From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH v1 2/2] dma-mapping-common: add DMA attribute - DMA_ATTR_IOMMU_BYPASS Date: Wed, 28 Oct 2015 17:23:39 -0700 (PDT) Message-ID: <20151028.172339.458418017721569530.davem@davemloft.net> References: <1446039110.3405.212.camel@infradead.org> <20151028.070705.1277125569024626755.davem@davemloft.net> <1446040632.3405.222.camel@infradead.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1446040632.3405.222.camel@infradead.org> Sender: linux-doc-owner@vger.kernel.org List-Archive: List-Post: To: dwmw2@infradead.org Cc: shamir.rabinovitch@oracle.com, arnd@arndb.de, corbet@lwn.net, linux-doc@vger.kernel.org, linux-arch@vger.kernel.org, luto@kernel.org, jroedel@suse.de, borntraeger@de.ibm.com, cornelia.huck@de.ibm.com, sebott@linux.vnet.ibm.com, pbonzini@redhat.com, hch@lst.de, benh@kernel.crashing.org, kvm@vger.kernel.org, schwidefsky@de.ibm.com, linux-s390@vger.kernel.org List-ID: From: David Woodhouse Date: Wed, 28 Oct 2015 22:57:12 +0900 > On Wed, 2015-10-28 at 07:07 -0700, David Miller wrote: >> In the sparc64 case, the 64-bit DMA address space is divided into >> IOMMU translated and non-IOMMU translated. >> >> You just set the high bits differently depending upon what you want. > > Wait, does that mean a (rogue) device could *always* get full access to > physical memory just by setting the high bits appropriately? That > mapping is *always* available? The IOMMU supports several modes, one of which disallows passthrough and this is what you would use in a virtual guest.