git: kernel - Intel user/kernel separation MMU bug fix part 4

Matthew Dillon dillon at
Fri Jan 5 10:23:27 PST 2018

commit 6a0fee0421666437f4456da13dbf682a919717cb
Author: Matthew Dillon <dillon at>
Date:   Fri Jan 5 09:52:13 2018 -0800

    kernel - Intel user/kernel separation MMU bug fix part 4
    * This completes 99% of the meltdown mitigation work, implementing
      a feature which isolates user and kernel page tables.  There
      are currently two remaining TODO's:
      (1) We still map all of kernel text (btext to etext) to avoid
          having to tabulate vector entry and exit points.  No
          kernel data or bss or any other kernel data is mapped,
          beyond trampoline and cpu hw requirements.
      (2) iretq + %gs fault bug needs to be re-tested.
    * Automate enablement of machdep.isolated_user_pmap added.
      The bug mitigation will be enabled for all Intel CPUs.
      This will increase system call and interrupt overhead by
      150-250nS.  System-call-heavy or interrupt-heavy workloads
      will be more severely effected (network, database, high speed
      storage, etc), up to 30%.  Nominal workloads such as compiles will
      lose around 5%.
    * Cleanup boot messages (zrj).
    * Rename sysctl from vm.isolated_user_pmap to
      machdep.isolated_user_pmap (zrj)

Summary of changes:
 sys/platform/pc64/x86_64/pmap.c | 52 +++++++++++++++++++++++++++++------------
 1 file changed, 37 insertions(+), 15 deletions(-)

DragonFly BSD source repository

More information about the Commits mailing list