On 3 June 2017 23:26:00 BST, Stuart Longland <stuartl@xxxxxxxxxxxxxxxxxx> wrote: >Hi Maciej, > >On 03/06/17 22:43, Maciej W. Rozycki wrote: >> On Sat, 3 Jun 2017, Stuart Longland wrote: >>> Now, on a single-processor MIPS64r2 VM, this same root filesystem >works. >>> It won't work though for a 8-core I6400 system. If I try to run a >SMP >>> MIPS64r2 VM, I get "unable to proceed without a CM", so clearly >there is >>> a feature in the I6400 that doesn't exist in the MIPS64r2. >> >> Your userland likely requires the legacy NaN encoding (as specified >by >> the IEEE 754-1985 floating point standard) whereas I6400 hardware >only >> supports the 2008 NaN encoding (as specified by the IEEE 754-2008 >floating >> point standard), as per the R6 architecture requirement. These >encodings >> are incompatible with each other and all binaries are annotated in >their >> ELF header as to which is required; use `readelf -h' and check >`Flags:' >> for the presence of `nan2008' among the features reported. > >Ahh, quite possible. I just compiled for MIPS III, not sure if that >supports this alternate NaN encoding. Also, i6400 is mips64r6, which is not fully binary compatible with r5 and older. you could build an r6 userland (which i think implies nan2008), or else double check you've enabled r2 emulation on r6 in your kernel configuration (which will be slower but should still work). >The ultimate target for this is >Loongson 2F which probably uses the old encoding. indeed. i think nan2008 is optional in r5, required in r6. -- James Hogan
