Re: [RFC] GitLab issue tracker labeling process: arch/target, os, and accel labels

[David Gibson]

On Mon, Jun 14, 2021 at 01:32:11PM -0400, John Snow wrote:
> Hi, I'd like to work out our collective preferences for how we triage issues
> that concern the execution environment; namely the arch (now "target", os,
> and accel labels.
> 
> If you're CC'd on this mail, you're either listed as a TCG maintainer, a
> target maintainer, or have been heavily involved in the GitLab issue tracker
> migration process. You might care about how we triage and file these issues.
> 
> I'm sending the mail because I've been (so far) responsible for a lot of the
> labeling as we move over from Launchpad. I'll need to change my process to
> accommodate what our maintainers want to see. (And to encourage others to
> join in on the triage process.)
> 
> As of right now, there's no formal process or document for how we use any of
> the labels -- Thomas and I had been only informally collaborating in our
> usage of them as we migrated from Launchpad. Thomas has a script he uses to
> move the bugs, so I usually don't edit these labels until I give him a heads
> up so I don't break his script.
> 
> Let's discuss what changes we need to make and collaborate on when and how
> we'll make them.

In general, what's the convention when a bug is independent of (say)
the accel: does it get none of the accel tags, or all of them?
Likewise with OS and the other categories.

> # Accel
> 
> Currently "accel: XXX", for HAX, HVF, KVM, TCG, WHPX and Xen.
> 
> https://gitlab.com/qemu-project/qemu/-/labels?subscribed=&search=accel%3A
> 
> Multiple accel labels can be applied to an issue, not just one. The intent
> was to allow for issues that may impact multiple accelerators, though that
> case may be rare.
> 
> I think these are reasonably straightforward and unambiguous, though for
> some qemu-system reports it's not always evident which accelerator applies
> right away without more info. The accel tag is often omitted because of this
> uncertainty.
> 
> I'd like to keep the mapping here 1:1 against ACCEL_CLASS_NAME if I can. It
> makes the mapping from CLI to accel tag fairly straightforward.
> 
> We technically lack a "qtest" accel tag for that parity. It could be added,
> but it's likely not actually useful versus the "tests" label. It's not
> really a user-facing accelerator.
> 
> I see we also have a new "nvmm" accelerator, too, which should now be added
> here.
> 
> RTH raises the issue of the "TCI" subsystem of TCG, which is not a full
> accelerator in its own right, but (I think) a special case of TCG. If I keep
> the 1:1 mapping to ACCEL_CLASS_NAME, "accel: TCI" is inappropriate.
> 
> Some suggestions:
> - "TCI" by itself, simple enough.
> - "TCG-TCI" or "TCG: TCI" or "TCG/TCI" or similar, so that it shows up in
> label search when you search for 'tcg'.
> - "accel: TCG:TCI". Similar to above but uses the "accel:" prefix too.
> 
> My only concern here is completeness of the label: this one seems like it's
> at particular risk of being forgotten or lost. It works perfectly well as an
> organizational bucket for people working on TCI, but I wonder if it will
> work well as an "issue inbox". Intended use begins to matter here. Your
> thoughts, Stefan?
> 
> 
> # OS
> 
> Currently "os: XXX" for BSD, Linux, Windows, and macOS.
> 
> https://gitlab.com/qemu-project/qemu/-/labels?subscribed=&search=os%3A
> 
> Multiple OS labels can be applied to an issue.
> 
> Originally, we kept this label somewhat vague and have been using it to
> identify both the host AND guest involved with an issue.
> 
> Stefan Weil has requested that we refactor this to separate the concerns so
> that he can identify issues where Windows is the host without wading through
> numerous reports where Windows is merely the guest. Reasonable request.
> 
> Shall we split it into "host: XXX" and "guest: XXX" for {BSD, Linux,
> Windows, macOS}?

