On 18/07/2019 07:52, Juergen Gross wrote: > Today there is a global limit of pages mapped via /dev/xen/gntdev set > to 1 million pages per default.
The Xen default limit even for dom0 is 1024 pages * 16 entries per page, which is far lower than this limit. > There is no reason why that limit is > existing, as total number of foreign mappings is limited by the s/foreign/grant/ ? > hypervisor anyway and preferring kernel mappings over userspace ones > doesn't make sense. Its probably also worth stating that this a root-only device, which further brings in to question the user/kernel split. > > Additionally checking of that limit is fragile, as the number of pages > to map via one call is specified in a 32-bit unsigned variable which > isn't tested to stay within reasonable limits (the only test is the > value to be <= zero, which basically excludes only calls without any > mapping requested). So trying to map e.g. 0xffff0000 pages while > already nearly 1000000 pages are mapped will effectively lower the > global number of mapped pages such that a parallel call mapping a > reasonable amount of pages can succeed in spite of the global limit > being violated. > > So drop the global limit and introduce per call limit instead. Its probably worth talking about this new limit. What is it trying to protect? ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
