Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758899AbYGKV7y (ORCPT ); Fri, 11 Jul 2008 17:59:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754770AbYGKV7p (ORCPT ); Fri, 11 Jul 2008 17:59:45 -0400 Received: from mga02.intel.com ([134.134.136.20]:29220 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751514AbYGKV7o (ORCPT ); Fri, 11 Jul 2008 17:59:44 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.30,347,1212390000"; d="scan'208";a="309366550" Date: Fri, 11 Jul 2008 14:59:43 -0700 From: Suresh Siddha To: "Eric W. Biederman" Cc: Matthew Wilcox , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "grundler@parisc-linux.org" , "mingo@elte.hu" , "tglx@linutronix.de" , "jgarzik@pobox.com" , "linux-ide@vger.kernel.org" , "Siddha, Suresh B" , "benh@kernel.crashing.org" , "jbarnes@virtuousgeek.org" , "rdunlap@xenotime.net" , "mtk.manpages@gmail.com" Subject: Re: Multiple MSI, take 3 Message-ID: <20080711215943.GW1678@linux-os.sc.intel.com> References: <20080711005719.GO14894@parisc-linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1696 Lines: 42 On Fri, Jul 11, 2008 at 03:06:33AM -0700, Eric W. Biederman wrote: > Matthew Wilcox writes: > > > I'd like to thank Michael Ellerman for his feedback. This is a much > > better patchset than it used to be. > > There is a reason we don't have an API to support this. Linux can not > reasonably support this, especially not on current X86. The designers > of the of the AHCI were idiots and should have used MSI-X. > > Attempting to support multiple irqs in an MSI capability breaks > every interesting use of an irq. > > mask/unmask is will likely break because the mask bit is optional > and when it is not present we disable the msi capability. > > We can not set the affinity individually so we can not allow > different queues to be processed on different cores. > > So in general it seems something that we have to jump through a million > hurdles and the result is someones twisted parody of a multiple working > irqs, that even Intel's IOMMU can't cure. With interrupt-remapping, we can program the individual interrupt remapping table entries to point to different cpu's etc. All we have to take care is, do the IRTE allocation in a consecutive block and program the starting index to the MSI registers. Just curious Eric, why do you think that won't work? thanks, suresh > So unless the performance of the AHCI is better by a huge amount I don't > see the point, and even then I am extremely sceptical. > > Eric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/