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[Qemu-devel] Bottom halves VS timers
From: |
Pavel Dovgalyuk |
Subject: |
[Qemu-devel] Bottom halves VS timers |
Date: |
Tue, 22 Jan 2019 10:15:03 +0300 |
Hi!
I recently debugged record/replay for some platform which uses PIO access for
IDE.
Handlers for these operations are called through BHs.
Scheduling new BH does not create a signal for the vCPU to suspend the
execution and
process the main loop events (in record/replay we synchronize these two
threads).
Therefore vCPU may execute 10000000 instruction until BH processing and the
guest
software may get a timeout.
I thought about replacing BH to the timers with period=0. This solution has the
following
properties:
1. Avoid code duplication (BH and timers do virtually the same operations)
2. Timers affect the vCPU - adding new virtual timer suspends the
execution to process the
callback
3. Timers are deterministic in record/replay mode (virtual ones of
course). We have similar
deterministic concept for BHs, but selecting between virtual and realtime
should be more familiar
for other developers.
4. Timers require a little bit more code, but this could be solved with
better interfaces
What do you think about this?
Did I miss anything?
Pavel Dovgalyuk
- [Qemu-devel] Bottom halves VS timers,
Pavel Dovgalyuk <=