[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Every page fault caused pagetable walk when using xenoprofile
At 08:15 +0100 on 17 Jul (1247818543), ZelluX wrote: > ==== BLAH BLAH BLAH ==== Hey, the registers might have been useful! :) > (XEN) [<ffff828c80152cb6>] __copy_from_user_ll+0x26/0x40 > (XEN) [<ffff828c801a5cba>] xenoprof_backtrace+0xfa/0x440 > (XEN) [<ffff828c8011c105>] xenoprof_log_event+0xe5/0x1b0 > (XEN) [<ffff828c801a584e>] ppro_check_ctrs+0x9e/0x120 > (XEN) [<ffff828c801a47a9>] nmi_callback+0x29/0x80 > (XEN) [<ffff828c8014e518>] do_nmi+0x38/0x100 > (XEN) [<ffff828c801a6877>] handle_ist_exception+0x52/0x5b > (XEN) > (XEN) d0:v10: reserved bit in page table (ec=0009) > (XEN) Pagetable walk from 0000000000402540: > (XEN) L4[0x000] = 000000056265c067 5555555555555555 > (XEN) L3[0x000] = 000000056212b067 5555555555555555 > (XEN) L2[0x002] = 000000056215d067 5555555555555555 > (XEN) L1[0x002] = ffffffffffffffff ffffffffffffffff That's the marker that the shadow pagetables use to register that they know the equivalent guest L1 entry is not present. It allows a lock-free fast path in the shadow pagetable code to be keyed off the pagefault error code. In this case, it looks like xen is trying to copy data from a buffer in dom0 that's not mapped, which causes a reserved-bit page fault, and because the fault is taken in Xen context it prints a warning. Two things: - does xenoprofile normally get a lot of hypercalls returning EFAULT? Are you passing buffers to Xen that aren't mlock()ed? - does commenting out the call to reserved_bit_page_fault() in do_page_fault() make everything Just Work? I think it should, but maybe Keir will disagree. Cheers Tim. -- Tim Deegan <Tim.Deegan@xxxxxxxxxx> Principal Software Engineer, Citrix Systems (R&D) Ltd. [Company #02300071, SL9 0DZ, UK.] _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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