pcie: check that slt ctrl changed before deleting

During boot, linux would sometimes overwrites control of a powered off
slot before powering it on. Unfortunately QEMU interprets that as a
power off request and ejects the device.

For example:

/x86_64-softmmu/qemu-system-x86_64 -enable-kvm -S -machine q35  \
    -device pcie-root-port,id=pcie_root_port_0,slot=2,chassis=2,addr=0x2,bus=pcie.0 \
    -monitor stdio disk.qcow2
(qemu)device_add virtio-balloon-pci,id=balloon,bus=pcie_root_port_0
(qemu)cont

Balloon is deleted during guest boot.

To fix, save control beforehand and check that power
or led state actually change before ejecting.

Note: this is more a hack than a solution, ideally we'd
find a better way to detect ejects, or move away
from ejects completely and instead monitor whether
it's safe to delete device due to e.g. its power state.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Tested-by: Igor Mammedov <imammedo@redhat.com>

1 files changed, 12 insertions, 2 deletions

diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
index b225270..f8490a0 100644
--- a/hw/pci/pcie.c
+++ b/hw/pci/pcie.c
@@ -594,7 +594,15 @@ void pcie_cap_slot_reset(PCIDevice *dev)
     hotplug_event_update_event_status(dev);
 }
 
-void pcie_cap_slot_write_config(PCIDevice *dev,
+void pcie_cap_slot_get(PCIDevice *dev, uint16_t *slt_ctl, uint16_t *slt_sta)
+{
+    uint32_t pos = dev->exp.exp_cap;
+    uint8_t *exp_cap = dev->config + pos;
+    *slt_ctl = pci_get_word(exp_cap + PCI_EXP_SLTCTL);
+    *slt_sta = pci_get_word(exp_cap + PCI_EXP_SLTSTA);
+}
+
+void pcie_cap_slot_write_config(PCIDevice *dev, uint16_t slt_ctl, uint16_t slt_sta,
                                 uint32_t addr, uint32_t val, int len)
 {
     uint32_t pos = dev->exp.exp_cap;
@@ -623,7 +631,9 @@ void pcie_cap_slot_write_config(PCIDevice *dev,
      * controller is off, it is safe to detach the devices.
      */
     if ((sltsta & PCI_EXP_SLTSTA_PDS) && (val & PCI_EXP_SLTCTL_PCC) &&
-        ((val & PCI_EXP_SLTCTL_PIC_OFF) == PCI_EXP_SLTCTL_PIC_OFF)) {
+        (val & PCI_EXP_SLTCTL_PIC_OFF) == PCI_EXP_SLTCTL_PIC_OFF &&
+        (!(slt_ctl & PCI_EXP_SLTCTL_PCC) ||
+        (slt_ctl & PCI_EXP_SLTCTL_PIC_OFF) != PCI_EXP_SLTCTL_PIC_OFF)) {
         PCIBus *sec_bus = pci_bridge_get_sec_bus(PCI_BRIDGE(dev));
         pci_for_each_device(sec_bus, pci_bus_num(sec_bus),
                             pcie_unplug_device, NULL);