[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] vNUMA and automatic numa balancing
>>> On 08.10.13 at 19:14, Elena Ufimtseva <ufimtseva@xxxxxxxxx> wrote: > couple of questions about Xen page fault trap: > > a) In spurious_page_fault/__page_fault_type in traps.c there is a page > walk performed and page table entries are being compared with > required_flags > field. It includes _PAGE_PRESENT for all levels of page entries from l4 to > l1. > How this flag is set for l4 differ from one for l2 or l1? Or it is the > same interpretation that means that the following level of page table > entries should be checked as the > one that caused page fault? Not sure I understand what you're asking, as this is hardware dictated behavior: _PAGE_PRESENT means the next lower level of page table exists, unless (a) we're already at L1 or (b) _PAGE_PSE is set at L2 or L3. > b) In spurious_page_fault routine the page fault is not supposed to be > fixed, as I understand, but just to determine the type (real, smep.. ) > If the spurious page fault detects the real fault, then it might be > transparently fixed later or return to the guest handler as is. Is > this correct? Indeed spurious_page_fault() doesn't do anything but determination, telling its caller how to behave. But no, transparent fixing of guest mode faults happens only _before_ spurious_page_fault() gets called, not after (and hence not taking into account its result). Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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