[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v02 1/7] arm: introduce remoteprocessor iommu module
Hi Ian On Wed, Jul 16, 2014 at 6:34 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote: > On Wed, 2014-07-16 at 16:29 +0100, Ian Campbell wrote: >> 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? > > Reading the next patch I'm concluding that the translation happens each > time you write to the MMU's base pointer. IOW every update requires you > to rewrite that pointer, is that right? > Not exactly. Continuing an explanation from prev mail - this just an entry point for translation. IPU and GPU work in a bit different way. IPU is quite straight forward Boot -> Allocate all memory -> Update register -> Xen performs translation GPU: Step one: Reset -> Allocate several pages of memory -> Update register -> Xen performas translation Step two: Allocate several new pagetables -> Flush caches -> call do_translate_pagetable hypercall Here I don't have any registers update. GPU kernel driver uses interprocess messaging mechanism to pass physical pointers of newly allocated pagetables directly to GPU device. So, I use hypercall which translate pagetable during device creation. Regards, Andrii > Ian. > -- Andrii Tseglytskyi | Embedded Dev GlobalLogic www.globallogic.com _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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