From mboxrd@z Thu Jan 1 00:00:00 1970 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) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:cc:from:message-id:date :user-agent:mime-version:in-reply-to:content-type :content-transfer-encoding; bh=mEMgEhD+5MHmUCQAPrN9v8/XQDCWuwFSzbn7tnC1mGw=; b=I9OMqW7WSlTg/4Vt/YPCYDTjs85vRiHrYXfsyiE1z8gNSXiXHY2uGDVRgA4btQWZy9 n69/jKz45eRDSwnehqqdlBm/lXW+ge7DLtVTLTL1giKZRmZm1lADOHssTTq3fyOcrzdM dcPMVtE4aJqsDeTHMxx02X4FkJTQN8sC5e5waVoDNbunswCmFxMdm8r+C2qr4ti3T+hL 2Z50ZJGYA9WutfiM4E6Gjblcy4134Ht3LPN5WM+57Z1ibD7q8icfdd2QjC2gZGFtPjJb Vea+X2OQEPG+KoIQAjmGzpKugZzdG1wnCWLgWDO5NqnFPJ5DwfN1uEl2FewCqufJNCYG u3xQ== X-Gm-Message-State: ALoCoQmt6LHqXhq/4gOoQCLJTCiJPuZ7X5ceM02SSSLa1vMua0OUIu63i/xbp/xIALAwJtbmdF1h X-Received: by 10.194.121.40 with SMTP id lh8mr10348808wjb.115.1443691368909; Thu, 01 Oct 2015 02:22:48 -0700 (PDT) Received: from avi.cloudius ([37.142.229.250]) by smtp.googlemail.com with ESMTPSA id fz1sm2179731wic.8.2015.10.01.02.22.47 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Oct 2015 02:22:47 -0700 (PDT) To: "Michael S. Tsirkin" 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> From: Avi Kivity Message-ID: <560CFB66.5050904@scylladb.com> Date: Thu, 1 Oct 2015 12:22:46 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20151001120027-mutt-send-email-mst@redhat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] Having troubles binding an SR-IOV VF to uio_pci_generic on Amazon instance X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 01 Oct 2015 09:22:49 -0000 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.