[PATCH 4/9] Revert "x86: Switch QEMU over to use the bochs driver"

[Simon Glass]

Hi Bin,

On Mon, 31 Jul 2023 at 08:46, Bin Meng <bmeng.cn at gmail.com> wrote:
>
> Hi Simon,
>
> On Mon, Jul 31, 2023 at 10:37 PM Simon Glass <sjg at chromium.org> wrote:
> >
> > Hi Bin,
> >
> > On Mon, 31 Jul 2023 at 08:32, Bin Meng <bmeng.cn at gmail.com> wrote:
> > >
> > > Hi Simon,
> > >
> > > On Sat, Jul 29, 2023 at 1:32 AM Simon Glass <sjg at chromium.org> wrote:
> > > >
> > > > Hi Bin,
> > > >
> > > > On Fri, 28 Jul 2023 at 09:46, Bin Meng <bmeng.cn at gmail.com> wrote:
> > > > >
> > > > > Hi Simon,
> > > > >
> > > > > On Mon, Jul 24, 2023 at 10:52 PM Simon Glass <sjg at chromium.org> wrote:
> > > > > >
> > > > > > Unfortunately the bochs driver does not currently work with distros. It
> > > > > > causes a hang sometime between grub menu selection and the OS displaying
> > > > > > something.
> > > > >
> > > > > Does this reproduce reliably?
> > > >
> > > > Yes, it does.
> > > >
> > > > BTW I've also hit another problem with '-M accel-kvm' which hangs on
> > > > the move to 64-bit mode. Oddly if I boot U-Boot from coreboot, the
> > > > problem goes away. So perhaps coreboot is doing some x86 init which
> > > > U-Boot is missing.
> > >
> > > This indicates a kvm-x86 bug. I think you can simplify a test case and
> > > report it to the KVM mailing list.
> >
> > Firstly it doesn't really matter, since it doesn't work, so we do need
> > to revert.
>
> Agreed, but before we revert this, I would like to see we investigate
> this issue a little bit further.
>
> I enabled the grub debug output today and not sure if grub jumps to
> the kernel entry yet:
>
> kern/verifiers.c:214: string: boot, type: 2
> loader/efi/linux_sb.c:55: kernel_addr: 0x1000000 handover_offset: 0x190 params:
> 0x7ce63000
>
> >
> > Secondly I am not sure it kvm's fault, since the problem does not
> > happen with coreboot. I will see if I can isolate what coreboot is
> > doing differently, but not sure that that fix will make the release.
>
> Does the 64-bit mode switch ever work on a real x86 board? If yes,
> then it's very likely a KVM bug.

Yes it works fine on chromebook_link64, for example.

>
> If not, then we can check the coreboot to find out the difference.

Yes...do you have any ideas?

If it helps, I am using something like this:

 qemu-system-x86_64 -m 8G -smp 4  -bios /tmp/b/qemu-x86_64/u-boot.rom
-drive id=fdisk,file=root.img,if=virtio,driver=raw  -drive \
    file=/vid/software/linux/ubuntu/ubuntu-23.04-desktop-amd64.iso,if=virtio,driver=raw
 \
    -serial mon:stdio

For coreboot my script is:

UBTEST=/vid/software/devel/ubtest/
BUILD_DIR=/tmp/b/coreboot64
DISK=/vid/software/linux/ubuntu/ubuntu-23.04-desktop-amd64.iso

cp $UBTEST/coreboot.rom.in $BUILD_DIR/coreboot.rom
cbfstool $BUILD_DIR/coreboot.rom add-flat-binary \
        -f $BUILD_DIR/u-boot-x86-with-spl.bin \
        -n fallback/payload -c LZMA -l 0x1110000 -e 0x1110000

Add this in below:
#-M accel=kvm

qemu-system-x86_64 -m 2G -smp 4 -bios $BUILD_DIR/coreboot.rom -serial
mon:stdio \
        -drive id=disk,file=$DISK,if=none \
        -device ahci,id=ahci \
        -device ide-hd,drive=disk,bus=ahci.0

Regards,
Simon