On 18-06-11 11:19:00, nilal@xxxxxxxxxx wrote:
> From: Nitesh Narayan Lal <nilal@xxxxxxxxxx>
>
> This patch creates a new vq (hinting_vq) to be used for page hinting
> and adds support in the existing virtio balloon infrastructure so
> that the hyper list carrying pages which are supposed to be freed
> could be sent to the host (QEMU) for processing by using hinting_vq.
>
> Signed-off-by: Nitesh Narayan Lal <nilal@xxxxxxxxxx>
> ---
> drivers/virtio/virtio_balloon.c | 99 ++++++++++++++++++++++++++++++++++++-
> include/linux/page_hinting.h | 16 ++++++
> include/uapi/linux/virtio_balloon.h | 1 +
> virt/kvm/page_hinting.c | 36 ++++++--------
> 4 files changed, 129 insertions(+), 23 deletions(-)
> create mode 100644 include/linux/page_hinting.h
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 6b237e3..217523f 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -32,6 +32,7 @@
[...]
> #ifdef CONFIG_BALLOON_COMPACTION
> /*
> * virtballoon_migratepage - perform the balloon page migration on behalf of
> @@ -604,6 +693,13 @@ static int virtballoon_probe(struct virtio_device *vdev)
>
> virtio_device_ready(vdev);
>
> +#ifdef CONFIG_KVM_FREE_PAGE_HINTING
> + if (virtio_has_feature(vb->vdev, VIRTIO_GUEST_PAGE_HINTING_VQ)) {
> + request_hypercall = (void *)&virtballoon_page_hinting;
> + balloon_ptr = vb;
> + }
> +#endif
balloon_ptr is valid only when VIRTIO_GUEST_PAGE_HINTING_VQ is set.
So ....
> +void hyperlist_ready(int entries)
> {
> - /*
> - * Dummy function: Tobe filled later.
> - */
> - empty_hyperlist();
> trace_guest_str_dump("Hypercall to host...:");
> + request_hypercall(balloon_ptr, entries);
Should check if balloon_ptr is valid here. Otherwise, there may be
"kernel NULL pointer dereference" bug.
> + empty_hyperlist();
> }
