[PATCH qemu-server v3 5/8] hotplug: don't try to hotplug bridges

[Dominik Csapak <d.csapak@proxmox.com>]

While bridges can be hotplugged (on PCI on i440fx), no device can be
hotplugged in that afterwards. For that to work the SHPC option would
have to be enabled and the guest must support that. Since this is not
guaranteed to work and bridges don't show up in our config, this could
lead to bridges added that are not represented in the config.

To be on the safe side, simply don't allow hotplugging bridges at all.
Luckily, the only bridge we ever tried hotplugging (since machine
version 2.3) was pci.4 which only houses scsihw2/3/4 at the moment.

These are only used for scsiX where X > 13 and only if the scsihw is an
LSI controller, so not very likely to occur.

This fixes an issue where trying to hotplug a scsi disk with index >=14
on a i440fx machine with an LSI scsi controller would leave the bridge
around after failing to add the scsi controller, and the machine would
subsequently crash on live migration.

Fixes: 2513b862 (fix #2566: increase scsi limit to 31)
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 src/PVE/QemuServer.pm | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
index ce3eea4d..fbb0a23e 100644
--- a/src/PVE/QemuServer.pm
+++ b/src/PVE/QemuServer.pm
@@ -3899,13 +3899,11 @@ sub vm_devices_list {
 sub vm_deviceplug {
     my ($storecfg, $conf, $vmid, $deviceid, $device, $arch, $machine_type) = @_;
 
-    my $q35 = PVE::QemuServer::Machine::machine_type_is_q35($conf);
-
     my $devices_list = vm_devices_list($vmid);
     return 1 if defined($devices_list->{$deviceid});
 
-    # add PCI bridge if we need it for the device
-    qemu_add_pci_bridge($storecfg, $conf, $vmid, $deviceid, $arch, $machine_type);
+    # we can't hotplug bridges, so check if the necessary one exists
+    assert_pci_bridge_present($vmid, $deviceid);
 
     if ($deviceid eq 'tablet') {
         qemu_deviceadd($vmid, print_tabletdevice_full($conf, $arch));
@@ -3992,13 +3990,6 @@ sub vm_deviceplug {
             warn $@ if $@;
             die $err;
         }
-    } elsif (!$q35 && $deviceid =~ m/^(pci\.)(\d+)$/) {
-        my $bridgeid = $2;
-        my $pciaddr = print_pci_addr($deviceid, undef, $arch);
-        my $devicefull = "pci-bridge,id=pci.$bridgeid,chassis_nr=$bridgeid$pciaddr";
-
-        qemu_deviceadd($vmid, $devicefull);
-        qemu_deviceaddverify($vmid, $deviceid);
     } else {
         die "can't hotplug device '$deviceid'\n";
     }
@@ -4215,8 +4206,8 @@ sub qemu_deletescsihw {
     return 1;
 }
 
-sub qemu_add_pci_bridge {
-    my ($storecfg, $conf, $vmid, $device, $arch, $machine_type) = @_;
+sub assert_pci_bridge_present {
+    my ($vmid, $device) = @_;
 
     my $bridgeid = PVE::QemuServer::PCI::get_pci_bridge_for_device($device);
     return 1 if !defined($bridgeid) || $bridgeid < 1;
@@ -4225,7 +4216,7 @@ sub qemu_add_pci_bridge {
     my $devices_list = vm_devices_list($vmid);
 
     if (!defined($devices_list->{$bridge})) {
-        vm_deviceplug($storecfg, $conf, $vmid, $bridge, $arch, $machine_type);
+        die "can't hotplug bridge necessary for '$device'\n";
     }
 
     return 1;
-- 
2.47.3