Re: [libvirt] [Qemu-devel] live snapshot wiki updated
On 07/20/11 12:28, Daniel P. Berrange wrote:
On Wed, Jul 20, 2011 at 12:15:02PM +0200, Nicolas Sebrecht wrote:
> Actually, libvirt should not have to worry if the filename provided by
> QEMU is valid. I think it should trust QEMU. If QEMU doesn't provide
> information others can trust; it should be fixed at QEMU side.
The security goal of libvirt is to protect the host from a compromised
QEMU, therefore QEMU is, by definition, untrusted.
Well that part goes both ways. By applying this model you are going to
make it a hard requirement for libvirt to be upgraded with QEMU even for
smaller updates.
>> We're not fighting over the internals of metadata. We
just need to know
>> ahead of launching QEMU, what backing files an image has & what format
>> they are in. We do that by reading at the metadata headers of the disk
>> images. We never attempt to write to the disk images. Either someone
>> provides a library todo that, or we write the probing code for each
>> file format in libvirt. Currently we have the latter.
>
> This is what I would call "fighting with QEMU internals". How do you
> prevent from concurrency access and modifications? Ideally speacking
> libvirt should be able to co-exist with foreign implementations, all
> requesting QEMU.
QEMU is *not* yet running at the time libvirt reads the file metadata.
Of course it is: hotplug
Jes