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#openstack-nova - 2019-06-11
16:04:05 efried if I care that it's SEV, I specify the SEV trait and land on an AMD host
16:04:05 efried if the image/flavor prop is specified, it means I want mem encryption
16:04:21 aspiers Sure, but I'm talking about the last case
16:04:35 aspiers In that case, there needs to be logic *somewhere* in the code which says "OK, the user wants encrypted memory, and the only way to achieve that currently is SEV"
16:04:47 aspiers so that it triggers usage of all the SEV bits
16:04:52 efried I never land on a non-capable host, because only capable hosts have MEM_ENCRYPTION_CONTEXT inventory.
16:04:52 efried No.
16:05:13 efried Today the only hosts exposing that inventory will be SEV-capable hosts, so that falls into place.
16:05:15 aspiers Sure
16:05:22 aspiers but where does that logic go? ^^^
16:05:40 efried It's implicit. It's free. It doesn't "go" anywhere.
16:05:45 aspiers It's not enough to land on the right host
16:05:55 aspiers nova needs to know to add all the extra bits to the guest config
16:06:11 efried extra bits
16:06:21 aspiers yes, like <launchSecurity /> and <locked />
16:06:28 efried always the same if I'm SEV, right?
16:06:28 aspiers and a whole bunch of iommu stuff
16:07:13 aspiers Not sure I understand the question
16:07:28 aspiers That extra config varies depending on a whole bunch of things
16:07:45 efried okay, but the virt driver knows how to twiddle the guest config based on a) mem_encryption flavor/image prop, and b) fact I'm on an AMD host
16:08:21 efried If there are user-/admin-configurable options beyond "yes" or "no", we should talk about where those should go.
16:08:33 efried But my understanding was that from the admin/user pov it was "yes" or "no".
16:08:39 aspiers It is
16:08:52 efried and if there are any variations, it's discovered based on specifics of the system
16:08:53 efried okay
16:08:59 efried so the virt driver knows b)
16:09:04 efried that's how it knows it's doing SEV
16:09:20 aspiers It sounds like you are saying that the logic should go in the virt driver and it should be "if the current context has MEM_ENCRYPTION_CONTEXT=1 and the current host is SEV, then add the SEV bits"
16:09:50 efried okay, yes
16:10:06 aspiers OK, thanks - think I know how to write it now
16:10:51 efried I suppose if you're being careful, you should raise a nice exception if you get MEM_ENCRYPTION_CONTEXT without being SEV-capable (regardless of AMD-ness)
16:11:17 aspiers Yes can do. BTW SEV is AMD-only
16:11:29 aspiers Very much a vendor-specific thing
16:12:00 aspiers You probably knew that and I'm just misinterpreting the point of your last clause in parentheses
16:14:51 efried Yes, what I'm saying is, theoretically there should have been no way you got this far if the host wasn't SEV-capable, but, I don't know, if someone switched off the capability between allocation and spawn, you should fail hard.
16:15:37 aspiers Yep, absolutely
16:15:50 aspiers It was the "(regardless of AMD-ness)" bit I didn't quite get
16:15:57 efried stephenfin: fixes it py27
16:16:07 stephenfin sweet
16:16:18 stephenfin I'll submit that as a fix to pycodestyle
16:17:59 efried stephenfin: fixes in py36 as well
16:18:13 efried stephenfin: why is self.lines[-1] correct?
16:19:38 stephenfin It's not, actually, now that you mention it
16:21:11 stephenfin Or maybe it is. Needs more tests
16:21:34 aspiers efried: bbobrov is on vacation so I'm taking over his SEV patches, and thinking about rebasing them all into a single linear commit series (even though this won't accurately reflect the dependencies between them) - does that make sense?
16:22:03 efried aspiers: Yes it does. I was kind of wondering why they weren't already in one line.
16:23:04 aspiers efried: Well, I gave a few reasons for that in our previous discussions on this, but an additional reason is weak coordination between me and him ... :)
16:23:18 efried ack
16:23:38 aspiers One downside is that if an earlier patch fails CI, it bottlenecks merging of anything higher up
16:24:11 aspiers but if it makes life easier for reviewers then that probably overrules any other considerations
16:24:48 efried It's not just that. It's that ultimately you're going to need a patch that ties everything together. And as previously discussed, you can't have a dep tree that's upside down.
16:24:56 aspiers Sure
16:25:03 aspiers Another downside is that it will significantly increase the number of rebases
16:25:10 aspiers but again I can live with those
16:25:10 efried So yes, the fact that some patches *could* be merged independently if they were separated - it's just something that we live with.
16:25:33 aspiers Definitely a nice future enhancement for Gerrit
16:25:39 aspiers One can dream ...
