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Re: [Qemu-devel] add 'monitor' and 'mwait' instruction (update)
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] add 'monitor' and 'mwait' instruction (update) |
Date: |
Sun, 9 Jul 2006 12:30:23 +0100 |
User-agent: |
KMail/1.9.3 |
> > Problem is, at the moment I've no idea, how we could achieve this memory
> > monitoring in a safe and simple way in user space.
>
> I'm trying to read up on monitor and mwait. Apparently mwait puts the
> processor in low-power wait mode, waiting for a memory write in some
> select area defined by monitor; and as I am new to this I'm not sure if
> I have understood all sources from where such a memory write can come
> from while the processor is asleep. One source, I suppose, is from other
> processors in an SMP setup? Another source may be DMA? Does this mean
> that it is safe to emulate wmait as hlt if neiter SMP or DMA is used?
> (Qemu hardware doesn't support DMA, right?)
qemu hardware does support DMA, but I don't think this matters.
By my reading DMA writes don't need to wake mwait.
The exact wording is "store operation", which I'd expect to mean execution of
a store instruction (by a different CPU). So for UP systems mwait can be
implemented the same as HLT, except that it raises an exception if state
hasn't been initialized by monitor.
Paul
- [Qemu-devel] [PATCH] add 'monitor' and 'mwait' instruction, (continued)
- [Qemu-devel] [PATCH] add 'monitor' and 'mwait' instruction, Joachim Henke, 2006/07/07
- Re: [Qemu-devel] [PATCH] add 'monitor' and 'mwait' instruction, maestro, 2006/07/07
- [Qemu-devel] [PATCH] add 'monitor' and 'mwait' instruction (update), Joachim Henke, 2006/07/07
- Re: [Qemu-devel] [PATCH] add 'monitor' and 'mwait' instruction (update), R. Armiento, 2006/07/08
- Re: [Qemu-devel] add 'monitor' and 'mwait' instruction (update), Joachim Henke, 2006/07/08
- Re: [Qemu-devel] add 'monitor' and 'mwait' instruction (update), R. Armiento, 2006/07/08
- Re: [Qemu-devel] add 'monitor' and 'mwait' instruction (update), Joachim Henke, 2006/07/09
- Re: [Qemu-devel] add 'monitor' and 'mwait' instruction (update), R. Armiento, 2006/07/09
- Re: [Qemu-devel] add 'monitor' and 'mwait' instruction (update),
Paul Brook <=
- Re: [Qemu-devel] add 'monitor' and 'mwait' instruction (update), Jamie Lokier, 2006/07/09
- Re: [Qemu-devel] 'monitor' and 'mwait' instruction, Joachim Henke, 2006/07/09
- Re: [Qemu-devel] add 'monitor' and 'mwait' instruction (update), Jamie Lokier, 2006/07/09
- Re: [Qemu-devel] add 'monitor' and 'mwait' instruction (update), Jamie Lokier, 2006/07/09