On 03/22/2010 12:34 PM, Ingo Molnar wrote:
This is really just the much-discredited microkernel approach for keeping
global enumeration data that should be kept by the kernel ...
Lets look at the ${HOME}/.qemu/qmp/ enumeration method suggested by Anthony.
There's numerous ways that this can break:
- Those special files can get corrupted, mis-setup, get out of sync, or can
be hard to discover.
- The ${HOME}/.qemu/qmp/ solution suggested by Anthony has a very obvious
design flaw: it is per user. When i'm root i'd like to query _all_ current
guest images, not just the ones started by root. A system might not even
have a notion of '${HOME}'.
- Apps might start KVM vcpu instances without adhering to the
${HOME}/.qemu/qmp/ access method.
- There is no guarantee for the Qemu process to reply to a request - while
the kernel can always guarantee an enumeration result. I dont want 'perf
kvm' to hang or misbehave just because Qemu has hung.
If your position basically boils down to, we can't trust userspace and
we can always trust the kernel, I want to eliminate any userspace path,
then I can't really help you out.
I believe we can come up with an infrastructure that satisfies your
actual requirements within qemu but if you're also insisting upon the
above implementation detail then there's nothing I can do.
Regards,
Anthony Liguori
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