Hi Andrii,
On 02/08/2019 13:24, Andrii Anisov wrote:
On 02.08.19 12:03, Julien Grall wrote:
A fair amount of leave_hypervisor_tail() deal with the guest itself (i.e vGIC,
P2M...)
All that stuff is what hypervisor does for the guest. And does behind the
guest's back.
Please define "guest's back".
Technically a guest accessing an IO does not know that the access will be
emulated. So this should also take into account as "guest's back".
An hypercall is initiated by the guest directly, so I agree this is not done on
guest's back.
Some of the work done in leave_hypervisor_tail() is an extension of IO
emulation. They are not done directly in the IO emulation because they may take
a long time and get preemption. So I don't see any difference with "IO emulation".
Regarding the vGIC. This is a bit more a grey area. While it is an overhead of
virtualization, this is indirectly initiated by the guest. Indeed, you would
only configure the vGIC if you receive an interrupt generated by one of the
device assigned.
, so I think they should be accounted to the guest time.
This point is arguable. That's why we have a discussion here to agree on the
time accounting approach, what will directly affect scheduling accuracy.
Note the "I think" in my answer. So this is my opinion and your input is
expected.
Cheers,
--
Julien Grall
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