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SubjectRe: [PATCH] iommu: Lower severity of add/remove device messages
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On Fri, 2020-03-27 at 18:04 +0000, Robin Murphy wrote:
> On 2020-03-27 1:02 pm, Ezequiel Garcia wrote:
> > Hello Joerg,
> >
> > Thanks for reviewing.
> >
> > I understand this change bears some controversy
> > for IOMMU, as developers are probably used to see these
> > messages.
> >
> > On Fri, 2020-03-27 at 10:50 +0100, Joerg Roedel wrote:
> > > On Mon, Mar 23, 2020 at 06:49:56PM -0300, Ezequiel Garcia wrote:
> > > > These user messages are not really informational,
> > > > but mostly of debug nature. Lower their severity.
> > >
> > > Like most other messages in the kernel log, that is not a reason to
> > > lower the severity.
> > >
> > > These messages are the first thing to look at when
> > > looking into IOMMU related issues.
> > >
> >
> > Sure, but the messages are still here, you can
> > always enable them when you are looking at IOMMU issues :-)
>
> That still begs the question of who "you" is and how they know they're
> debugging an IOMMU issue in the first place. When all the developer has
> to go on is a third-hand bugzilla attachment from a distro user's vague
> report of graphics corruption/poor I/O performance/boot
> failure/whatever, being able to tell straight away from a standard dmesg
> dump whether an IOMMU is even in the picture or not saves a lot of
> protracted back-and-forth for everyone involved.
> > The idea is to reduce the amount of verbosity in the kernel.
>
> Under what justification? Users with slow consoles or who just want a
> quiet boot are already free to turn down the loglevel; a handful of
> messages at boot-time and device hotplug seem hardly at risk of drowning
> out all the systemd audit spam anyway. Note that the IOMMU subsystem is
> by nature a little atypical as a lot of what it does is only visible as
> secondary effects on other drivers and subsystems, without their
> explicit involvement or knowledge. In that respect, hiding its activity
> can arguably lead to more non-obvious situations than many other subsystems.
>
> > If all subsystems would print messages that are useful
> > when looking at issues, things would be quite nasty verbose.
>
> From a personal standpoint, can we at least eradicate all the "Hi! I'm
> a driver/subsystem you don't even have the hardware for!" messages
> first, then maybe come back and reconsider the ones that convey actual
> information later?
>

Do we really still have those???

Thanks,
Ezequiel

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