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[Bug 1879175] Re: GVTd not working (black screen) after upgrade to qemu-


From: TheCatFelix
Subject: [Bug 1879175] Re: GVTd not working (black screen) after upgrade to qemu-5.0.0
Date: Sun, 17 May 2020 17:05:51 -0000

** Summary changed:

- GVTd not working after upgrade to qemu-5.0.0
+ GVTd not working (black screen) after upgrade to qemu-5.0.0

-- 
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https://bugs.launchpad.net/bugs/1879175

Title:
  GVTd not working (black screen) after upgrade to qemu-5.0.0

Status in QEMU:
  New

Bug description:
  Hi QEMU team,

  
  === Problem Summary ===

  I have recently upgraded from QEMU-3.1.0 to to QEMU-5.0.0 on Debian
  Unstable. Unfortunately GVTd (legacy passthrough of the integrated
  intel gpu) stopped working correctly. The guest can still see and
  loads the driver for the GPU, but the screen stays black.

  The following is the version used:

  $ /usr/bin/qemu-system-x86_64 --version
  QEMU emulator version 5.0.0 (Debian 1:5.0-5)
  Copyright (c) 2003-2020 Fabrice Bellard and the QEMU Project developers


  === Investigation/Triage done so far ===

  Running QEMU with trace flags enabled shows the following behavior
  change for the same VM (left: 3.1.0, right: 5.0.0):

