F19: replacing chardev patches with upstream ones

[Amit Shah]

Hello,

Fedora has carried flow control patches for qemu chardevs since a very
long time now.  They weren't upstream, and they were required for
spice, usb-redir to work properly and not freeze the guest.

Upstream qemu has now merged an alternative implementation of the same
concept, and most of the bugs have been shaken out upstream (we don't
know of any known bugs now).  So I'm of the view we should replace
the older patches in F19's qemu with the backport of the newer,
upstream ones.

Is this fine?  I can work with Cole / Hans who have been keeping the
older patches uptodate on Fedora to replace the patches.

Thanks,

		Amit

[Hans de Goede]

Hi,

On 04/23/2013 07:57 AM, Amit Shah wrote:
>  Hello,
>
>  Fedora has carried flow control patches for qemu chardevs since a very
>  long time now.  They weren't upstream, and they were required for
>  spice, usb-redir to work properly and not freeze the guest.
>
>  Upstream qemu has now merged an alternative implementation of the same
>  concept, and most of the bugs have been shaken out upstream (we don't
>  know of any known bugs now).  So I'm of the view we should replace
>  the older patches in F19's qemu with the backport of the newer,
>  upstream ones.
>
>  Is this fine? 
This is fine by me.

Regards,

Hans

[Cole Robinson]

On 04/23/2013 01:57 AM, Amit Shah wrote:
>  Hello,
>  
>  Fedora has carried flow control patches for qemu chardevs since a very
>  long time now.  They weren't upstream, and they were required for
>  spice, usb-redir to work properly and not freeze the guest.
>  
>  Upstream qemu has now merged an alternative implementation of the same
>  concept, and most of the bugs have been shaken out upstream (we don't
>  know of any known bugs now).  So I'm of the view we should replace
>  the older patches in F19's qemu with the backport of the newer,
>  upstream ones.
>  
>  Is this fine?  I can work with Cole / Hans who have been keeping the
>  older patches uptodate on Fedora to replace the patches.
>   
If the backport is fairly clean and self contained it should be okay, but
can't say I'm excited about it. What's the benefit besides more testing of
the
new code? Yes we get to drop the old patches but at this point they are a long
tested known quantity. If it was a month ago I'd be less resistant but this
will be past the alpha.

I'll leave it to your discretion but if the backport is pulling in unrelated
patches so things apply cleanly, or needs non-trivial alteration to work on
1.4, we should re-evaluate.

Thanks,
Cole

[Amit Shah]

On (Tue) 23 Apr 2013 [10:32:56], Cole Robinson wrote:
>  On 04/23/2013 01:57 AM, Amit Shah wrote:
>  > Hello,
>  > 
>  > Fedora has carried flow control patches for qemu chardevs since a very
>  > long time now.  They weren't upstream, and they were required for
>  > spice, usb-redir to work properly and not freeze the guest.
>  > 
>  > Upstream qemu has now merged an alternative implementation of the same
>  > concept, and most of the bugs have been shaken out upstream (we don't
>  > know of any known bugs now).  So I'm of the view we should replace
>  > the older patches in F19's qemu with the backport of the newer,
>  > upstream ones.
>  > 
>  > Is this fine?  I can work with Cole / Hans who have been keeping the
>  > older patches uptodate on Fedora to replace the patches.
>  > 
>  
>  If the backport is fairly clean and self contained it should be okay, but
>  can't say I'm excited about it. What's the benefit besides more testing of
> the
>  new code? Yes we get to drop the old patches but at this point they are a long
>  tested known quantity. If it was a month ago I'd be less resistant but this
>  will be past the alpha. 
Yes, I was concerned about the timing too.

>  I'll leave it to your discretion but if the backport is pulling
> in unrelated
>  patches so things apply cleanly, or needs non-trivial alteration to work on
>  1.4, we should re-evaluate. 
I haven't tried the backport yet.