16:26:29 aspiers I guess I'll rebase all his stuff on top of mine, since it's the next phase
16:26:57 aspiers My stuff is all about feature detection and scheduling; his is about guest config and booting
16:27:17 aspiers Then the series will roughly match the order of work items
16:27:31 aspiers as listed http://specs.openstack.org/openstack/nova-specs/specs/train/approved/amd-sev-libvirt-support.html#work-items
16:29:46 efried So your check in the virt driver should just reuse the same "am I SEV capable" method that it used to expose the MEM_ENCRYPTION_CONTEXT inventory and the HW_CPU_X86_AMD_SEV trait in the first place. Which is why there should be no way for that check to fail - unless something changed in between update_provider_tree and spawn.
16:29:46 efried I just meant "being on AMD isn't enough; other stars must align for SEV to be supported"
16:29:46 efried > It was the "(regardless of AMD-ness)" bit I didn't quite get
16:29:46 efried aspiers:
16:31:06 efried and yes, I agree with your ordering, especially since your patches are already 2/3 with one +2 and the last one very close to same, but the other ones are still awaiting your nod before I even dig into them.
16:37:27 aspiers efried: OK thanks, we're 100% aligned :)
16:40:26 aspiers efried: Oh, one extra detail regarding the above - yes the check can just look at the supports_amd_sev instance variable, but it also needs to check extra_specs for resources:MEM_ENCRYPTION_CONTEXT=1 to know that encrypted memory was requested, right?
16:40:43 aspiers If *both* are true then it should add all the SEV guest config tweaks
16:42:10 efried s/check extra_specs/check the allocation/ but otherwise, ja, genau
16:44:11 openstackgerrit Lee Yarwood proposed openstack/nova master: libvirt: flatten rbd images when unshelving an instance https://review.opendev.org/457886
16:49:06 aspiers efried: OK thanks, I guess that will become self-evident when I look into how to check allocations
16:49:51 efried aspiers: Well, I would rather you check the allocations rather than duplicating the logic you just put in your request filter to check and validate the flavor & image
16:50:12 efried The allocations are passed to spawn. They're just a dict. See the placement API reference for the format.
16:50:26 aspiers Cool, thanks!
16:50:54 aspiers I'm beginning to feel that this is nearing code-completion and maybe can be added to the runway queue soon
16:51:00 efried yup
16:51:15 aspiers I do want to test the whole series on real SEV hardware first though
16:51:48 aspiers (which I have available to me right now)
16:58:05 efried dustinc: sdk release 0.31.0 is in u-c now, so I'd like to respin the series to bump that and fix up that other thing we talked about yesterday. Let me know when you're clear of local edits.
17:44:22 dustinc efried: Hmm...might be a bit, go for it and I can deal with merging my local edits
18:03:16 spatel sean-k-mooney: any idea about this setting https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1724614 ?
18:03:17 openstack Launchpad bug 1724614 in linux (Ubuntu) "[KVM] Lower the default for halt_poll_ns to 200000 ns" [Medium,Triaged]
18:03:59 spatel i have default value but i heard it gives good boost to CPU if you play with this setting
18:05:24 mriedem efried: do we have a bug for the test_check_doubled_words py27 failures?
18:09:41 sean-k-mooney spatel: i have not had experience with tweaking that specific tunable in the past.
18:10:35 spatel even i am running in default, i heard from someone but may be its application specific.
18:10:43 sean-k-mooney spatel: i would proably try to find some infomation on it form nfv/hpc tuning guide but there are man paramaters that can be tweaked not all of which will help for all workloads
18:11:01 spatel +1
18:11:53 spatel but i am seeing sometime my ksm cpu usage going high on compute node
18:12:10 spatel [ksmd]
18:12:29 sean-k-mooney you proably want to read this https://www.kernel.org/doc/Documentation/virtual/kvm/halt-polling.txt
18:17:56 sean-k-mooney spatel: ibm seam to be recommendign a value fo 80000 ns based on https://www.ibm.com/support/knowledgecenter/en/linuxonibm/liaag/wkvm/wkvm_c_tune_kvm.htm but this seams to be a tradeoff between powersavings and latency which translated to higher throughput at the cost of cpu efficenty
18:19:51 spatel it seem that setting will schedule in very less time which increase power usage
18:20:29 spatel anyway i am not going to change until i have solid reason to do
18:37:06 mriedem coreycb: is this the right change log to be looking at for ubuntu bionic py27? http://changelogs.ubuntu.com/changelogs/pool/main/p/python2.7/python2.7_2.7.15~rc1-1ubuntu0.1/changelog
18:38:34 mriedem efried: https://bugs.launchpad.net/nova/+bug/1832392
18:38:35 openstack Launchpad bug 1832392 in OpenStack Compute (nova) "nova.tests.unit.test_hacking.HackingTestCase.test_check_doubled_words failing in py27 jobs since June 10" [High,Confirmed]
18:40:04 efried mriedem: Tracking it against bug/1804062
18:40:16 efried mriedem: https://review.opendev.org/664622 is merging to disable the test

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