Re: [Qemu-devel] [PULL 22/55] q35: ioapic: add support for emulated IOAPIC IR

[Emilio G. Cota]

On Fri, Nov 11, 2016 at 18:17:05 -0500, Peter Xu wrote:
> > This commit (which sits between 2.6 and 2.7) doesn't let me boot a
> > buildroot-generated x86_64 image when QEMU is configured with
> > --with-coroutine=gthread (it deadlocks on the BQL shortly after
> > the framebuffer comes up.)
> > 
> > Is this something we should worry about? I see in the configure
> > script that --with-coroutine=gthread "is not functional enough to run
> > QEMU proper". My goal is to use thread sanitizer (tsan) to test
> > mttcg for x86-64. Unfortunately, tsan blows with ucontext coroutines.
> 
> I tried to build QEMU using:
> 
>   ../configure --target-list=x86_64-softmmu --with-coroutine=gthread
> 
> with above commit. QEMU binary can boot well with either KVM or TCG
> (with no QEMU paramter, so only BIOS is up). However if I provide a
> image disk to the VM, KVM version worked, but TCG didn't.
> 
> Is this the same error you have encountered?

KVM works fine for me in all cases.

With TCG, QEMU freezes when booting linux, when the fb comes up (right
after the resolution changes). This is the last output I see from the kernel:
  http://imgur.com/YWHUM9x

I tried booting with -nographic but it still freezes.

I'm booting a buildroot-generated image with:

x86_64-softmmu/qemu-system-x86_64 -no-reboot -M pc \
        -kernel /path/to/buildroot/output/images/bzImage \
        -drive 
file=/path/to/buildroot/output/images/rootfs.ext2,if=virtio,format=raw \
        -append 'root=/dev/vda' -net nic,model=virtio -net 
user,hostfwd=tcp::10022-:22 \
        -smp 1 -m 4G

> I also tried to test with exactly the same build parameters with the
> previous commit of above (09cd058a2c, "intel_iommu: get rid of {0}
> initializers"), it has the same problem (TCG version cannot boot guest
> kernel if I provide a disk as parameter).

Hmm that's interesting, on my end 09cd05^ works well 100% of the time
w/ TCG.

> Do we still support gthread as coroutine backend? And to what extend
> do we support it?

I don't know :( That's why I sent the message.

I'll investigate further.

Thanks,

                Emilio