Re: [Xen-devel] [PATCH 39/57] ARM: new VGIC: Add ACTIVE registers handlers

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 13/03/18 17:34, Andre Przywara wrote:
> On 13/03/18 17:14, Julien Grall wrote:
> > On 13/03/18 17:02, Andre Przywara wrote:
> > > On 08/03/18 15:39, Julien Grall wrote:
> > > > On 05/03/18 16:03, Andre Przywara wrote:
> > I can't see how a knowledgeable admin will be able to know that IRQ 2 is
> > active with just the register value.
> Well, I was assuming that a really knowledgeable admin would somehow
> forward the error message either to the ML or at least to $search_engine.
> ...
Surely, but it does not mean the message should be clueless for the 
developer. I would rather no spent 10 min to try to find out what's 
going on where reading logs...
> > > Does that sound OK?
> > I would still prefer the one per IRQ and using printk(XENLOG_G_*).
> I really don't think one per IRQ is too useful. A developer however can
> easily deal with "IRQ45, value: 0x00802000" from a log. And can deduce
> from there that it's about IRQ45 and IRQ55. Following the example above
> you would either see one "IRQ32, value: 0xffffffff" or "IRQ 45, value:
> 0x00002000".
I still can't see how the developer would know the IRQ55 is active or 
not. That's the whole purpose of the per IRQ.
> That looks like a good compromise between readability (having the IRQ
> number for admins) and brevity.
You may save 10 characters on the logs, you likely going to waste 10 min 
of the developer to understand what that messages really mean.
> I changed it now to output:
> %pv: vGICD: clearing active state not supported (IRQ%u, value: 0x%08lx)
>
> > I don't much care about the spam, see why above.
> Having them on the console between Dom0 messages is really scary, but
> not helpful if it's *more* than one. Since it's a known limitation of
> the VGIC emulation, not a real "error" in that sense.
It is the same as having any Xen messages interleaved with Dom0 
messages. If the user is not happy with that, then it can divert Dom0 
console to another UART.
Cheers,

--
Julien Grall

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