  vfio_realize  (0000:00:02.0) group 1                                          
                          vfio_realize  (0000:00:02.0) group 1
  vfio_listener_region_add_ram region_add [ram] 0x0 - 0xbffff [0x7f5b41e00000]  
                     |    vfio_listener_region_add_ram region_add [ram] 0x0 - 
0xbffff [0x7f2bb1e00000]
  vfio_listener_region_add_ram region_add [ram] 0xc0000 - 0xdffff 
[0x7f5d1d400000]                   |    vfio_listener_region_add_ram region_add 
[ram] 0xc0000 - 0xdffff [0x7f2d7c800000]
  vfio_listener_region_add_ram region_add [ram] 0xe0000 - 0xfffff 
[0x7f5d1d620000]                   |    vfio_listener_region_add_ram region_add 
[ram] 0xe0000 - 0xfffff [0x7f2d84220000]
  vfio_listener_region_add_ram region_add [ram] 0x100000 - 0xbfffffff 
[0x7f5b41f00000]               |    vfio_listener_region_add_ram region_add 
[ram] 0x100000 - 0xbfffffff [0x7f2bb1f00000]
  vfio_listener_region_add_skip SKIPPING region_add 0xfec00000 - 0xfec00fff     
                          vfio_listener_region_add_skip SKIPPING region_add 
0xfec00000 - 0xfec00fff
  vfio_listener_region_add_skip SKIPPING region_add 0xfee00000 - 0xfeefffff     
                          vfio_listener_region_add_skip SKIPPING region_add 
0xfee00000 - 0xfeefffff
  vfio_listener_region_add_ram region_add [ram] 0xfffc0000 - 0xffffffff 
[0x7f5d1d600000]             |    vfio_listener_region_add_ram region_add [ram] 
0xfffc0000 - 0xffffffff [0x7f2d84200000]
  vfio_listener_region_add_ram region_add [ram] 0x100000000 - 0x201ffffff 
[0x7f5c01e00000]           |    vfio_listener_region_add_ram region_add [ram] 
0x100000000 - 0x201ffffff [0x7f2c71e00000]
  vfio_mdev  (0000:00:02.0) is_mdev 0                                           
                          vfio_mdev  (0000:00:02.0) is_mdev 0
  vfio_get_device Device 0000:00:02.0 flags: 3, regions: 12, irqs: 5            
                          vfio_get_device Device 0000:00:02.0 flags: 3, 
regions: 12, irqs: 5
  vfio_region_setup Device 0000:00:02.0, region 0 "0000:00:02.0 BAR 0", flags: 
0x7, offset: 0x0, s        vfio_region_setup Device 0000:00:02.0, region 0 
"0000:00:02.0 BAR 0", flags: 0x7, offset: 0x0, s
  vfio_region_setup Device 0000:00:02.0, region 1 "0000:00:02.0 BAR 1", flags: 
0x0, offset: 0x1000        vfio_region_setup Device 0000:00:02.0, region 1 
"0000:00:02.0 BAR 1", flags: 0x0, offset: 0x1000
  vfio_region_setup Device 0000:00:02.0, region 2 "0000:00:02.0 BAR 2", flags: 
0x7, offset: 0x2000        vfio_region_setup Device 0000:00:02.0, region 2 
"0000:00:02.0 BAR 2", flags: 0x7, offset: 0x2000
  vfio_region_setup Device 0000:00:02.0, region 3 "0000:00:02.0 BAR 3", flags: 
0x0, offset: 0x3000        vfio_region_setup Device 0000:00:02.0, region 3 
"0000:00:02.0 BAR 3", flags: 0x0, offset: 0x3000
  vfio_region_setup Device 0000:00:02.0, region 4 "0000:00:02.0 BAR 4", flags: 
0x3, offset: 0x4000        vfio_region_setup Device 0000:00:02.0, region 4 
"0000:00:02.0 BAR 4", flags: 0x3, offset: 0x4000
  vfio_region_setup Device 0000:00:02.0, region 5 "0000:00:02.0 BAR 5", flags: 
0x0, offset: 0x5000        vfio_region_setup Device 0000:00:02.0, region 5 
"0000:00:02.0 BAR 5", flags: 0x0, offset: 0x5000
  vfio_populate_device_config Device 0000:00:02.0 config:                       
                          vfio_populate_device_config Device 0000:00:02.0 
config:
   0x1000, offset: 0x70000000000, flags: 0x3                                    
                           0x1000, offset: 0x70000000000, flags: 0x3
  vfio_region_mmap Region 0000:00:02.0 BAR 0 mmaps[0] [0x0 - 0xffffff]          
                          vfio_region_mmap Region 0000:00:02.0 BAR 0 mmaps[0] 
[0x0 - 0xffffff]
  vfio_region_mmap Region 0000:00:02.0 BAR 2 mmaps[0] [0x0 - 0xfffffff]         
                          vfio_region_mmap Region 0000:00:02.0 BAR 2 mmaps[0] 
[0x0 - 0xfffffff]
  vfio_check_pm_reset 0000:00:02.0 Supports PM reset                            
                          vfio_check_pm_reset 0000:00:02.0 Supports PM reset
  vfio_msi_setup 0000:00:02.0 PCI MSI CAP @0xac                                 
                          vfio_msi_setup 0000:00:02.0 PCI MSI CAP @0xac
  vfio_check_pcie_flr 0000:00:02.0 Supports FLR via PCIe cap                    
                          vfio_check_pcie_flr 0000:00:02.0 Supports FLR via 
PCIe cap
  vfio_get_dev_region 0000:00:02.0 index 9, 80008086/18                         
                     <
  vfio_get_dev_region 0000:00:02.0 index 9, 80008086/18                         
                     <
  vfio_get_dev_region 0000:00:02.0 index 10, 80008086/28                        
                     <
  vfio_get_dev_region 0000:00:02.0 index 9, 80008086/18                         
                     <
  vfio_get_dev_region 0000:00:02.0 index 10, 80008086/28                        
                     <
  vfio_get_dev_region 0000:00:02.0 index 11, 80008086/38                        
                     <
  vfio_listener_region_del region_del 0x0 - 0xbffff                             
                     <
  vfio_listener_region_add_ram region_add [ram] 0x0 - 0x9ffff [0x7f5b41e00000]  
                     <
  vfio_listener_region_add_skip SKIPPING region_add 0xa0000 - 0xbffff           
                     <
  vfio_pci_igd_lpc_bridge_enabled 0000:00:02.0                                  
                     <
  vfio_pci_igd_host_bridge_enabled 0000:00:02.0                                 
                     <
  vfio_pci_igd_opregion_enabled 0000:00:02.0                                    
                     <
  vfio_pci_igd_bdsm_enabled 0000:00:02.0 40MB                                   
                     <
  vfio_intx_enable_kvm  (0000:00:02.0) KVM INTx accel enabled                   
                          vfio_intx_enable_kvm  (0000:00:02.0) KVM INTx accel 
enabled
  vfio_intx_enable  (0000:00:02.0)                                              
                          vfio_intx_enable  (0000:00:02.0)
   0x100, offset: 0x70000000000, flags: 0x3                                     
                           0x100, offset: 0x70000000000, flags: 0x3
  vfio_populate_device_get_irq_info_failure VFIO_DEVICE_GET_IRQ_INFO failure: 
Invalid argument            vfio_populate_device_get_irq_info_failure 
VFIO_DEVICE_GET_IRQ_INFO failure: Invalid argument
  vfio_pci_reset  (0000:00:02.0)                                                
                          vfio_pci_reset  (0000:00:02.0)
  vfio_intx_disable_kvm  (0000:00:02.0) KVM INTx accel disabled                 
                          vfio_intx_disable_kvm  (0000:00:02.0) KVM INTx accel 
disabled
  vfio_region_mmaps_set_enabled Region 0000:00:02.0 BAR 0 mmaps enabled: 1      
                          vfio_region_mmaps_set_enabled Region 0000:00:02.0 BAR 
0 mmaps enabled: 1
  vfio_region_mmaps_set_enabled Region 0000:00:02.0 BAR 2 mmaps enabled: 1      
                          vfio_region_mmaps_set_enabled Region 0000:00:02.0 BAR 
2 mmaps enabled: 1
  vfio_region_mmaps_set_enabled Region 0000:00:02.0 BAR 4 mmaps enabled: 1      
                          vfio_region_mmaps_set_enabled Region 0000:00:02.0 BAR 
4 mmaps enabled: 1
  vfio_intx_disable  (0000:00:02.0)                                             
                          vfio_intx_disable  (0000:00:02.0)
  vfio_pci_write_config  (0000:00:02.0, @0x4, 0x0, len=0x2)                     
                          vfio_pci_write_config  (0000:00:02.0, @0x4, 0x0, 
len=0x2)
  vfio_listener_region_del region_del 0x0 - 0x9ffff                             
                     <
  vfio_listener_region_del_skip SKIPPING region_del 0xa0000 - 0xbffff           
                     <
  vfio_listener_region_add_ram region_add [ram] 0x0 - 0xbffff [0x7f5b41e00000]  
                     <
  vfio_pci_reset_flr 0000:00:02.0 FLR/VFIO_DEVICE_RESET                         
                          vfio_pci_reset_flr 0000:00:02.0 FLR/VFIO_DEVICE_RESET
  vfio_intx_enable  (0000:00:02.0)                                              
                          vfio_intx_enable  (0000:00:02.0)
  vfio_listener_region_del region_del 0x0 - 0xbffff                             
                          vfio_listener_region_del region_del 0x0 - 0xbffff
  vfio_listener_region_del region_del 0xc0000 - 0xdffff                         
                          vfio_listener_region_del region_del 0xc0000 - 0xdffff
  vfio_listener_region_del region_del 0xe0000 - 0xfffff                         
                          vfio_listener_region_del region_del 0xe0000 - 0xfffff
  vfio_listener_region_del region_del 0x100000 - 0xbfffffff                     
                          vfio_listener_region_del region_del 0x100000 - 
0xbfffffff
  vfio_listener_region_add_ram region_add [ram] 0x0 - 0xcffff [0x7f5b41e00000]  
                     |    vfio_listener_region_add_ram region_add [ram] 0x0 - 
0xcffff [0x7f2bb1e00000]

