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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