Re: [PATCH v3 6/8] admin: Add theory of operation for write recording commands

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Nov 16, 2023 at 05:29:54AM +0000, Parav Pandit wrote:
> We should expose a limit of the device in the proposed WRITE_RECORD_CAP_QUERY command, that how much range it can track.
> So that future provisioning framework can use it.
> 
> I will cover this in v5 early next week.

I do worry about how this can even work though. If you want a generic 
device you do not get to dictate how much memory VM has.

Aren't we talking bit per page? With 1TByte of memory to track ->
256Gbit -> 32Gbit -> 8Gbyte per VF?

And you happily say "we'll address this in the future" while at the same
time fighting tooth and nail against adding single bit status registers
because scalability?


I have a feeling doing this completely theoretical like this is problematic.
Maybe you have it all laid out neatly in your head but I suspect
not all of TC can picture it clearly enough based just on spec text.

We do sometimes ask for POC implementation in linux / qemu to
demonstrate how things work before merging code. We skipped this
for admin things so far but I think it's a good idea to start doing
it here.

What makes me pause a bit before saying please do a PoC is
all the opposition that seems to exist to even using admin
commands in the 1st place. I think once we finally stop
arguing about whether to use admin commands at all then
a PoC will be needed before merging.


-- 
MST