On 11/05/2014 11:09, Ralf Baechle wrote: > On Mon, Nov 03, 2014 at 05:23:29PM -0800, David Daney wrote: > >> I haven't checked, but there may be workarounds required in the TLB >> management code that are not in place for the huge page case. When the huge >> TLB code was developed, we didn't do any testing on R10K. Somebody should >> dump the exception handlers and carefully look at the rest of the huge TLB >> management code, and check to see that any required workarounds are in >> place. > > Joshua, if you happen to have R10000 errata sheets around, maybe you could > check if there's anything suspicious? Off the top of my head I don't recall > any R10000 TLB erratas but the R10000 had plenty of erratas due to it's - by > the standards of the time - high complexity. > > Ralf All I have are errata sheets for Rev 2.3, 2.4, and 2.5 of the R10K. Nothing specific on the R12K, and nil for the R14K/R16K. That said, poking through other areas of the R10K/R12K User Manual, there are paragraphs titled "Errata" and regarding the PageMask register or TLB, they state this: Page 41 The calculated address is translated from a 44-bit virtual address into a 40-bit physical address using a translation-lookaside buffer. The TLB contains 64 entries, each of which can translate two pages. Each entry can select a page size ranging from 4 Kbytes to 16 Mbytes, inclusive, in __powers__ of 4, as shown in Figure 1-6. Page 316: Translated virtual addresses retrieve data in blocks, which are called pages. In the R10000 processor, the size of each page may be selected from a range that runs from 4 Kbytes to 16 Mbytes inclusive, __in_powers_of_4__ (that is, 4 Kbytes, 16 Kbytes, 64 Kbytes, etc.). So my guess is unless hugepages can happen in powers of 4, they're not compatible w/ the R10K-series (and likely not the R5K/RM7K, either, since they all have the same 24:13 bits in the PageMask register). It seems the logical choice would be to remove 'select CPU_SUPPORTS_HUGEPAGES' from CPU_R5000, CPU_NEVADA, CPU_R10000, and CPU_RM7000 in arch/mips/Kconfig. -- Joshua Kinard Gentoo/MIPS kumba@xxxxxxxxxx 4096R/D25D95E3 2011-03-28 "The past tempts us, the present confuses us, the future frightens us. And our lives slip away, moment by moment, lost in that vast, terrible in-between." --Emperor Turhan, Centauri Republic
