linux-kernel - Re: Multiple MSI

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-Id: <1215067484.17950.35.camel@localhost>
Date:	Thu, 03 Jul 2008 16:44:44 +1000
From:	Michael Ellerman <michaele@....ibm.com>
To:	benh@...nel.crashing.org
Cc:	Matthew Wilcox <matthew@....cx>, linux-pci@...r.kernel.org,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Miller <davem@...emloft.net>,
	Dan Williams <dan.j.williams@...el.com>,
	Martine.Silbermann@...com, linux-kernel@...r.kernel.org,
	Michael Ellerman <michaele@....ibm.com>
Subject: Re: Multiple MSI

On Thu, 2008-07-03 at 14:41 +1000, Benjamin Herrenschmidt wrote:
> On Wed, 2008-07-02 at 21:59 -0600, Matthew Wilcox wrote:
> > 
> > 
> > This is true and worth considering carefully.  Are IRQ numbers a scarce
> > resource on PowerPC?  They are considerably less scarce than interrupt
> > vectors are on x86-64.  How hard is it to make IRQ numbers an abundent
> > resource?  Is it simply a question of increasing NR_IRQS?
> 
> Yes, indeed, they aren't really scarce... actually less than the
> underlying HW vectors in most cases, so it isn't a big issue to add some
> kind of constraint to the allocator.

Not scarce, but increasing NR_IRQS makes some static arrays bigger,
which is not so nice.

> > By the way, would people be interested in changing the MSI-X API to get
> > rid of the msix_entry array?  If allocating consecutive IRQs isn't a
> > problem, then we could switch the MSI-X code to use consecutive IRQs.
> 
> It would make a lot of code simpler...

It's not a pretty API to be sure. I thought drivers needed the
flexibility of being able to specify non-contiguous ranges. In practice
it looks like only s2io is doing anything different.

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

email: michaele@...ibm.com
stime: ellerman@....ibm.com
notes: Michael Ellerman/Australia/IBM
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person

--
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/