On 03/13/2012 05:47 AM, Avi Kivity wrote:
On 03/13/2012 11:18 AM, Daniel P. Berrange wrote:
On Mon, Mar 12, 2012 at 12:33:33PM +0200, Avi Kivity wrote:
On 03/12/2012 11:04 AM, Wen Congyang wrote:
Do you have any other comments about this patch?
Not really, but I'm not 100% convinced the patch is worthwhile. It's
likely to only be used by Linux, which has kexec facilities, and you can
put talk to management via virtio-serial and describe the crash in more
details than a simple hypercall.
As mentioned before, I don't think virtio-serial is a good fit for this.
We want something that is simple& guaranteed always available. Using
virtio-serial requires significant setup work on both the host and guest.
So what? It needs to be done anyway for the guest agent.
Many management application won't know to make a vioserial device available
to all guests they create.
Then they won't know to deal with the panic event either.
Most administrators won't even configure kexec,
let alone virtio serial on top of it.
It should be done by the OS vendor, not the individual admin.
The hypercall requires zero host
side config, and zero guest side config, which IMHO is what we need for
this feature.
If it was this one feature, yes. But we keep getting more and more
features like that and we bloat the hypervisor. There's a reason we
have a host-to-guest channel, we should use it.
The problem is that virtio-serial sucks for something like this.
We have two options I think:
1) We could reserve a portion of the hypercall space to be deferred to userspace
for stuff like this.
2) We could invent a new hypercall like facility that was less bloated than
virtio-serial for stuff like this using MMIO/PIO.
Regards,
Anthony Liguori
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