linux-kernel - Re: [PATCH] virtio-balloon spec: provide a version of the "silent deflate" feature that works

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Date:	Mon, 10 Sep 2012 07:51:42 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	"Michael S. Tsirkin" <mst@...hat.com>, fes@...gle.com,
	aarcange@...hat.com, riel@...hat.com, kvm@...r.kernel.org,
	yvugenfi@...hat.com, linux-kernel@...r.kernel.org,
	mikew@...gle.com, yinghan@...gle.com,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] virtio-balloon spec: provide a version of the "silent
 deflate" feature that works

Il 10/09/2012 03:43, Rusty Russell ha scritto:
>> Now that vfio is upstream and work on qemu integration
>> is being worked on, we might finally see people using this bit
>> to allow memory overcommit with device assignment.
> That was left-field.... so you're saying some guest might pull a page
> from the balloon and DMA to it, and the vfio device needs to know in
> advance that it's going to do it?

Not the vfio device, but the page needs to be pinned with mlock so the
effect is the same.

> But what will we do if the guest doesn't ack the bit?

Just pin the whole memory.

Paolo

> ie. I don't think it can really be optional.

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