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[Qemu-devel] [Bug 1685242] Re: ovmf hangs at efi with virtio-net memory

From: Laszlo Ersek \(Red Hat\)
Subject: [Qemu-devel] [Bug 1685242] Re: ovmf hangs at efi with virtio-net memory hotplug
Date: Wed, 20 Feb 2019 13:13:48 -0000

* From "debug-nonworking.log":

> GetFirstNonAddress: Pci64Base=0x8800000000 Pci64Size=0x800000000
> [...]
> PublishPeiMemory: mPhysMemAddressWidth=40 PeiMemoryCap=69644 KB
> [...]
> Type =  Mem64; Base = 0x8800000000;   Length = 0x100000;      Alignment = 
>  Base = 0x8800000000; Length = 0x4000;        Alignment = 0x3FFF;     Owner = 
> PCI [00|12|00:20]; Type = PMem64

- The 64-bit MMIO aperture starts at (512+32)GB (see "Pci64Base").
- 40 physical address bits are required (see "mPhysMemAddressWidth").
  Your PCPU has 39 (thanks for confirming that).
- The 64-bit MMIO BAR of the virtio-net-pci device is allocated at
  (512+32)GB. Will not be accessible.

* From "debug-working-222G.log":

> GetFirstNonAddress: Pci64Base=0x7800000000 Pci64Size=0x800000000
> [...]
> PublishPeiMemory: mPhysMemAddressWidth=39 PeiMemoryCap=67592 KB
> [...]
> Type =  Mem64; Base = 0x7800000000;   Length = 0x100000;      Alignment = 
>  Base = 0x7800000000; Length = 0x4000;        Alignment = 0x3FFF;     Owner = 
> PCI [00|12|00:20]; Type = PMem64

- Aperture at 480GB.
- 39 phys bits suffice.
- BAR allocated at 480GB. Will be accessible.

* From "debug-working-novirtio-net.log":

- Identical to "debug-nonworking.log", except there is no PCI device
  with a 64-bit BAR, hence no attempt is made to access the inaccessible

* Regarding why 222GB seems to be the cutoff. The base of the 64-bit
  aperture must be suitably aligned. I explained this in the
  <https://bugzilla.redhat.com/show_bug.cgi?id=1353591#c8>, in
  particular, bullet (6). If you decrease the aperture size, the
  required alignment will shrink as well, and the DIMM hotplug cutoff
  might increase. Please refer to

    -fw_cfg name=opt/ovmf/X-PciMmio64Mb,string=4096

  in <https://bugzilla.redhat.com/show_bug.cgi?id=1353591#c10>.

Right now everything appears to work by design. Closing this ticket.

** Changed in: qemu
       Status: New => Invalid

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  ovmf hangs at efi with virtio-net memory hotplug

Status in QEMU:

Bug description:
  with qemu 2.9 it hangs at the efi stage when memory-hotplug is enabled
  and it has a virtio-net devices

  the ovmf images where compiled from https://github.com/tianocore/edk2
  (current master)


  qemu-system-x86_64 -drive
  'if=pflash,unit=0,format=raw,readonly,file=./OVMF_CODE.fd' -drive
  'if=pflash,unit=1,format=raw,file=./my_OVMF_VARS.fd' -smp 1 -vga std
  -netdev 'type=tap,id=mynet' -device 'virtio-net-pci,netdev=mynet'
  -display sdl -nodefaults -m 'size=1G,slots=256,maxmem=1024G'

  interestingly, it works when you do the following:

  - omit the virtio-net-pci device
  - use seabios
  - use less maxmem, e.g. 512G

  qemu was compiled from source (v2.9.0) with following options:

  ./configure --target-list=x86_64-softmmu --disable-xen --enable-gnutls 
--enable-sdl --enable-linux-aio --enable-rbd --enable-libiscsi 
--disable-smartcard --audio-drv-list="alsa" --enable
  -spice --enable-usb-redir --enable-glusterfs --enable-libusb --disable-gtk 
--enable-xfsctl --enable-numa --disable-strip --enable-jemalloc --enable-virtfs 
--disable-libnfs --disable-fdt --disable-guest-agent --disable-guest-agent-msi

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