CVSROOT: /cvs
Module name: src
Changes by: bl...@cvs.openbsd.org 2021/06/04 05:02:50
Modified files:
sys/arch/amd64/amd64: Tag: OPENBSD_6_8 locore.S
Log message:
Don't clear the cpu's bit in the old pmap's pm_cpus until we're off
the old one and set it in the new pmap's pm_cpus before loading
%cr3 with the new value. In particular, do neither if %cr3 isn't
changing.
This eliminates a window where, when switching between threads in
a single a process, the pmap wouldn't have this cpu's bit set even
though we didn't change %cr3. With more of uvm unlocked, it was
possible for another cpu to update the page tables but not see a
need to send an IPI to this cpu, leading to crashes when TLB entries
that should have been invalidated were used.
malloc_duel testing by abluhm@
ok abluhm@ kettenis@ mlarkin@
from guenther@
this is errata/6.8/023_cpuswitch.patch.sig
