Re: [PATCH v2 14/17] kvm: x86: Introduce kvmclock device to save/restore its state

Glauber Costa
2011-01-03T16:37:47Z

On Mon, 2011-01-03 at 09:33 +0100, Jan Kiszka wrote:
> From: Jan Kiszka <jan.kiszka@siemens.com>
>
> If kvmclock is used, which implies the kernel supports it, register a
> kvmclock device with the sysbus. Its main purpose is to save and restore
> the kernel state on migration, but this will also allow to visualize it
> one day.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> CC: Glauber Costa <glommer@redhat.com>

Hi Jan.

I've just recently posted a patch (not sure what was made from it), that
fixes a bug that you reintroduce here.

The bug is: if we call KVM_GET_CLOCK ioctl in pre_save, this means that
this value will change every time we issue savevm, even if the machine
is not run in between.

Ideally, we'd like to have two consecutive savevms returning the exact
same thing in that situation.

I like the general approach of moving it to sysbus, but please move the
ioctl to change state notifiers.

Cheers!