From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yongji Xie Subject: Re: [PATCH 5/5] vfio-pci: Allow to mmap MSI-X table if interrupt remapping is supported Date: Thu, 5 May 2016 19:42:38 +0800 Message-ID: <4be013bc-e81b-84c5-06d3-e1b3f46b3227@linux.vnet.ibm.com> References: <1461761010-5452-1-git-send-email-xyjxie@linux.vnet.ibm.com> <1461761010-5452-6-git-send-email-xyjxie@linux.vnet.ibm.com> <063D6719AE5E284EB5DD2968C1650D6D5F4B52B5@AcuExch.aculab.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D5F4B52B5-VkEWCZq2GCInGFn1LkZF6NBPR1lH4CV8@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: David Laight , "'Tian, Kevin'" , "kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" Cc: "alistair-Y4h6yKqj69EXC2x5gXVKYQ@public.gmane.org" , "nikunj-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org" , "zhong-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org" , "eric.auger-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org" , "aik-sLpHqDYs0B2HXe+LvDLADg@public.gmane.org" , "mpe-Gsx/Oe8HsFggBc27wqDAHg@public.gmane.org" , "ruscur-3Su/lFKaw5ejKv3TNrM5DQ@public.gmane.org" , "will.deacon-5wv7dgnIgG8@public.gmane.org" , "gwshan-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org" , "warrier-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org" , "paulus-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org" , "benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org" , "bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org" List-Id: iommu@lists.linux-foundation.org Hi David and Kevin, On 2016/5/5 17:54, David Laight wrote: > From: Tian, Kevin >> Sent: 05 May 2016 10:37 > ... >>> Acutually, we are not aimed at accessing MSI-X table from >>> guest. So I think it's safe to passthrough MSI-X table if we >>> can make sure guest kernel would not touch MSI-X table in >>> normal code path such as para-virtualized guest kernel on PPC64. >>> >> Then how do you prevent malicious guest kernel accessing it? > Or a malicious guest driver for an ethernet card setting up > the receive buffer ring to contain a single word entry that > contains the address associated with an MSI-X interrupt and > then using a loopback mode to cause a specific packet be > received that writes the required word through that address. > > Remember the PCIe cycle for an interrupt is a normal memory write > cycle. > > David > If we have enough permission to load a malicious driver or kernel, we can easily break the guest without exposed MSI-X table. I think it should be safe to expose MSI-X table if we can make sure that malicious guest driver/kernel can't use the MSI-X table to break other guest or host. The capability of IRQ remapping could provide this kind of protection. Thanks, Yongji