On 16.04.20 21:30, Alexander Duyck wrote:
> From: Alexander Duyck <[email protected]>
>
> If we have free page hinting or page reporting enabled we should disable it
> if the pages are poisoned or initialized on free and we cannot notify the
> hypervisor.
>
Please split that up into an actual fix (Fixes:) for free page reporting
and an optimization for free page hinting. Also, please document why we
are doing stuff.
Regarding the free page reporting part, I propose something like this instead
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 0ef16566c3f3..9b1e56da1e29 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -1107,6 +1107,20 @@ static int virtballoon_restore(struct virtio_device
*vdev)
static int virtballoon_validate(struct virtio_device *vdev)
{
+ /*
+ * Free page reporting relies on the fact that any access after
+ * pages were reported (esp. from the buddy) will result in them getting
+ * deflated automatically. In case we care about the page content, we
+ * need support from the hypervisor to provide us with the same page
+ * (poisoned) content we originally had in the page. Without
+ * VIRTIO_BALLOON_F_PAGE_POISON, we will receive either the original
+ * page or a zeroed page.
+ */
+ if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON) &&
+ !IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) &&
+ page_poisoning_enabled())
+ __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);
+
/* Tell the host whether we care about poisoned pages. */
if (!want_init_on_free() &&
(IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) ||
> Fixes: 5d757c8d518d ("virtio-balloon: add support for providing free page
> reports to host")
>
> Signed-off-by: Alexander Duyck <[email protected]>
> ---
> drivers/virtio/virtio_balloon.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 95d9c2f0a7be..08bc86a6e468 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -1110,8 +1110,12 @@ static int virtballoon_validate(struct virtio_device
> *vdev)
> /* Tell the host whether we care about poisoned pages. */
> if (!want_init_on_free() &&
> (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) ||
> - !page_poisoning_enabled()))
> + !page_poisoning_enabled())) {
> __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
> + } else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
> + __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT);
> + __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);
> + }
>
> __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
> return 0;
>
--
Thanks,
David / dhildenb
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