Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33
From: Gregory Haskins
Date: Tue Dec 22 2009 - 14:15:53 EST
On 12/22/09 1:53 PM, Avi Kivity wrote:
> I asked why the irqfd/ioeventfd mechanisms are insufficient, and you did not reply.
>
BTW: the ioeventfd issue just fell through the cracks, so sorry about
that. Note that I have no specific issue with irqfd ever since the
lockless IRQ injection code was added.
ioeventfd turned out to be suboptimal for me in the fast path for two
reasons:
1) the underlying eventfd is called in atomic context. I had posted
patches to Davide to address that limitation, but I believe he rejected
them on the grounds that they are only relevant to KVM.
2) it cannot retain the data field passed in the PIO. I wanted to have
one vector that could tell me what value was written, and this cannot be
expressed in ioeventfd.
Based on this, it was a better decision to add a ioevent interface to
xinterface. It neatly solves both problems.
Kind Regards,
-Greg
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