On Tue, 13 Aug 2019 11:15:34 +0200, Paolo Bonzini <[email protected]> wrote:
> On 09/08/19 17:59, Adalbert Lazăr wrote:
> > +If `now` is 1, the command reply is enabled/disabled (according to
> > +`enable`) starting with the current command. For example, `enable=0`
> > +and `now=1` means that the reply is disabled for this command too,
> > +while `enable=0` and `now=0` means that a reply will be send for this
> > +command, but not for the next ones (until enabled back with another
> > +*KVMI_CONTROL_CMD_RESPONSE*).
> > +
> > +This command is used by the introspection tool to disable the replies
> > +for commands returning an error code only (eg. *KVMI_SET_REGISTERS*)
> > +when an error is less likely to happen. For example, the following
> > +commands can be used to reply to an event with a single `write()` call:
> > +
> > + KVMI_CONTROL_CMD_RESPONSE enable=0 now=1
> > + KVMI_SET_REGISTERS vcpu=N
> > + KVMI_EVENT_REPLY vcpu=N
> > + KVMI_CONTROL_CMD_RESPONSE enable=1 now=0
>
> I don't understand the usage. Is there any case where you want now == 1
> actually? Can you just say that KVMI_CONTROL_CMD_RESPONSE never has a
> reply, or to make now==enable?
The enable=1 now=1 is for pause VM:
KVMI_CONTROL_CMD_RESPONSE enable=0 now=1
KVMI_PAUSE_VCPU 0
KVMI_PAUSE_VCPU 1
...
KVMI_CONTROL_CMD_RESPONSE enable=1 now=1
We wait for a reply to make sure the vCPUs were stopped without waiting
for their pause events.
We can get around from userspace, if you like:
KVMI_CONTROL_CMD_RESPONSE enable=0 now=1
KVMI_PAUSE_VCPU 0
KVMI_PAUSE_VCPU 1
...
KVMI_PAUSE_VCPU N-2
KVMI_CONTROL_CMD_RESPONSE enable=1 now=0
KVMI_PAUSE_VCPU N-1
>
> > + if (err)
> > + kvmi_warn(ikvm, "Error code %d discarded for message id %d\n",
> > + err, msg->id);
> > +
>
> Would it make sense to even close the socket if there is an error?
>
> Paolo
Sure.
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