linux-kernel - Re: [Patch V4 12/42] x86, ioapic: kill static variable nr_irqs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <53999FA2.4000600@linux.intel.com>
Date:	Thu, 12 Jun 2014 20:40:02 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Grant Likely <grant.likely@...aro.org>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Yinghai Lu <yinghai@...nel.org>, x86@...nel.org,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tony Luck <tony.luck@...el.com>,
	Joerg Roedel <joro@...tes.org>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [Patch V4 12/42] x86, ioapic: kill static variable nr_irqs_gsi

Hi Thomas,
	With all patches applied, we have following code and comments
for this case:
        switch (type) {
        case IOAPIC_DOMAIN_LEGACY:
                /*
                 * Dynamically allocate IRQ number for non-ISA IRQs in
the first 16
                 * GSIs on some weird platforms.
                 */
                if (gsi < nr_legacy_irqs())
                        irq = irq_create_mapping(domain, pin);
                else if (irq_create_strict_mappings(domain, gsi, pin, 1)
== 0)
                        irq = gsi;
                break;


On 2014/6/12 18:58, Thomas Gleixner wrote:
> On Tue, 10 Jun 2014, Jiang Liu wrote:
> 
>> Hi Thomas,
>> 	This piece of code is inherited from current IOAPIC driver
>> and I think it's a workaround for some weird platforms.
>> 	For normal platforms with both 8259A and IOAPIC controllers,
>> legacy ISA IRQs should be connected to both 8259A and IOAPIC pins
>> (ignore timer and cascade IRQs for simplicity). According to comments
>>  in current kernel, there are some platforms on which:
>> 1) some ISA IRQs are only connected to 8259A controllers.
>> 2) the corresponding IOAPIC pins are connected to some non-ISA IRQs.
>> 	For such platforms, IRQ0-15 are used for ISA IRQs and another
>> 16 IRQs just above gsi_top are reserved for IOAPIC pins 0-15 which
>> are connected to non-ISA IRQs.
>> 	I have no real experience with such a platform, but just
>> guessing possible cases according to kernel comments and "Multiple
>> Processor Specification". Please look at these two pictures for quick
>> reference.
>> http://www.manualslib.com/manual/77733/Intel-Multiprocessor.html?page=31#manual
>> http://www.manualslib.com/manual/77733/Intel-Multiprocessor.html?page=63#manual
> 
> Duh. I completely forgot about the 82489 mess.
> 
> We probably want a comment somewhere why we have this gsi + legacy
> thing.
> 
> Thanks,
> 
> 	tglx
> 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/