From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [Patch V3 19/37] x86, irq: introduce mechanisms to support
 dynamically allocate IRQ for IOAPIC
Date: Wed, 28 May 2014 23:22:06 +0200 (CEST)
Message-ID: <alpine.DEB.2.10.1405282320430.3952@nanos>
References: <1401178092-1228-1-git-send-email-jiang.liu@linux.intel.com> <1401178092-1228-20-git-send-email-jiang.liu@linux.intel.com> <alpine.DEB.2.02.1405271445050.21720@ionos.tec.linutronix.de> <53856D8E.3010401@linux.intel.com>
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To: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>, Grant Likely <grant.likely@linaro.org>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, "Rafael J. Wysocki" <rjw@rjwysocki.net>, Bjorn Helgaas <bhelgaas@google.com>, Randy Dunlap <rdunlap@infradead.org>, Yinghai Lu <yinghai@kernel.org>, x86@kernel.org, Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Andrew Morton <akpm@linux-foundation.org>, Tony Luck <tony.luck@intel.com>, Joerg Roedel <joro@8bytes.org>, Paul Gortmaker <paul.gortmaker@windriver.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-acpi@vger.kernel.org, Ingo Molnar <mingo@kernel.org>, linux-pm@vger.kernel.org
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On Wed, 28 May 2014, Thomas Gleixner wrote:
> On Wed, 28 May 2014, Jiang Liu wrote:
> > This is used to work around special non-ISA interrupts with GSI below
> > NR_IRQS_LEGACY. The original code for the special case is:
> > /*
> >  * Provide an identity mapping of gsi == irq except on truly
> >  * weird platforms that have non isa irqs in the first 16 gsis.
> >  */
> > return gsi >= NR_IRQS_LEGACY ? gsi : gsi_top + gsi;
> 
> That looks really, really wrong. What's wrong with assigning that irq
> irq number on those platforms?
> 
> The weird stuff is SFI and devicetree, if I understand your code
> correctly.
> 
> So if those platforms do not have actual legacy irqs, what's wrong
> with giving out the legacy numbers?

Though if it's a real issue, we can simply mark the ioapic on those
devices as DYNAMIC and avoid that whole magic.

Thanks,

	tglx