[PATCH pve-qemu 2/3] build: query Hyper-V enlightenment flags for CPU flags list

[Arthur Bied-Charreton <a.bied-charreton@proxmox.com>]

The recognized CPU flags list shipped with pve-qemu-kvm must include
Hyper-V enlightenment flags so the custom CPU models API can offer them.

Query them from the 'host-x86_64-cpu' type via QMP (qom-list-properties)
in parse-cpu-flags.pl, filtering for properties with the 'hv-' prefix,
and include them in the recognized flags list.

Filter out non-boolean enlightenments, since the custom CPU model config
only supports enable/disable.

Suggested-by: Fiona Ebner <f.ebner@proxmox.com>
Signed-off-by: Arthur Bied-Charreton <a.bied-charreton@proxmox.com>
---
 debian/parse-cpu-flags.pl | 42 +++++++++++++++++++++++++++++++++++++++
 debian/rules              |  2 +-
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/debian/parse-cpu-flags.pl b/debian/parse-cpu-flags.pl
index 1847b3e..2b5d32a 100755
--- a/debian/parse-cpu-flags.pl
+++ b/debian/parse-cpu-flags.pl
@@ -2,7 +2,10 @@
 
 use warnings;
 use strict;
+use IPC::Open2;
+use JSON;
 
+my ($qemu_bin) = @ARGV;
 my @flags = ();
 my $got_flags_section;
 
@@ -20,4 +23,43 @@ while (<STDIN>) {
 
 die "no QEMU/KVM CPU flags detected from STDIN input" if scalar (@flags) <= 0;
 
+my $pid = open2(
+    my $out,
+    my $in,
+    $qemu_bin,
+    '-machine',
+    'none',
+    '-display',
+    'none',
+    '-S',
+    '-qmp',
+    'stdio',
+);
+
+sub qmp {
+    my ($cmd, %args) = @_;
+    print $in encode_json({ execute => $cmd, %args ? (arguments => \%args) : () }), "\n";
+    while (my $line = <$out>) {
+        my $msg = decode_json($line);
+        next if $msg->{event};
+        return $msg->{return} if exists $msg->{return};
+        die "QMP error: " . encode_json($msg->{error}) if $msg->{error};
+    }
+}
+
+<$out>;
+qmp('qmp_capabilities');
+my $props = qmp('qom-list-properties', typename => 'host-x86_64-cpu');
+for my $qo ($props->@*) {
+    # Filter out non-boolean flags, our custom CPU model config only supports
+    # enable/disable.
+    if (index($qo->{name}, 'hv-') == 0 && $qo->{type} eq 'bool') {
+        push @flags, $qo->{name};
+    }
+}
+qmp('quit');
+waitpid($pid, 0);
+
+@flags = sort @flags;
+
 print join("\n", @flags) or die "$!\n";
diff --git a/debian/rules b/debian/rules
index c90db29..e3eebe8 100755
--- a/debian/rules
+++ b/debian/rules
@@ -123,7 +123,7 @@ install: build
 	rm -f $(destdir)/usr/lib/kvm/virtfs-proxy-helper
 
 	# CPU flags are static for QEMU version, allows avoiding more costly checks
-	$(destdir)/usr/bin/qemu-system-x86_64 -cpu help | ./debian/parse-cpu-flags.pl > $(flagfile)
+	$(destdir)/usr/bin/qemu-system-x86_64 -cpu help | ./debian/parse-cpu-flags.pl $(destdir)/usr/bin/qemu-system-x86_64 > $(flagfile)
 
 	# Supported machine versions are static for a given QEMU binary.
 	$(destdir)/usr/bin/qemu-system-x86_64 -machine help | ./debian/parse-machines.pl > $(machine_file_x86_64)
-- 
2.47.3