Hi Maciej, On Mon, Jul 11, 2016 at 03:56:09PM +0100, Maciej W. Rozycki wrote: > Hi James, > > > This will help some MIPS KVM code handling 32-bit guest addresses to > > work on 64-bit host kernels, but will also affect KSEGX in > > dec_kn01_be_backend() on a 64-bit DECstation kernel, and the SiByte DMA > > page ops KSEGX check in clear_page() and copy_page() on 64-bit SB1 > > kernels, neither of which appear to be designed with 64-bit segments in > > mind anyway. > > Thanks for the heads-up! > > This is not an issue however with `dec_kn01_be_backend', because the KN01 > baseboard used with the DECstation 2100 and 3100 computers has an R2000 > processor mounted in a permanent manner (no CPU daugthercard as with some > later baseboards) and will therefore never run a 64-bit kernel. In fact I > think kn01-berr.c would best only be built in 32-bit configurations. I Okay thanks, good to know. > never got to making such a clean-up though; I may look into it sometime as > I have some 2100/3100 stuff outstanding. > > As to the SiByte platform I have no clue offhand; there's surely some > stuff there across the port asking for a clean-up. I reckon using the > data mover for page ops is a kernel configuration option and I may have > never enabled it myself. Indeed, one that defaults to no and isn't enabled in any defconfigs. I think I'll update this patch to make that configuration depend on 32BIT, just in case any physical addresses of RAM have bits 31:29 = 0b100, which previously would have failed the test and fallen back to a CPU copy, but with this change would have carried on and mistranslated the pointer to a physical address on the assumption its in KSeg0. Cheers James
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