From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751258AbbJELFk (ORCPT ); Mon, 5 Oct 2015 07:05:40 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:44675 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750824AbbJELFj (ORCPT ); Mon, 5 Oct 2015 07:05:39 -0400 Date: Mon, 5 Oct 2015 11:57:15 +0100 From: Greg KH To: Vlad Zolotarov Cc: linux-kernel@vger.kernel.org, mst@redhat.com, hjk@hansjkoch.de, corbet@lwn.net, bruce.richardson@intel.com, avi@cloudius-systems.com, gleb@cloudius-systems.com, stephen@networkplumber.org, alexander.duyck@gmail.com Subject: Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Message-ID: <20151005105715.GA23459@kroah.com> References: <1443991398-23761-1-git-send-email-vladz@cloudius-systems.com> <1443991398-23761-3-git-send-email-vladz@cloudius-systems.com> <20151005031159.GB27303@kroah.com> <561229B3.7000109@cloudius-systems.com> <20151005075628.GA1747@kroah.com> <56125587.40104@cloudius-systems.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56125587.40104@cloudius-systems.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 05, 2015 at 01:48:39PM +0300, Vlad Zolotarov wrote: > > > On 10/05/15 10:56, Greg KH wrote: > >On Mon, Oct 05, 2015 at 10:41:39AM +0300, Vlad Zolotarov wrote: > >>>>+struct msix_info { > >>>>+ int num_irqs; > >>>>+ struct msix_entry *table; > >>>>+ struct uio_msix_irq_ctx { > >>>>+ struct eventfd_ctx *trigger; /* MSI-x vector to eventfd */ > >>>Why are you using eventfd for msi vectors? What's the reason for > >>>needing this? > >>A small correction - for MSI-X vectors. There may be only one MSI vector per > >>PCI function and if it's used it would use the same interface as a legacy > >>INT#x interrupt uses at the moment. > >>So, for MSI-X case the reason is that there may be (in most cases there will > >>be) more than one interrupt vector. Thus, as I've explained in a PATCH1 > >>thread we need a way to indicated each of them separately. eventfd seems > >>like a good way of doing so. If u have better ideas, pls., share. > >You need to document what you are doing here, I don't see any > >explaination for using eventfd at all. > > > >And no, I don't know of any other solution as I don't know what you are > >trying to do here (hint, the changelog didn't document it...) > > > >>>You haven't documented how this api works at all, you are going to have > >>>to a lot more work to justify this, as this greatly increases the > >>>complexity of the user/kernel api in unknown ways. > >>I actually do documented it a bit. Pls., check PATCH3 out. > >That provided no information at all about how to use the api. > > > >If it did, you would see that your api is broken for 32/64bit kernels > >and will fall over into nasty pieces the first time you try to use it > >there, which means it hasn't been tested at all :( > > It has been tested of course ;) > I tested it only in 64 bit environment however where both kernel and user > space applications were compiled on the same machine with the same compiler > and it could be that "int" had the same number of bytes both in kernel and > in user space application. Therefore it worked perfectly - I patched DPDK to > use the new uio_pci_generic MSI-X API to test this and I have verified that > all 3 interrupt modes work: MSI-X with SR-IOV VF device in Amazon EC2 guest > and INT#x and MSI with a PF device on bare metal server. > > However I agree using uint32_t for "vec" and "fd" would be much more > correct. I don't think file descriptors are __u32 on a 64bit arch, are they? And NEVER use the _t types in kernel code, the namespaces is all wrong and it is not applicable for us, sorry. thanks, greg k-h