From 12e1d472e3d8e7f301f05fd7d8fb13f424f40737 Mon Sep 17 00:00:00 2001
From: Dominik Csapak <d.csapak@proxmox.com>
Date: Wed, 27 Oct 2021 13:35:27 +0200
Subject: [PATCH] drives: expose 'readonly' flag of qemu for scsi/virtio

this allows a user to set a drive to 'read-only'. This can be useful
if a disk should not be written to, or if the backing file/source is
not writable (like a mapped pbs backup to /dev/loopX).

the option is named 'ro', to achieve consistency with containers

while this could also be achieved by setting 'snapshot=1', this would
create a temporary file in /var/tmp which can get quite big.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 PVE/QemuServer.pm       |  6 ++++++
 PVE/QemuServer/Drive.pm | 11 +++++++++++
 2 files changed, 17 insertions(+)

diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index 6ee7b556..ba6308cf 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -1597,6 +1597,12 @@ sub print_drive_commandline_full {
 	$opts .= ",snapshot=$v";
     }
 
+    # ro is 'readonly', and only accepts on|off
+    if (defined($drive->{ro})) {
+	my $v = $drive->{ro} ? 'on' : 'off';
+	$opts .= ",readonly=$v";
+    }
+
     foreach my $type (['', '-total'], [_rd => '-read'], [_wr => '-write']) {
 	my ($dir, $qmpname) = @$type;
 	if (my $v = $drive->{"mbps$dir"}) {
diff --git a/PVE/QemuServer/Drive.pm b/PVE/QemuServer/Drive.pm
index ff184343..97b82f9c 100644
--- a/PVE/QemuServer/Drive.pm
+++ b/PVE/QemuServer/Drive.pm
@@ -175,6 +175,14 @@ my %queues_fmt = (
     }
 );
 
+my %readonly_fmt = (
+    ro => {
+	type => 'boolean',
+	description => "Whether the drive is read-only.",
+	optional => 1,
+    },
+);
+
 my %scsiblock_fmt = (
     scsiblock => {
 	type => 'boolean',
@@ -269,6 +277,7 @@ my $scsi_fmt = {
     %drivedesc_base,
     %iothread_fmt,
     %queues_fmt,
+    %readonly_fmt,
     %scsiblock_fmt,
     %ssd_fmt,
     %wwn_fmt,
@@ -297,6 +306,7 @@ PVE::JSONSchema::register_standard_option("pve-qm-sata", $satadesc);
 my $virtio_fmt = {
     %drivedesc_base,
     %iothread_fmt,
+    %readonly_fmt,
 };
 my $virtiodesc = {
     optional => 1,
@@ -399,6 +409,7 @@ my $alldrive_fmt = {
     %iothread_fmt,
     %model_fmt,
     %queues_fmt,
+    %readonly_fmt,
     %scsiblock_fmt,
     %ssd_fmt,
     %wwn_fmt,
-- 
2.39.5