From: Jiqian Chen <Jiqian.Chen@amd.com>

Fix bug imported by 27ce0f3afc9dd ("fix Power Management Control Register for PCI Express virtio devices"
After this change, observe that QEMU may erroneously clear the power status of the device,
or may erroneously clear non writable registers, such as NO_SOFT_RESET, etc.

Only state of PM_CTRL is writable.
Only when flag VIRTIO_PCI_FLAG_INIT_PM is set, need to reset state.

Fixes: 27ce0f3afc9dd ("fix Power Management Control Register for PCI Express virtio devices"
Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
Message-Id: <20240515073526.17297-2-Jiqian.Chen@amd.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/virtio/virtio-pci.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index cffc7efcae..7d62e92365 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -2306,10 +2306,16 @@ static void virtio_pci_bus_reset_hold(Object *obj, ResetType type)
     virtio_pci_reset(qdev);
 
     if (pci_is_express(dev)) {
+        VirtIOPCIProxy *proxy = VIRTIO_PCI(dev);
+
         pcie_cap_deverr_reset(dev);
         pcie_cap_lnkctl_reset(dev);
 
-        pci_set_word(dev->config + dev->exp.pm_cap + PCI_PM_CTRL, 0);
+        if (proxy->flags & VIRTIO_PCI_FLAG_INIT_PM) {
+            pci_word_test_and_clear_mask(
+                dev->config + dev->exp.pm_cap + PCI_PM_CTRL,
+                PCI_PM_CTRL_STATE_MASK);
+        }
     }
 }
 
-- 
MST