[I got some help from BenC and mjg59 on freenode's #ubuntu-kernel] It turns out that the kernel's IOCTL code just bails (returns an all-0 struct) if the MTRR size field is >=4G. There is no room in the size field of struct mtrr_gentry (defined in /usr/include/asm/mtrr.h).
See case MTRRIOC_GET_ENTRY in arch/x86/kernel/cpu/mtrr/if.c I think that the struct field should be widened. But that may be an ABI change. Otherwise, the IOCTL should return an error. Perhaps EOVERFLOW or ERANGE. This seems to be a general Linux problem and not specific to Ubuntu. -- MTRR ioctls don't work as documented https://bugs.launchpad.net/bugs/253204 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
