Re: [PATCH 08/11] Add "wait for page" hypercall.

From: Avi Kivity
Date: Mon Nov 02 2009 - 10:19:30 EST

On 11/02/2009 05:13 PM, Gleb Natapov wrote:
On Mon, Nov 02, 2009 at 03:05:11PM +0200, Avi Kivity wrote:
On 11/01/2009 01:56 PM, Gleb Natapov wrote:
We want to be able to inject async pagefault into guest event if a guest
is not executing userspace code. But in this case guest may receive
async page fault in non-sleepable context. In this case it will be
able to make "wait for page" hypercall vcpu will be put to sleep until
page is swapped in and guest can continue without reschedule.
What's wrong with just 'hlt' and checking in the guest?

Halting here will leave vcpu with interrupt disabled and this will prevent
"wake up" signal delivery.

Page faults can be delivered with interrupts disabled.

Enabling interrupts is also not an options
since we can't be sure that vcpu can process interrupt at this point.

That's too bad, allowing interrupts in this context can help maintain responsiveness.

error compiling committee.c: too many arguments to function

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