[Qemu-devel] [PATCH 0/5] migration: support migration with image files

[Anthony Liguori]

This series allows live migration to work with image formats.  This series has
two parts.  The first part adds a new error infrastructure to migration which
allows for different subsystems (other than qdev) to block migration when
specific features are in use.

The second part adds block interfaces to flush metadata with image formats.

The migration error infrastructure is a no brainer for 1.0.  It significantly
improves the user experience and prevents a user from doing things that will
cause a VM to crash during migration.

I'm less comfortable with the block interface for flushing metadata for 1.0.
The code is completely isolated to the image formats and live migration.  It
should have no impact on normal use of an image format or live migration with
raw images.  That makes the risk for this very, very low.

Moreover, I'm sympathetic to the argument that this is a required feature for a
1.0 release.  Image formats are a fairly normal way to use QEMU and not
supporting live migration in this scenario means that live migration won't work
for a large portion of QEMU's users.