linux-kernel - Re: [PATCH] irqdomain: provide useful debugging information for irq domain

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Message-ID: <1516277158.15644.43.camel@hxt-semitech.com>
Date:   Thu, 18 Jan 2018 12:06:06 +0000
From:   "Yang, Shunyong" <shunyong.yang@...-semitech.com>
To:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "marc.zyngier@....com" <marc.zyngier@....com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Zheng, Joey" <yu.zheng@...-semitech.com>
Subject: Re: [PATCH] irqdomain: provide useful debugging information for irq
 domain

Hi, Marc

On Thu, 2018-01-18 at 08:54 +0000, Marc Zyngier wrote:
> On 18/01/18 01:53, Yang, Shunyong wrote:
> > 
> > Hi, Marc
> > 
> > On Wed, 2018-01-17 at 10:43 +0000, Marc Zyngier wrote:
> > > 
> > > On 17/01/18 10:20, Yang, Shunyong wrote:
> > > > 
> > > > 
> > > > Hi, Thomas and Marc,
> > > > 
> > > > On Wed, 2018-01-17 at 11:01 +0100, Thomas Gleixner wrote:
> > > > > 
> > > > > 
> > > > > On Wed, 17 Jan 2018, Yang, Shunyong wrote:
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > On Wed, 2018-01-17 at 10:33 +0100, Thomas Gleixner wrote:
> > > > > > > 
> > > > > > > 
> > > > > > > 
> > > > > > > And how is that different from:
> > > > > > > 
> > > > > > > > 
> > > > > > > > 
> > > > > > > > 
> > > > > > > > 
> > > > > > > > The nodes under debugfs irq/irqs describes information
> > > > > > > > of
> > > > > > > > every
> > > > > > > > single
> > > > > > > > irq.
> > > > > > > Not at all. It contains the complete hierarchical
> > > > > > > information
> > > > > > > of
> > > > > > > each
> > > > > > > virq.
> > > > > > > 
> > > > > > I think irq_domain_mapping can provide some high-level
> > > > > > information
> > > > > > in a
> > > > > > summary style.
> > > > > > For example, we can check all the IRQs connect to a
> > > > > > specific
> > > > > > irq
> > > > > > chip
> > > > > > or irq domain.
> > > > > You can retrieve the same information from the irq/irqs
> > > > > files.
> > > > > All it
> > > > > takes
> > > > > is a shell script.
> > > > > 
> > > > > Aside of that with hierarchical irq domains the old debug
> > > > > output
> > > > > is
> > > > > just
> > > > > useless.
> > > > > 
> > > > Umm...Agree. Need I post a patch to remove it?
> > > I'm on it.
> > > 
> > In addition to the "%p" to "%px" change in IRQ_DOMAIN_DEBUG you
> > have
> > posted patch to remove it, my original patch includes several other
> > changes:
> > 1. change to "%px" in kasprintf() parameters in
> > function __irq_domain_alloc_fwnode() to build name which reflects
> > the
> > real pointer address from caller, this may be useful when reading
> > debug
> > information.
> >  
> > n = kasprintf(GFP_KERNEL, "irqchip@%px", data);
> Have you investigated whether %pK would work in a debug context?

Although build name with physical address makes it straightforward when
working with tables like MADT. I agree with you about the security
concern. As it's just a name, hashed address is OK.

But it brings new issues. Currently, component like GIC calls this
function with virtual address and ITS with physical address. Is there
possibility that GIC/ITS name is different in each boot? Should we
change GIC/ITS fw handle allocate to name/name-id style?

Thanks
Shunyong