On Tue, Nov 24, 2009 at 12:39:50PM +0200, Dor Laor wrote: > On 11/23/2009 02:15 PM, Juan Quintela wrote: >> Dor Laor<dl...@redhat.com> wrote: >>> > In the last couple of days we discovered some issues regarding stable >>> > ABI and the robustness of the live migration protocol. Let's just jump >>> > right into it, ordered by complexity: >>> > >>> > 1. Control*every* feature exposed to the guest by qemu cmdline: >>> > >>> > While thinking on cross version migration, and reviewing some >>> > patches, I noticed that there are many times that we use feature bits >>> > in order to expose functionality for the guest driver - example: >>> > VIRTIO_BLK_F_BARRIER, but we do not control it from qemu cmdline. >> In my opinion this is madness, qemu command line is already too >> complicated. I agree with anthony to put it in the command line. > > Qemu's cmdline is currently our config file.. Actually there is nothing > wrong with it. Human users shouldn't be interested with these changes > and management software should not have problem manipulating it. > We do need flexibility of controlling our features like any other > software component. > >> I will go further, and think that this kind of issues should be put into >> the machine type. >> >> If you start qemu with -M pc-0.10, it should save the state in a 0.10 >> compatible way (that don't happens at the moment, but it should work >> that way). > > That's the idea - to keep it part of qdev and by default use it with -M.
I think we want to keep these things separate: machine description should be for things that are both guest visible and not changeable by guest, so it absolutely must stay constant as long as guest it alive. -- MST