Since people haven't been finding bugs in the older code, it's
obviously safer to just keep it and drop all the patches in rawhide
once we rebase to qemu-1.5 (1.5 will contain all the new upstream
work).  OTOH getting testing for the new code will be a big positive.
> From all indications, we've ironed out the bugs in the most-used
areas.  There might be some lurking in corner cases, and we do have
some time till the final release.

Looking at the current state, I am inclined to push the upstream
changes since we've been rigorously testing for regressions (and
everything looks settled now).

		Amit

[Amit Shah]

On (Tue) 23 Apr 2013 [20:41:03], Amit Shah wrote:
>  On (Tue) 23 Apr 2013 [10:32:56], Cole Robinson wrote:
>  > On 04/23/2013 01:57 AM, Amit Shah wrote:
>  > > Hello,
>  > > 
>  > > Fedora has carried flow control patches for qemu chardevs since a very
>  > > long time now.  They weren't upstream, and they were required for
>  > > spice, usb-redir to work properly and not freeze the guest.
>  > > 
>  > > Upstream qemu has now merged an alternative implementation of the same
>  > > concept, and most of the bugs have been shaken out upstream (we don't
>  > > know of any known bugs now).  So I'm of the view we should replace
>  > > the older patches in F19's qemu with the backport of the newer,
>  > > upstream ones.
>  > > 
>  > > Is this fine?  I can work with Cole / Hans who have been keeping the
>  > > older patches uptodate on Fedora to replace the patches.
>  > > 
>  > 
>  > If the backport is fairly clean and self contained it should be okay, but
>  > can't say I'm excited about it. What's the benefit besides more testing
> of the
>  > new code? Yes we get to drop the old patches but at this point they are a long
>  > tested known quantity. If it was a month ago I'd be less resistant but this
>  > will be past the alpha.
>  
>  Yes, I was concerned about the timing too. 
Cole mentioned on IRC about rawhide virt-preview, which I agree will
be a good idea to get this code into users' hands.  So let's drop the
backport idea for now -- I'm quite relieved :)

		Amit

[Richard W.M. Jones]

On Tue, Apr 23, 2013 at 11:27:09AM +0530, Amit Shah wrote:
>  Hello,
>  
>  Fedora has carried flow control patches for qemu chardevs since a very
>  long time now.  They weren't upstream, and they were required for
>  spice, usb-redir to work properly and not freeze the guest.
>  
>  Upstream qemu has now merged an alternative implementation of the same
>  concept, and most of the bugs have been shaken out upstream (we don't
>  know of any known bugs now).  So I'm of the view we should replace
>  the older patches in F19's qemu with the backport of the newer,
>  upstream ones.
>  
>  Is this fine?  I can work with Cole / Hans who have been keeping the
>  older patches uptodate on Fedora to replace the patches. 
Would this affect virtio-serial (ie. libguestfs)?

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org

[Amit Shah]

On (Sat) 27 Apr 2013 [21:15:54], Richard W.M. Jones wrote:
>  On Tue, Apr 23, 2013 at 11:27:09AM +0530, Amit Shah wrote:
>  > Hello,
>  > 
>  > Fedora has carried flow control patches for qemu chardevs since a very
>  > long time now.  They weren't upstream, and they were required for
>  > spice, usb-redir to work properly and not freeze the guest.
>  > 
>  > Upstream qemu has now merged an alternative implementation of the same
>  > concept, and most of the bugs have been shaken out upstream (we don't
>  > know of any known bugs now).  So I'm of the view we should replace
>  > the older patches in F19's qemu with the backport of the newer,
>  > upstream ones.
>  > 
>  > Is this fine?  I can work with Cole / Hans who have been keeping the
>  > older patches uptodate on Fedora to replace the patches.
>  
>  Would this affect virtio-serial (ie. libguestfs)? 
Yes, it affects everything that uses chardevs, including
virtio-serial.  Without the flow control patches, guest writes to
virtio-serial ports could freeze the guest.  We've carried
non-upstream patches in Fedora for a long time now.

		Amit