[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v02 1/7] arm: introduce remoteprocessor iommu module
On Thu, 2014-06-26 at 14:07 +0300, Andrii Tseglytskyi wrote: > This is a fisrst patch from patch series which was > developed to handle remote (external) processors > memory management units. Remote processors are > typically used for graphic rendering (GPUs) and > high quality video decoding (IPUs). They are typically > installed on such multimedia SoCs as OMAP4 / OMAP5. > > As soon as remoteprocessor MMU typically works with > pagetables filled by physical addresses, which are > allocated by domU kernel, it is almost impossible to > use them under Xen, intermediate physical addresses > allocated by kernel, need to be translated to machine > addresses. > > This patch introduces a simple framework to perform > pfn -> mfn translation for external MMUs. > It introduces basic data structures and algorithms > needed for translation. > > Typically, when MMU is configured, some it registers > are updated by new values. Introduced frameworks > uses traps as starting point of remoteproc MMUs > pagetables translation. Just to clarify the model: This is intended as a framework to enable Xen to provide an SMMU to the guest. Is the intention that this SMMU be an idealised PV thing or is it intending to emulate a real SMMU (and therefore the guests existing drivers)? I think this is the second one. And the intention here is to let the guest manipulate the page tables directly and shadow them from IPA->MA as opposed to e.g. exposing the guest's complete IPA->MA mapping to the remoteproc. I suppose either way my main concern is going to be the potential for proliferation of backends (and perhaps frontends) for all sorts of different H/W MMUs. I suppose that is unavoidable though. WRT the shadowing, I don't see the bit which causes the guest pages which it is using as PT page for the remoteproc to get marked R/O to force a trap. Perhaps that comes later. Do these remoteproc page tables get frequently updated at run time or are they mostly just build once and forget? Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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