  We can see here, the following key lines are not printed in 5.0.0:

  vfio_pci_igd_lpc_bridge_enabled 0000:00:02.0                                  
                     <
  vfio_pci_igd_host_bridge_enabled 0000:00:02.0                                 
                     <
  vfio_pci_igd_opregion_enabled 0000:00:02.0                                    
                     <
  vfio_pci_igd_bdsm_enabled 0000:00:02.0 40MB                                   
                     <

  Looking through the code and bisecting the problem (I can provide more
  detail if helpful), shows the following ifdef statement lines
  introduce the problem:

  https://github.com/qemu/qemu/blob/master/hw/vfio/pci-quirks.c#L1253

    1246  void vfio_bar_quirk_setup(VFIOPCIDevice *vdev, int nr)
    1247  {
    1248      vfio_probe_ati_bar4_quirk(vdev, nr);
    1249      vfio_probe_ati_bar2_quirk(vdev, nr);
    1250      vfio_probe_nvidia_bar5_quirk(vdev, nr);
    1251      vfio_probe_nvidia_bar0_quirk(vdev, nr);
    1252      vfio_probe_rtl8168_bar2_quirk(vdev, nr);
    1253  #ifdef CONFIG_VFIO_IGD
    1254      vfio_probe_igd_bar4_quirk(vdev, nr);
    1255  #endif
    1256  }

  This was added by the following commits:

  https://github.com/qemu/qemu/commit/29d62771c81d8fd244a67c14a1d968c268d3fb19
  #diff-38093e21794c7a4987feb71e498dbdc6

  Reading through the commit message, I suspect the something may be
  happening with the Kconfig switches mentioned there.


  === Validation/Workaround ===

  I have rebuilt the package with the following two changes:

  root@debian:/home/test/src# diff debian_*/qemu-5.0/hw/vfio/pci-quirks.c
  0a1
  > #define CONFIG_VFIO_IGD y
  root@debian:/home/test/src# diff debian_*/qemu-5.0/hw/vfio/Kconfig
  42c42
  <     default y if PC_PCI
  ---
  >     default y
  root@debian:/home/test/src#

  GVTd started working fine again (Screen shows output again).

  I have tried with either change alone:

  - with only the ifdef in pci-quirks.c compilation fails with linker errors
  - with only the Kconfig it compiles, but GVTd still does not work (black 
screen)


  Please take a look and thank you very much for a fantastic product!

  TheCatFelix

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