Re: KVM call minutes for Feb 1

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On 02/01/2011 11:03 AM, Jan Kiszka wrote:
On 2011-02-01 17:53, Anthony Liguori wrote:
On 02/01/2011 10:36 AM, Jan Kiszka wrote:
On 2011-02-01 16:54, Chris Wright wrote:

KVM upstream merge: status, plans, coordination
- Jan has a git tree, consolidating
- qemu-kvm io threading is still an issue
- Anthony wants to just merge
    - concerns with non-x86 arch and merge
    - concerns with big-bang patch merge and following stability
- post 0.14 conversion to glib mainloop, non-upstreamed qemu-kvm will be
    a problem if it's not there by then
- testing and nuances are still an issue (e.g. stefan berger's mmio read issue)
- qemu-kvm still evolving, needs to get sync'd or it will keep diverging
- 2 implementations of main init, cpu init, Jan has merged them into one
    - qemu-kvm-x86.c file that's only a few hundred lines
- review as one patch to see the fundamental difference

More precisely, my current work flow is to pick some function(s), e.g.
kvm_cpu_exec/kvm_run, and start wondering "What needs to be done to
upstream so that qemu-kvm could use that implementation?". If they
differ, the reasons need to be understood and patched away, either by
fixing/enhancing upstream or simplifying qemu-kvm. Once the upstream
changes are merged back, a qemu-kvm patch is posted to switch to that
version.

Any help will be welcome, either via review of my subtle regressions or
on resolving concrete differences.

E.g. posix-aio-compat.c: Why does qemu-kvm differ here? If it's because
of its own iothread code, can we wrap that away or do we need to
consolidate the threading code first? Or do we need to fix something in
upstream?

I bet it's the eventfd thing.  It's arbitrary.  If you've got a small
diff post your series, I'd be happy to take a look at it and see what I
can explain.

Looks like it's around signalfd and its emulation:

I really meant the compatfd thing.

signalfd can't really be emulated properly so in upstream we switched to a pipe() which Avi didn't like.

But with glib, this all goes away anyway so we should just drop the qemu-kvm changes and use the upstream version. Once we enable I/O thread in qemu.git, we no longer need to use signals for I/O completion which I think everyone would agree is a better solution.

Regards,

Anthony Liguori
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