Alexander Graf <ag...@suse.de> writes: > On 27.01.2014, at 11:28, Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com> > wrote: > >> Alexander Graf <ag...@suse.de> writes: >> >>> On 21.01.2014, at 10:42, Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com> >>> wrote: >>> >>>> Liu Ping Fan <kernelf...@gmail.com> writes: >>>> >>>>> To make sure that on host, the pages marked with _PAGE_NUMA result in a >>>>> fault >>>>> when guest access them, we should force the checking when guest uses >>>>> hypercall >>>>> to setup hpte. >>>>> >>>>> Signed-off-by: Liu Ping Fan <pingf...@linux.vnet.ibm.com> >>>> >>>> Reviewed-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com> >>>> >>>> When we mark pte with _PAGE_NUMA we already call >>>> mmu_notifier_invalidate_range_start and >>>> mmu_notifier_invalidate_range_end, which will mark existing guest hpte >>>> entry as HPTE_V_ABSENT. Now we need to do that when we are inserting new >>>> guest hpte entries. This patch does that. >>> >>> So what happens next? We insert a page into the HTAB without >>> HPTE_V_VALID set, so the guest will fail to use it. If the guest does >>> an H_READ on it it will suddenly turn to V_VALID though? >> >> As per the guest the entry is valid, so yes an hread should return a >> valid entry. But in real hpte we would mark it not valid. > > Ah, yes. > >> >>> >>> I might need a crash course in the use of HPTE_V_ABSENT. >> >> When guest tries to access the address, the host will handle the fault. >> >> kvmppc_hpte_hv_fault should give more info > > Thanks for the pointer. So we fault it in lazily. Is there any > particular reason we can't do that on h_enter already? After all this > just means an additional roundtrip because the guest is pretty likely > to use the page it just entered, no?
We could get wrong numa fault information if we didn't do h_enter from the right node from which we faulted. -aneesh _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
