Re: [Qemu-devel] [Bug 1715700] Re: Windows 7 guest won't boot on qemu 2.10 (works on 2.9)

["Laszlo Ersek \(Red Hat\)" <lersek@redhat.com>]

On 09/19/17 13:49, Gerd Hoffmann wrote:
> ovmf seems to not touch pam configuration, so rom remains mapped.

I don't understand; the code that I quoted above -- and that LaunchPad
messed up -- explicitly changes the PAM registers:

  //
  // Put the shim in place first.
  //
  Pam1Address = PCI_LIB_ADDRESS (0, 0, 0, 0x5A);
  //
  // low nibble covers 0xC0000 to 0xC3FFF
  // high nibble covers 0xC4000 to 0xC7FFF
  // bit1 in each nibble is Write Enable
  // bit0 in each nibble is Read Enable
  //
  Pam1 = PciRead8 (Pam1Address);
  PciWrite8 (Pam1Address, Pam1 | (BIT1 | BIT0));

...

  //
  // Clear Write Enable (bit1), keep Read Enable (bit0) set
  //
  PciWrite8 (Pam1Address, (Pam1 & ~BIT1) | BIT0);

> seabios in contrast maps the address range to ram instead.
> IIRC ovmf does that too in CSM mode.
> So, yes, probably this is fixable in ovmf.

I don't see how.

Thanks
Laszlo

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https://bugs.launchpad.net/bugs/1715700

Title:
  Windows 7 guest won't boot on qemu 2.10 (works on 2.9)

Status in QEMU:
  New

Bug description:
  Qemu version: 2.10 stable.
  Guest: Windows 7 SP1 x64, virtio drivers are already installed in the guest.
  Command line:
  qemu-system-x86_64 \
      -nodefaults \
      -nodefconfig \
      -machine type=q35,accel=kvm \
      -enable-kvm \
      -cpu host \
      -m 2048 \
      -vga virtio \
      -boot menu=on \
      -smbios file=/path/dmidecode_BIOS.bin \
      -acpitable file=/path/acpi_slic.bin \
      -bios /path/OVMF_CODE.fd \
      -net none \
      -drive if=virtio,media=disk,file=/media/win7.qcow2 \
      -device pcie-root-port \
      -device ich9-usb-ehci1 \
      -device ich9-usb-uhci1 \
      -device ich9-usb-uhci2 \
      -device ich9-usb-uhci3

  Windows hangs at boot with waving flag screen (flag doesn't freeze,
  keeps waving indefinitely). Same command line boots fine with Qemu
  2.9. I tried changing machine type to pc-q35-2.9 - same result.

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