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

[Igor <imammedo@redhat.com>]

On Tue, 19 Sep 2017 10:59:51 -0000
"Laszlo Ersek \(Red Hat\)" <lersek@redhat.com> wrote:

> Thanks, Gerd, for the CC -- I agree, this commit (208fa0e43645) almost
> certainly breaks the VBE Shim. Displaying the patch with a bit larger
> context,
> 
> > diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> > index 22e16031b03b..59435390ba62 100644
> > --- a/hw/i386/pc.c
> > +++ b/hw/i386/pc.c
> > @@ -1442,8 +1442,11 @@ void pc_memory_init(PCMachineState *pcms,
> >  
> >      option_rom_mr = g_malloc(sizeof(*option_rom_mr));
> >      memory_region_init_ram(option_rom_mr, NULL, "pc.rom", PC_ROM_SIZE,
> >                             &error_fatal);
> > +    if (pcmc->pci_enabled) {
> > +        memory_region_set_readonly(option_rom_mr, true);
> > +    }
> >      memory_region_add_subregion_overlap(rom_memory,
> >                                          PC_ROM_MIN_VGA,
> >                                          option_rom_mr,
> >                                          1);
looking at it more, question is why do we have a separate
piece of ram mapped here that overlays system ram.
Can we remove this memory region and let guest use
underling initial memory?


> 
> and PC_ROM_MIN_VGA is #defined as 0xc0000 in "include/hw/loader.h".
> 
> OVMF places the VBE Shim into the C segment, and points the 0x10
> interrupt vector at it. See "OvmfPkg/QemuVideoDxe/VbeShim.c", function
> InstallVbeShim():
> 
> >   SegmentC = 0xC0000;
> > 
> >   [...]
> > 
> >   //
> >   // 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));
> > 
> >   //
> >   // We never added memory space during PEI or DXE for the C segment, so we
> >   // don't need to (and can't) allocate from there. Also, guest operating
> >   // systems will see a hole in the UEFI memory map there.
> >   //
> >   SegmentCPages = 4;
> > 
> >   ASSERT (sizeof mVbeShim <= EFI_PAGES_TO_SIZE (SegmentCPages));
> >   CopyMem ((VOID *)(UINTN)SegmentC, mVbeShim, sizeof mVbeShim);
> > 
> >   [...]
> > 
> >   //
> >   // Clear Write Enable (bit1), keep Read Enable (bit0) set
> >   //
> >   PciWrite8 (Pam1Address, (Pam1 & ~BIT1) | BIT0);
> > 
> >   //
> >   // Second, point the Int10h vector at the shim.
> >   //
> >   Int0x10->Segment = (UINT16) ((UINT32)SegmentC >> 4);
> >   Int0x10->Offset  = (UINT16) ((UINTN) (VbeModeInfo + 1) - SegmentC);  
>

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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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