plugin: only pause on EINTR

In the case of 1) an IO exit & callout to plugin, then 2) a pause
request by another thread, the vcpu thread will eagerly check for a
pause request and might cause another callout to the plugin for the
pause.  We haven't yet run KVM again for it to emulate the completion of
the IO.  It's probably less risky to call back into KVM again and let it
finish the emulation before we callout to the plugin to make other
potential state changes to the VM.  This change also reduces the
overhead of the non-pause case by not checking for a pause request on
each VM exit.

The tradeoff is that a pause request might take longer, but these are
(or should be) relatively rare so it's better to slow these down (and be
more conserative/sane about the state of the VM when pause is reported)
in favor of making the non-pause VM exits faster.

BUG=None
TEST=Local build and run of "build_test".

Change-Id: I38609eccd9a2196835f99de5ea84a586928fab30
Signed-off-by: Matt Delco <delco@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1863725
Reviewed-by: Zach Reizner <zachr@chromium.org>

0 files changed, 0 insertions, 0 deletions