> From: Jan Beulich [mailto:jbeul...@suse.com] > Sent: Tuesday, September 4, 2018 5:08 PM > > >>> 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. >
Then Paul please documents clearly that this bus address refers to the input side of IOMMU. :-) Thanks Kevin _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
