>>> On 04.09.18 at 10:49, <paul.durr...@citrix.com> wrote: >> -----Original Message----- >> From: Jan Beulich [mailto:jbeul...@suse.com] >> Sent: 04 September 2018 09:47 >> To: Kevin Tian <kevin.t...@intel.com> >> Cc: Suravee Suthikulpanit <suravee.suthikulpa...@amd.com>; Julien Grall >> <julien.gr...@arm.com>; Paul Durrant <paul.durr...@citrix.com>; Stefano >> Stabellini <sstabell...@kernel.org>; xen-devel <xen- >> de...@lists.xenproject.org> >> Subject: Re: [Xen-devel] [PATCH v6 01/14] iommu: introduce the concept of >> BFN... >> >> >>> On 04.09.18 at 10:37, <kevin.t...@intel.com> wrote: >> >> From: Jan Beulich [mailto:jbeul...@suse.com] >> >> Sent: Tuesday, September 4, 2018 4:33 PM >> >> > >> >> > bus address is commonly used along with physical/virtual address, to >> >> > represent different views between devices and CPU. From that angle >> >> > I think BFN is a clear term in this context. btw it is not necessary to >> >> > differentiate GBFN and MBFN since there is only one BFN view per >> >> > device. >> >> >> >> Sure, but you neglect the presence of one or more IOMMUs when >> >> you say "between devices and CPU". There addresses prior to and >> >> after IOMMU translation are distinct, and while the one before the >> >> translation matches the device view, the one after translation does >> >> not necessarily match the CPU view. Hence there are two "bus" >> >> frame numbers here - one representing the device view, and the >> >> other representing the IOMMU (output) view. >> >> >> > >> > I didn't get. the output address from IOMMU is the one sent to >> > memory controller, same as the one sent from CPU. >> >> That's on present x86 systems, but aiui not in the general case. The >> terminology to be used in Xen should fit the general case though. > > So your concern is cascaded IOMMUs?
Not primarily. My concern are systems with an I/O address space (behind the IOMMU) distinct from the CPU address space. Iirc at least Alpha is/was that way. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
