On Tue, Apr 12, 2016 at 02:03:25PM +0100, Suzuki K Poulose wrote: > On 12/04/16 13:14, Christoffer Dall wrote: > >On Mon, Apr 11, 2016 at 03:33:45PM +0100, Suzuki K Poulose wrote: > >>On 08/04/16 16:05, Christoffer Dall wrote: > >>>On Mon, Apr 04, 2016 at 05:26:15PM +0100, Suzuki K Poulose wrote: > >> > > >>>>-#if PGDIR_SHIFT > KVM_PHYS_SHIFT > >>>>-#define PTRS_PER_S2_PGD_SHIFT 0 > >>>>-#else > >>>>-#define PTRS_PER_S2_PGD_SHIFT (KVM_PHYS_SHIFT - PGDIR_SHIFT) > >>>>-#endif > >>>>-#define PTRS_PER_S2_PGD (1 << PTRS_PER_S2_PGD_SHIFT) > >>>>+#define STAGE2_PGTABLE_LEVELS ARM64_HW_PGTABLE_LEVELS(KVM_PHYS_SHIFT - 4) > >>>> > >>>> /* > >>>>- * If we are concatenating first level stage-2 page tables, we would have less > >>>>- * than or equal to 16 pointers in the fake PGD, because that's what the > >>>>- * architecture allows. In this case, (4 - CONFIG_PGTABLE_LEVELS) > >>>>- * represents the first level for the host, and we add 1 to go to the next > >>>>- * level (which uses contatenation) for the stage-2 tables. > > > >just noticed: s/contatenation/concatenation/ > > Thanks for catching that. Will fix it. > > >>>which case this should be reworded to just state the assumptions and why > >>>this is a good assumption. > >>> > >>>(If my assumptions are wrong here, then there are also weird cases where > >>>the host does huge pages at the PMD level and we don't. Not sure I can > >>>see the full ramifications of that.) > >> > >>I am sorry, I didn't get your point about the PMD level. > >> > > > >Right, I expressed that terribly, and I may have gotten myself confused > >when writing that. > > > >My concern is this: if the number of levels between the host and stage-2 > >are different, and the host uses huge pmd mappings (either THP or huge > >tlb fs), then do we always do the right thing for stage-2 tables, even > >if we support the case with more levels in Stage-2 than on the host? > > Yes. We are safe with PMD (level 2). In the worst case we will have a 2level > page table at host and say 4 at stage2. In either case, we have a PMD level > (which in host is folded to PGD) and both will use section mapping at level 2 > for huge pmd. Also pmd_huge() doesn't care if the PMD is folded or not. So, > we are fine with that. I hope that answers your question. > It does, thanks for enumerating the cases for me. > > > >Thanks for trying to parse my crytptic and potentially nonsensical > >questions. > > No no, they make absolute sense. I had gone through these questions myself initially > when I wrote the series, so its good to share them :-). > > Btw, I have rebased my series to kvmarm and have addressed the comments. I will post > them after a round of testing. > Great, thanks! -Christoffer -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
