[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [Xen-users] ARM: "xen_add_mach_to_phys_entry: cannot add ... already exists and panics"
On 04/07/14 15:12, Stefano Stabellini wrote: > On Fri, 4 Jul 2014, David Vrabel wrote: >> On 03/07/14 18:47, Stefano Stabellini wrote: >>> >>> At the moment I would like a way to disable grant mappings and go back >>> to grant copies on demand. Maybe we could have a feature flag to change >>> the behaviour of the network backend? >> >> You must fix the ARM code to handle this properly. >> >> blkback also uses grant maps and depending on the frontend blkback may >> grant map the same machine frame multiple time. We have see frontends >> that send such requests. > > Indeed, it must be fixed properly. The workaround of disabling grant > mappings would be just to buy us some time to come up with the fix. It's an expensive workaround though. >> I can't remember how the ARM code works. Where is the problematic m2p >> lookup? > > arch/arm/xen/p2m.c > > >> Perhaps this could be avoided for foreign frames? > > Unfortunately no. The whole point of p2m.c is to be able to translate > foreign frames for dma operations. This is a p2m lookup though, which is fine, yes? Where, specifically is a mfn_to_pfn() lookup needed for a foreign MFN. FWIW, On x86, mfn_to_pfn() on a foreign MFN will return an invalid value (unless the gntdev device made the mapping and the m2p_override is used). David _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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