From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751936AbbJELll (ORCPT ); Mon, 5 Oct 2015 07:41:41 -0400 Received: from mail-wi0-f170.google.com ([209.85.212.170]:33683 "EHLO mail-wi0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751198AbbJELlk (ORCPT ); Mon, 5 Oct 2015 07:41:40 -0400 Subject: Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support To: Greg KH 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> <20151005105715.GA23459@kroah.com> 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 From: Vlad Zolotarov Message-ID: <561261EF.8010101@cloudius-systems.com> Date: Mon, 5 Oct 2015 14:41:35 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <20151005105715.GA23459@kroah.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/05/15 13:57, Greg KH wrote: > 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? I think they are "int" on all platforms and as far as I know u32 should be enough to contain int on any platform. > > And NEVER use the _t types in kernel code, Never meant it - it was for a user space interface. For a kernel it's u32 of course. > the namespaces is all wrong > and it is not applicable for us, sorry. > > thanks, > > greg k-h