From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from webmail.solarflare.com (webmail.solarflare.com [12.187.104.25]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (Client CN "WEBMAIL.SOLARFLARE.COM", Issuer "VeriSign Class 3 Secure Server CA - G3" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 0665A2C0338 for ; Tue, 8 Oct 2013 07:46:17 +1100 (EST) Message-ID: <1381178766.1536.26.camel@bwh-desktop.uk.level5networks.com> Subject: Re: [PATCH RFC 00/77] Re-design MSI/MSI-X interrupts enablement pattern From: Ben Hutchings To: Benjamin Herrenschmidt Date: Mon, 7 Oct 2013 21:46:06 +0100 In-Reply-To: <1381176656.645.171.camel@pasglop> References: <1380840585.3419.50.camel@bwh-desktop.uk.level5networks.com> <20131004082920.GA4536@dhcp-26-207.brq.redhat.com> <1380922156.3214.49.camel@bwh-desktop.uk.level5networks.com> <20131005142054.GA11270@dhcp-26-207.brq.redhat.com> <1381009586.645.141.camel@pasglop> <20131006060243.GB28142@dhcp-26-207.brq.redhat.com> <1381040386.645.143.camel@pasglop> <20131006071027.GA29143@dhcp-26-207.brq.redhat.com> <20131007180111.GC2481@htj.dyndns.org> <1381176656.645.171.camel@pasglop> Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Cc: linux-mips@linux-mips.org, "VMware, Inc." , linux-pci@vger.kernel.org, linux-nvme@lists.infradead.org, linux-ide@vger.kernel.org, linux-s390@vger.kernel.org, Andy King , linux-scsi@vger.kernel.org, linux-rdma@vger.kernel.org, x86@kernel.org, Alexander Gordeev , iss_storagedev@hp.com, linux-driver@qlogic.com, Martin Schwidefsky , Bjorn Helgaas , Dan Williams , Jon Mason , Ingo Molnar , Solarflare linux maintainers , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Ralf Baechle , e1000-devel@lists.sourceforge.net, Tejun Heo , linux390@de.ibm.com, linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, 2013-10-08 at 07:10 +1100, Benjamin Herrenschmidt wrote: > On Mon, 2013-10-07 at 14:01 -0400, Tejun Heo wrote: > > I don't think the same race condition would happen with the loop. The > > problem case is where multiple msi(x) allocation fails completely > > because the global limit went down before inquiry and allocation. In > > the loop based interface, it'd retry with the lower number. > > > > As long as the number of drivers which need this sort of adaptive > > allocation isn't too high and the common cases can be made simple, I > > don't think the "complex" part of interface is all that important. > > Maybe we can have reserve / cancel type interface or just keep the > > loop with more explicit function names (ie. try_enable or something > > like that). > > I'm thinking a better API overall might just have been to request > individual MSI-X one by one :-) > > We want to be able to request an MSI-X at runtime anyway ... if I want > to dynamically add a queue to my network interface, I want it to be able > to pop a new arbitrary MSI-X. Yes, this would be very useful. > And we don't want to lock drivers into contiguous MSI-X sets either. I don't think there's any such limitation now. The entries array passed to pci_enable_msix() specifies which MSI-X vectors the driver wants to enable. It's usually filled with 0..nvec-1 in order, but not always. And the IRQ numbers returned aren't usually contiguous either, on x86. Ben. > And for the cleanup ... well that's what the "pcim" functions are for, > we can just make MSI-X variants. -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.