qemu-ga: make get-fsinfo work over pci bridges

Iterate over the PCI bridges to lookup the PCI device associated with
the block device.

This allows to lookup the driver under the following syspath:
/sys/devices/pci0000:00/0000:00:02.2/0000:03:00.0/virtio2/block/vda/vda3

It also works with an "old-style" Q35 libvirt hierarchy: root complex
-> DMI-PCI bridge -> PCI-PCI bridge -> virtio controller, ex:
/sys/devices/pci0000:00/0000:00:03.0/0000:01:01.0/0000:02:01.0/virtio1/block/vda/vda3

The setup can be reproduced with the following qemu command line
(Thanks Marcel for help):

qemu-system-x86_64 -M q35 \
  -device i82801b11-bridge,id=dmi2pci_bridge,bus=pcie.0
  -device pci-bridge,id=pci_bridge,bus=dmi2pci_bridge,addr=0x1,chassis_nr=1
  -device virtio-blk-pci,scsi=off,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,bus=pci_bridge,addr=0x1

For consistency with other syspath-related debug messages, replace a
\"%s\" in the message with '%s'.

Fixes:
https://bugzilla.redhat.com/show_bug.cgi?id=1567041

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

1 files changed, 19 insertions, 4 deletions

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index ae8535e497..7b7c78d85a 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -876,13 +876,28 @@ static void build_guest_fsinfo_for_real_device(char const *syspath,
     p = strstr(syspath, "/devices/pci");
     if (!p || sscanf(p + 12, "%*x:%*x/%x:%x:%x.%x%n",
                      pci, pci + 1, pci + 2, pci + 3, &pcilen) < 4) {
-        g_debug("only pci device is supported: sysfs path \"%s\"", syspath);
+        g_debug("only pci device is supported: sysfs path '%s'", syspath);
         return;
     }
 
-    driver = get_pci_driver(syspath, (p + 12 + pcilen) - syspath, errp);
-    if (!driver) {
-        goto cleanup;
+    p += 12 + pcilen;
+    while (true) {
+        driver = get_pci_driver(syspath, p - syspath, errp);
+        if (driver && (g_str_equal(driver, "ata_piix") ||
+                       g_str_equal(driver, "sym53c8xx") ||
+                       g_str_equal(driver, "virtio-pci") ||
+                       g_str_equal(driver, "ahci"))) {
+            break;
+        }
+
+        if (sscanf(p, "/%x:%x:%x.%x%n",
+                          pci, pci + 1, pci + 2, pci + 3, &pcilen) == 4) {
+            p += pcilen;
+            continue;
+        }
+
+        g_debug("unsupported driver or sysfs path '%s'", syspath);
+        return;
     }
 
     p = strstr(syspath, "/target");