Re: [PATCH 1/4] virtio-balloon: allow hypervisor refuse locking some pages

[Avi Kivity <avi@redhat.com>]

On 03/19/2010 10:46 PM, Dmitry Torokhov wrote:
> Some hypervisors may refuse our request to lock pages in certain
> circumstances. For example, VMware may decide that the target balloon
> size decreased since it was last communicated to the guest and thus
> current page should not be locked.
>
>
>   static struct virtio_driver virtio_balloon_driver = {
> diff --git a/include/linux/virtio_balloon.h b/include/linux/virtio_balloon.h
> index a50ecd1..4baad1c 100644
> --- a/include/linux/virtio_balloon.h
> +++ b/include/linux/virtio_balloon.h
> @@ -6,12 +6,16 @@
>   #include<linux/virtio_config.h>
>
>   /* The feature bitmap for virtio balloon */
> -#define VIRTIO_BALLOON_F_MUST_TELL_HOST	0 /* Tell before reclaiming pages */
> -#define VIRTIO_BALLOON_F_STATS_VQ	1 /* Memory Stats virtqueue */
> +#define VIRTIO_BALLOON_F_MUST_TELL_HOST		0 /* Tell before reclaiming pages */
> +#define VIRTIO_BALLOON_F_STATS_VQ		1 /* Memory Stats virtqueue */
> +#define VIRTIO_BALLOON_F_HOST_MAY_REFUSE	2 /* Host may refuse some pages */
>
>   /* Size of a PFN in the balloon interface. */
>   #define VIRTIO_BALLOON_PFN_SHIFT 12
>
> +#define VIRTIO_BALLOON_PFN_OK		0
> +#define VIRTIO_BALLOON_PFN_FAIL		1
> +
>   struct virtio_balloon_config
>   {
>   	/* Number of pages host wants Guest to give up. */
>    

Please update the virtio pci spec (can't find the URL - Rusty?) to 
reflect the protocol change.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.