git: nvmm - Use a critical section around the vmrun again

[Aaron LI]

commit 665a79c84141f1c0d18b69b7cf1c016190578177
Author: Matthew Dillon <dillon at apollo.backplane.com>
Date:   Thu Jul 15 14:00:09 2021 -0700

    nvmm - Use a critical section around the vmrun again
    
    * In DragonFly, a thread in kernel mode will not be preemptively migrated
      to another CPU or preemptively switched to another normal kernel thread,
      but can be preemptively switched to an interrupt thread (which switches
      back to the kernel thread it preempted the instant it is done or blocks).
    
      However, we still need to use a critical section to prevent this nominal
      interrupt thread preemption to avoid exposing interrupt threads to
      guest DB and FP register state.  We operate under the assumption that
      the hard interrupt code won't mess with this state.

Summary of changes:
 sys/dev/virtual/nvmm/nvmm_os.h | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/665a79c84141f1c0d18b69b7cf1c016190578177


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