Re: [Linaro-open-discussions] Notes on Linaro Open Discussions meeting 4 Nov 2020 - Linaro-open-discussions - op-lists.linaro.org

26 Nov 2020


      On Thu, Nov 26, 2020 at 8:47 AM Jonathan Cameron <
jonathan.cameron@huawei.com> wrote:
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Hi Mike,
lushenming is happy to present / discuss the topic Lorenzo requested.
https://lore.kernel.org/linux-arm-kernel/20201123065410.1915-1-lushenming@hu...
For agenda list please add “VLPI Migration support on Gic V4.1”
Lorenzo also mentioned he had an update on
“Use of BDF to identify PCI devices in ACPI tables”
which I’d definitely like to be on the agenda.
Final topic that has been discussed for inclusion is
“vCPU hotplug”
Let’s move that up to confirmed topics.
It’s going to be a full agenda, so I suggest we try to share slides in
advance and we keep
to a fairly tight schedule!
For those doing slides, I assume best approach is email them to you Mike
and you upload
them to the collaborate page?  Perhaps if people could also let Mike know
expected time
needed (always a guess) then we can decide to spill some topics to a
future meeting or
email discussion if necessary.
Perfect, I will add the topics and slides
...
Thanks,
Jonathan
*From:* Mike Holmes [mailto:mike.holmes@linaro.org]
*Sent:* 26 November 2020 07:28
*To:* Jonathan Cameron jonathan.cameron@huawei.com
*Cc:* Lorenzo Pieralisi lorenzo.pieralisi@arm.com;
linaro-open-discussions@op-lists.linaro.org
*Subject:* Re: [Linaro-open-discussions] Notes on Linaro Open Discussions
meeting 4 Nov 2020
I see a lot of new subscriptions to the list - welcome.
Here is the updated meeting slot poll for the week of December 7th to
December 12th
https://doodle.com/poll/sgy9esiim4rapitz?utm_source=poll&utm_medium=link
Agenda
https://collaborate.linaro.org/display/LOD/Linaro+Open+Discussions+Home
On Wed, Nov 25, 2020 at 4:14 PM Jonathan Cameron <
Jonathan.Cameron@huawei.com> wrote:
On Wed, 25 Nov 2020 16:05:51 +0000
Mike Holmes mike.holmes@linaro.org wrote:
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On Wed, Nov 25, 2020 at 4:01 PM Lorenzo Pieralisi via
Linaro-open-discussions linaro-open-discussions@op-lists.linaro.org
wrote:
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On Wed, Nov 25, 2020 at 03:22:19PM +0000, Jonathan Cameron wrote:
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On Wed, 25 Nov 2020 13:58:38 +0000
Lorenzo Pieralisi lorenzo.pieralisi@arm.com wrote:
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On Wed, Nov 25, 2020 at 12:51:49PM +0000, Jonathan Cameron wrote:
[...]
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> Is December 2nd confirmed as next session ? If possible 3PM
GMT
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works
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> better for me; the NUMA topic raised by Jonathan is another
interesting
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> topic for debate.
Just to check, which NUMA topic?
https://op-lists.linaro.org/pipermail/linaro-open-discussions/2020-November/...
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It would be useful (for me certainly) if you can give an update on
what's still pending in the items in the discussion above (eg it is
not clear what the "PCI fix" is) + how it is linked to CXL.
Sure, that should be a fairly short topic, but I'm happy to try to
fill
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in the gaps.
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@Mike, can you add "Generic initiators - pending items" to the
agenda.
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For the PCI 'fix'  it is this one that got applied and then reverted
in
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4.20 timeframe
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http://patchwork.ozlabs.org/project/linux-pci/patch/20180912152140.3676-2-Jo...
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I've not rebased or tested it recently so I'll check that it still
appears to be right
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before the call.
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The vCPU hotplug is also worth adding (even though I do not know
what
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was discussed at KVM forum).
I was just about to email about that one.  From our side, all that
is
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currently
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going on around vCPU Hotplug is a rebase.   At KVM forum Mark R
kindly
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offered
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to see if he could find out answers to a few open questions.
Perhaps
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catch
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up with Mark, or see if he can make the call?
Ok, will catch up with him, it is probably better if I have some time
to do it (ie postpone the call for a week).
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Furthermore, I am keen on discussing this:
https://lore.kernel.org/linux-arm-kernel/20201123065410.1915-1-lushenming@hu...
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if the submitters are available, it would help to get some context
in
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relation to upstream discussions.
I've messaged lushenming so hopefully we can sort out something on
that
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front.
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Looks like finding a time next week is proving challenging.  If that
fails, perhaps we should try for the week after?
Yes we can, it would be easier to prepare the topics and find a
suitable
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day as well, next week it looks like it is challenging. It would also
give us some time to extend the invite.
Please let me know and apologies to Mike for all these emails to get it
organized.
