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 11:52:26 +0300 Message-ID: <560CF44A.60102@scylladb.com> References: <560BCD2F.5060505@cloudius-systems.com> <20150930150115-mutt-send-email-mst@redhat.com> <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> 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-f181.google.com (mail-wi0-f181.google.com [209.85.212.181]) by dpdk.org (Postfix) with ESMTP id C59B58E59 for ; Thu, 1 Oct 2015 10:52:28 +0200 (CEST) Received: by wicfx3 with SMTP id fx3so17964496wic.0 for ; Thu, 01 Oct 2015 01:52:28 -0700 (PDT) In-Reply-To: <20151001113828-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 11:44 AM, Michael S. Tsirkin wrote: > On Wed, Sep 30, 2015 at 11:40:16PM +0300, Michael S. Tsirkin wrote: >>> And for what, to prevent >>> root from touching memory via dma that they can access in a million other >>> ways? >> So one can be reasonably sure a kernel oops is not a result of a >> userspace bug. > Actually, I thought about this overnight, and it should be possible to > drive it securely from userspace, without hypervisor changes. Also without the performance that was the whole reason from doing it in userspace in the first place. 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. > See > > https://mid.gmane.org/20151001104505-mutt-send-email-mst@redhat.com > > >