From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Having troubles binding an SR-IOV VF to uio_pci_generic on Amazon instance Date: Thu, 1 Oct 2015 12:22:46 +0300 Message-ID: <560CFB66.5050904@scylladb.com> References: <560BD284.7040505@cloudius-systems.com> <20150930151632-mutt-send-email-mst@redhat.com> <560BDE24.8000308@scylladb.com> <20150930165359-mutt-send-email-mst@redhat.com> <560BF782.4070308@scylladb.com> <20150930175848-mutt-send-email-mst@redhat.com> <560C0171.7080507@scylladb.com> <20150930204016.GA29975@redhat.com> <20151001113828-mutt-send-email-mst@redhat.com> <560CF44A.60102@scylladb.com> <20151001120027-mutt-send-email-mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: "dev@dpdk.org" To: "Michael S. Tsirkin" Return-path: Received: from mail-wi0-f172.google.com (mail-wi0-f172.google.com [209.85.212.172]) by dpdk.org (Postfix) with ESMTP id 1D0285A54 for ; Thu, 1 Oct 2015 11:22:49 +0200 (CEST) Received: by wicfx3 with SMTP id fx3so23434042wic.1 for ; Thu, 01 Oct 2015 02:22:49 -0700 (PDT) In-Reply-To: <20151001120027-mutt-send-email-mst@redhat.com> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 10/01/2015 12:15 PM, Michael S. Tsirkin wrote: > On Thu, Oct 01, 2015 at 11:52:26AM +0300, Avi Kivity wrote: >> I still don't understand your objection to the patch: >> >> >> MSI messages are memory writes so any generic device capable >> of MSI is capable of corrupting kernel memory. >> This means that a bug in userspace will lead to kernel memory corruption >> and crashes. This is something distributions can't support. >> >> >> If a distribution feels it can't support this configuration, it can disable the >> uio_pci_generic driver, or refuse to support tainted kernels. If it feels it >> can (and many distributions are starting to support dpdk), then you're just >> denying it the ability to serve its users. > I don't, and can't deny users anything. I merely think upstream should > avoid putting this driver in-tree. By doing this, driver writers will > be pushed to develop solutions that can't crash kernel. > > I pointed out one way to build it, there are sure to be more. And I pointed out that your solution is unworkable. It's easy to claim that a solution is around the corner, only no one was looking for it, but the reality is that kernel bypass has been a solution for years for high performance users, that it cannot be made safe without an iommu, and that iommus are not available everywhere; and even when they are some users prefer to avoid the performance penalty. > As far as I could see, without this kind of motivation, people do not > even want to try. You are mistaken. The problem is a lot harder than you think. People didn't go and write userspace drivers because they were lazy. They wrote them because there was no other way.