
+sub strwidth($) {
+    no bytes;			# Tab alignment depends on characters
+
+    my($li) = @_;
+    my($c, $i);
+    my $pos = 0;
+    my $mlen = 0;
+
+    for ($i = 0; $i < length($li); $i++) {
+	$c = substr($li,$i,1);
+	if ($c eq "\t") {
+	    $pos = ($pos+8) & ~7;
+	} elsif ($c eq "\n") {
+	    $mlen = $pos if ($pos > $mlen);
+	    $pos = 0;
+	} else {
+	    $pos++;
+	}
+    }
+
+    $mlen = $pos if ($pos > $mlen);
+    return $mlen;
+}
+
+$name = basename($0);
+
+@files = ();
+
+while (defined($a = shift(@ARGV))) {
+    if ($a =~ /^-/) {
+	if ($a eq '-width' || $a eq '-w') {
+	    $max_width = shift(@ARGV)+0;
+	} else {
+	    print STDERR "Usage: $name [-width #] files...\n";
+	    exit 1;
+	}
+    } else {
+	push(@files, $a);
+    }
+}
+
+foreach $f ( @files ) {
+    print STDERR "$name: $f\n";
+
+    if (! -f $f) {
+	print STDERR "$f: not a file\n";
+	next;
+    }
+
+    if (!open(FILE, '+<', $f)) {
+	print STDERR "$name: Cannot open file: $f: $!\n";
+	next;
+    }
+
+    binmode FILE;
+
+    # First, verify that it is not a binary file; consider any file
+    # with a zero byte to be a binary file.  Is there any better, or
+    # additional, heuristic that should be applied?
+    $is_binary = 0;
+
+    while (read(FILE, $data, 65536) > 0) {
+	if ($data =~ /\0/) {
+	    $is_binary = 1;
+	    last;
+	}
+    }
+
+    if ($is_binary) {
+	print STDERR "$name: $f: binary file\n";
+	next;
+    }
+
+    seek(FILE, 0, 0);
+
+    $in_bytes = 0;
+    $out_bytes = 0;
+    $lineno = 0;
+
+    @lines  = ();
+
+    $in_hunk = 0;
+    $err = 0;
+
+    while ( defined($line = <FILE>) ) {
+	$lineno++;
+	$in_bytes += length($line);
+
+	if (!$in_hunk) {
+	    if ($line =~
+		/^\@\@\s+\-([0-9]+),([0-9]+)\s+\+([0-9]+),([0-9]+)\s\@\@/) {
+		$minus_lines = $2;
+		$plus_lines = $4;
+		if ($minus_lines || $plus_lines) {
+		    $in_hunk = 1;
+		    @hunk_lines = ($line);
+		}
+	    } else {
+		push(@lines, $line);
+		$out_bytes += length($line);
+	    }
+	} else {
+	    # We're in a hunk
+
+	    if ($line =~ /^\+/) {
+		$plus_lines--;
+
+		$text = substr($line, 1);
+		$text =~ s/[ \t\r]*$//;		# Remove trailing spaces
+		$text = clean_space_tabs($text);
+
+		$l_width = strwidth($text);
+		if ($max_width && $l_width > $max_width) {
+		    print STDERR
+			"$f:$lineno: adds line exceeds $max_width ",
+			"characters ($l_width)\n";
+		}
+
+		push(@hunk_lines, '+'.$text);
+	    } elsif ($line =~ /^\-/) {
+		$minus_lines--;
+		push(@hunk_lines, $line);
+	    } elsif ($line =~ /^ /) {
+		$plus_lines--;
+		$minus_lines--;
+		push(@hunk_lines, $line);
+	    } else {
+		print STDERR "$name: $f: malformed patch\n";
+		$err = 1;
+		last;
+	    }
+
+	    if ($plus_lines < 0 || $minus_lines < 0) {
+		print STDERR "$name: $f: malformed patch\n";
+		$err = 1;
+		last;
+	    } elsif ($plus_lines == 0 && $minus_lines == 0) {
+		# End of a hunk.  Process this hunk.
+		my $i;
+		my $l;
+		my @h = ();
+		my $adj = 0;
+		my $done = 0;
+
+		for ($i = scalar(@hunk_lines)-1; $i > 0; $i--) {
+		    $l = $hunk_lines[$i];
+		    if (!$done && $l eq "+\n") {
+			$adj++; # Skip this line
+		    } elsif ($l =~ /^[ +]/) {
+			$done = 1;
+			unshift(@h, $l);
+		    } else {
+			unshift(@h, $l);
+		    }
+		}
+
+		$l = $hunk_lines[0];  # Hunk header
+		undef @hunk_lines;    # Free memory
+
+		if ($adj) {
+		    die unless
+			($l =~ /^\@\@\s+\-([0-9]+),([0-9]+)\s+\+([0-9]+),([0-9]+)\s\@\@(.*)$/);
+		    my $mstart = $1;
+		    my $mlin = $2;
+		    my $pstart = $3;
+		    my $plin = $4;
+		    my $tail = $5; # doesn't include the final newline
+
+		    $l = sprintf("@@ -%d,%d +%d,%d @@%s\n",
+				 $mstart, $mlin, $pstart, $plin-$adj,
+				 $tail);
+		}
+		unshift(@h, $l);
+
+		# Transfer to the output array
+		foreach $l (@h) {
+		    $out_bytes += length($l);
+		    push(@lines, $l);
+		}
+
+		$in_hunk = 0;
+	    }
+	}
+    }
+
+    if ($in_hunk) {
+	print STDERR "$name: $f: malformed patch\n";
+	$err = 1;
+    }
+
+    if (!$err) {
+	if ($in_bytes != $out_bytes) {
+	    # Only write to the file if changed
+	    seek(FILE, 0, 0);
+	    print FILE @lines;
+
+	    if ( !defined($where = tell(FILE)) ||
+		 !truncate(FILE, $where) ) {
+		die "$name: Failed to truncate modified file: $f: $!\n";
+	    }
+	}
+    }
+
+    close(FILE);
+}