No problem, as soon as it is confirmed we want to try for the following
week I can set up a poll to pick the day and hour
Definitely sounds like a better plan. Fingers crossed people have slightly
more open schedules that week!
Thanks for sorting this out Mike.
Jonathan
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Thanks,
Lorenzo
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Thanks,
Jonathan
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Thanks !
Lorenzo
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I've lost track of what we are talking about.
> Other than that we can slot in the topics that
> weren't discussed last time:
>
>
https://collaborate.linaro.org/display/LOD/Linaro+Open+Discussions+Home
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>
> even though those require a bit of preparation so the sooner
we
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finalize
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> the schedule the better.
Seems we have clashed with some internal Huawei activities so
some
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people who
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would normally be active are snowed under this week.
Jonathan
>
> Please let me know, thanks.
>
> Lorenzo
>
> > * DT alignment. Don't want different solutions for each
firmware
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type.
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> > * Lorenzo / Sami to check IORT revision E is final.
> >
> > SVA
> > ===
> >
> > Zangfei gave summary:
> >  - Huawei has devices that are not PCIe but are presented
as
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such.
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> >  - They support stall mode for SVA (spec violation)
> >  - Resistance from kernel maintainers to maintaining a
white
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list for any quirk. Fine to fix
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> >    it once (JPB), but not to keep doing so.
> >  - Note that stall mode not yet supported at all (JPB to
send
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out this cycle).
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> >  - If longer term fix need add can't be done via PCISIG etc
then
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need to convince
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> >    PCI and SMMU maintainers.   Noted that quirk is very
little
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code.
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> >
> > * Other SVA topics.
> >   - Mentioned virtual SVA (no actually problems just
expressing
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interest!)
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> >   - Would need Eric Auger, wasn't on topic list so Eric not
on
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call.
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> >
> > AI: Nothing planned until after JPB has upstreamed stall
mode.
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Hard to have discussion before that.
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> >
> > DVFS
> > ====
> >
> > guohanjun
> >
> > Solutions exist for
> > * CPU DVFS (voltage + frequency scaling)
> > * PCIe device power states etc
> >
> > No standard way of controlling Uncore voltage and frequency
for
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ACPI based systems.
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> >
> > 3 options:
> > 1. MMIO / kernel driver.
> > 2. PSCI via trusted firmware and system management
controller.
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> > 3. ACPI (wrapping up an op region and SCMI)
> >
> > Clarifications / discussions.
> >  * Vincent G: Power states, or voltage frequency of
interest?
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Ans Voltage Freq
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> >  * Considered SCMI?  Ans: Works only for DT as SCMI under
ACPI
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is wrapped up in AML
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> >    so looks like an ACPI interface.
> >  * Sudeep H: Necessary to trace CPU freq?  Yes.
> >  * Sudeep H: Why not do it in firmware entirely?  Ans. Not
just
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CPU.  For example PCI device accessing
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> >    memory may well need the ring bus to be fast.
> >  * Vincent G: Bandwidth affected?  Yes. VG: mobile does this
by
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specifying a BW requirement (via SCMI.-
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> >  * Sudeep H Observed need to expose it via ACPI spec.
(option 3
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above).
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> >  * Sudeep H: Does PCI also need fine-grain control? We
might
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need to add to the spec.
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> >  * Sudeep H:  What are the requirements? gaohanjun: Now we
just
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frequency scaling.
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> >  * Jonathan C: Noted PCI power state is not enough.  It's
workload dependent.
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> >  * Sudeep H: We need to gather all the info, need to talk
in
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ASWG about DVFS
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> >  * Jonathan C:  For now direct control probably makes
sense.
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Whilst it would be nice to have
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> >    a detailed enough system description in a standard way
to
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make general software that is a
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> >    big spec job.
> >  * Jonathan C: Seems like true standard SW will not happen
any
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time soon.
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> >
> > AI: RFC to the linux-pm / linux-acpi Rafael and those in
this
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discussion to ask about
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> >     interest in adding per device DVFS to ACPI spec.
Possibly
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pursue code first ACPI
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> >     approach.
> >
> > If I've miss listed or "volunteered" anyone for AIs they
didn't
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agree to then please
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> > correct that.
> >
> > Thanks all for contributions. I for one found it a very
useful
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call!
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> >
> > Jonathan
> >
> >
> > --
> > Linaro-open-discussions mailing list
> >
https://collaborate.linaro.org/display/LOD/Linaro+Open+Discussions+Home
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> >
https://op-lists.linaro.org/mailman/listinfo/linaro-open-discussions
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--
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...
...
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--
*Mike Holmes* | Director, Foundation Technologies, Linaro
Mike.Holmes@linaro.org mike.holmes@linaro.org
"Work should be fun and collaborative, the rest follows"
-- 
Mike Holmes | Director, Foundation Technologies, Linaro
Mike.Holmes@linaro.org mike.holmes@linaro.org
 "Work should be fun and collaborative, the rest follows"