From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: [PATCH RFC 00/77] Re-design MSI/MSI-X interrupts enablement pattern Date: Mon, 7 Oct 2013 21:46:06 +0100 Message-ID: <1381178766.1536.26.camel@bwh-desktop.uk.level5networks.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Tejun Heo , Alexander Gordeev , , Bjorn Helgaas , "Ralf Baechle" , Michael Ellerman , Martin Schwidefsky , Ingo Molnar , Dan Williams , Andy King , "Jon Mason" , Matt Porter , , , , , , , , , , , , , , "Solarflare linux maintainers" Return-path: In-Reply-To: <1381176656.645.171.camel@pasglop> Sender: linux-pci-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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.