[Qemu-devel] Re: KVM call agenda for Mar 23

[Juan Quintela]

Juan Quintela <address@hidden> wrote:
> Chris Wright <address@hidden> wrote:
>> Please send in any agenda items you are interested in covering.
>>
>> Yes, usability is a valid topic esp. if you promise to come w/ GUI patches.
>
> - migration (we didn't end last week)

I told last Tuesday that I will look at the latest vmstate changes
This is a search of VMSTATE/qemu_get() of commits of this year.

The Anthony/Avi? (I don't remember) of checking if feature was used
_before_ sending it would have fixed all of them.  Indeed the balloon
statistics one.

Problem is that if we go this route we need:
- subsections (is the easy way to go), almost there
- being able to change the version_id of the _current_ section.  That is
  _not easy_ with current design (we can't rewind the file).  That means
  that we need something like imprement vmstet_save() to a buffer, check
  the function there and push it from there.

This still don't fixes all problems, because what do we do when we have
two independent features and only one is needed?

vmstate-foo: id = 4

vmstate-foo: id = 5
  bar1 subsection (optional depending of this function)

vmstate-foo: id = 6
  bar1 subsection (optional depending of this function)
  bar2 subsection (optional depending of this other function)


what do we do if bar2 is needed but bar1 is not needed?

Other option is just sent:

vmstate-foo: id = 4
  bar1 subsection (optional depending of this function)
  bar2 subsection (optional depending of this other function)

(same version id for the general one).  As subsections would get a
 different id_section, that could even work on devices that don't know
 about this new sections, because they would find a ->section_id that
 they don't understand/don't expect there).

What do you think?

Later, Juan.


commit ed487bb1d69040b9dac64a4fc076d8dd82b131d6
Author: Marcelo Tosatti <address@hidden>
Date:   Thu Feb 11 18:19:44 2010 -0200

    ide save/restore pio/atapi cmd transfer fields and io buffer
    
    Save/restore information necessary to continue in progress PIO/ATAPI CMD
    transfers.
    
    This includes the IO buffer.

- we can test if lenght != 0 and not sent it in that case.  no infrastructure 
to do it otherwise.

commit 31827373f03b0ff1550d45ddef0ca1305a2ae70d
Author: Jan Kiszka <address@hidden>
Date:   Mon Dec 14 12:26:17 2009 +0100

    kvm: x86: Use separate exception_injected CPUState field
    
    Marcelo correctly remarked that there are usage conflicts between QEMU
    core code and KVM /wrt exception_index. So spend a separate field and
    also save/restore it properly.
    
    Signed-off-by: Jan Kiszka <address@hidden>
    Signed-off-by: Anthony Liguori <address@hidden>

- exception_index/injected, we "could" do same trick that for ide.

commit 1a03675db146dfc760b3b48b3448075189f142cc
Author: Glauber Costa <address@hidden>
Date:   Thu Oct 22 10:26:56 2009 -0200

    v2: properly save kvm system time msr registers

- avi states that a test if the msr has ever used could be used here


commit a0fb002c6462d21ceb9eac8c5772e469ec189374
Author: Jan Kiszka <address@hidden>
Date:   Wed Nov 25 00:33:03 2009 +0100

    kvm: x86: Add support for VCPU event states


I guess no way around for this one.  It could be disabled for non kvm users, 
but that is it.

balloon statistics:

commit 625a5befc2e3200b396594f002218d235e375da5
Author: Adam Litke <address@hidden>
Date:   Tue Jan 26 14:17:35 2010 -0600

    virtio: Add memory statistics reporting to the balloon driver
    

In this case, I don't know what to do (notice that this bit has never been in 
stable and has
been dropped from qemu.git), it was wrong form other reasons.