From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH 05/16] iommu/amd: Split device table initialization into irq and dma part Date: Fri, 28 Sep 2012 16:25:55 +0200 Message-ID: <20120928142555.GC4009@amd.com> References: <1348835046-3262-1-git-send-email-joerg.roedel@amd.com> <1348835046-3262-6-git-send-email-joerg.roedel@amd.com> <20120928141752.GD7483@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20120928141752.GD7483-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@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: Konrad Rzeszutek Wilk Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: iommu@lists.linux-foundation.org On Fri, Sep 28, 2012 at 10:17:53AM -0400, Konrad Rzeszutek Wilk wrote: > On Fri, Sep 28, 2012 at 02:23:55PM +0200, Joerg Roedel wrote: > > When the IOMMU is enabled very early (as with irq-remapping) > > some devices are still in BIOS hand. When dma is blocked > > early this can cause lots of IO_PAGE_FAULTs. So delay the > > DMA initialization and do it right before the dma_ops are > > initialized. > > To be secure, block all interrupts by default when irq-remapping is > > What are you trying to be secure against? Against attacks of faked MSI msgs that could DoS the system. MSI messages are only specific DMA transactions in the end and a guest with a device assigned has control over its DMA engine and can thus send arbitrary interrupt requests to the host. There is a whole paper about such attacks. I can't find right now, but I send you a link when I find it. Joerg -- AMD Operating System Research Center Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach General Managers: Alberto Bozzo Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632