I think that would be a good idea.  Except maybe "host-os" and
"guest-os", because "host" in particular is ambiguous with host
architecture. (not relevant that often, but sometimes).

> This isn't too hard to do at initial triage time, but we'll need to sift
> through the bugs we've labeled so far and re-label them. Help on this would
> be appreciated. I would prefer we create a *new* set of labels and then draw
> down on the old labels instead of just renaming them. That way, the old
> label can be used as a re-triage queue.

That seems like the right way to do it to me.

> # arch/target
> 
> Currently "target: XXX" for alpha, arm, avr, cris, hexagon, hppa, i386,
> m68k, microblaze, mips, nios2, openrisc, ppc, riscv, rx, s390x, sh4, sparc,
> tricore, xtensa.
> 
> https://gitlab.com/qemu-project/qemu/-/labels?subscribed=&search=target%3A
> 
> The names map 1:1 to the directories in target/.
> The names in [square brackets] in the label descriptions correspond 1:1 with
> the SysEmuTarget QAPI enum defined in qapi/machine.json.
> 
> Multiple target labels can be applied to an issue. Originally, this was
> named "arch", so this was to allow multiple architectures to be specified to
> cover the host/guest environment. If we disentangle this, we may still want
> to allow multiple labels to cover bugs that might affect multiple targets,
> though that case might be rare.

Agreed.  I think mixing host and guest properties together is a bad
idea.  These are relatively rarely related to each other.
Bugs affecting multiple, but not all targets are uncommon, but not
super rare (mostly due to chunks of code shared across several target
archs, like ACPI and device tree).

> Recently, we renamed this from "arch: XXX" to "target: XXX", though the
> label had been being used for both the host and guest architecture, so this
> will need to be re-audited to remove cases where the label had been applied
> for the host architecture.

Oops.

> We probably want to keep a set of labels that apply to the host
> architecture. These are useful for build failures, environment setup issues,
> or just documenting the exact environment on which an issue was observed.

Ah.. that's another general question.  Are the labels supposed to
document where the problem has been definitely observed, or a best
estimate at where it will appear.  It would be very common for a bug
to be observed initially on only one, but quickly turn out to be
independent of host and/or target arch.

> We won't likely require the full set of targets to be duplicated for this
> purpose: possibly just the most common ones. I assume those are:
> 
> arm, i386, ppc, s390x
> 
> How should we tag those? "host-arch: XXX"?
> 
> What I would like to avoid is creating labels like "host: windows-i386"
> where the cross matrix of ({host,guest} X OS x ARCH) starts to require
> ever-increasing specificity of initial triage labels and may increase the
> risk of overly-specified bugs going unnoticed. Maybe my concern is
> unfounded, but I think the over-specificity will hurt more than help at this
> stage.
> 
> 
> # Current Plan
> 
> - Add "accel: NVVM" label
> - Don't add "accel: qtest".
> - Add "host: {Windows, BSD, Linux, macOS}" and "guest: {Windows, BSD, Linux,
> macOS}" labels.

Again, I suggest "host-os" and "guest-os"

> - Migrate "os: XXX" labels to the above split. Help wanted.
> - Remove the "os: XXX" labels when the above is done.
> - Re-audit "target: XXX" labels and remove usages that applied to the host
> instead of the guest. Help wanted. Possibly assign new host-arch labels.
> - Create a document in /docs/devel/gitlab-process.rst based on the outcome
> of this thread to formalize our decisions and reasonings. Future patches to
> this doc can serve as the discussion point for changing that process. There
> are other topics to discuss beyond these labels as well, but these three
> topics felt like the most pressing to address given where we are in our
> Launchpad migration process.
> 
> 
> Less sure:
> 
> - Create host-arch: XXX labels (Unsure of name, which platforms are
>   important to track? see above.)

Maybe leave and see if looks like it would be useful?

> - Create "TCG: TCI" label (Unsure of naming)
> 
> 
> Thanks,
> --js
> 

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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