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Re: [Qemu-devel] [PATCH v4] virtio-balloon: free pbp more aggressively
From: |
David Hildenbrand |
Subject: |
Re: [Qemu-devel] [PATCH v4] virtio-balloon: free pbp more aggressively |
Date: |
Thu, 25 Jul 2019 17:21:30 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 |
On 25.07.19 17:18, Michael S. Tsirkin wrote:
> Previous patches switched to a temporary pbp but that does not go far
> enough: after device uses a buffer, guest is free to reuse it, so
> tracking the page and freeing it later is wrong.
>
> Free and reset the pbp after we push each element.
>
> Fixes: ed48c59875b6 ("virtio-balloon: Safely handle BALLOON_PAGE_SIZE < host
> page size")
> Cc: address@hidden #v4.0.0
> Cc: David Hildenbrand <address@hidden>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> ---
>
> changes from v2, v3:
> v3 was same as v2, sent by mistake
> v4 fixes a typo
>
> hw/virtio/virtio-balloon.c | 37 ++++++++++++++++---------------------
>
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index fe9664e42c..25de154307 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -41,22 +41,19 @@ typedef struct PartiallyBalloonedPage {
>
> static void virtio_balloon_pbp_free(PartiallyBalloonedPage *pbp)
> {
> - if (!pbp) {
> + if (!pbp->bitmap) {
> return;
> }
> g_free(pbp->bitmap);
> - g_free(pbp);
> + pbp->bitmap = NULL;
> }
>
> -static PartiallyBalloonedPage *virtio_balloon_pbp_alloc(ram_addr_t base_gpa,
> - long subpages)
> +static void virtio_balloon_pbp_alloc(PartiallyBalloonedPage *pbp,
> + ram_addr_t base_gpa,
> + long subpages)
> {
> - PartiallyBalloonedPage *pbp = g_new0(PartiallyBalloonedPage, 1);
> -
> pbp->base_gpa = base_gpa;
> pbp->bitmap = bitmap_new(subpages);
> -
> - return pbp;
> }
>
> static bool virtio_balloon_pbp_matches(PartiallyBalloonedPage *pbp,
> @@ -67,7 +64,7 @@ static bool
> virtio_balloon_pbp_matches(PartiallyBalloonedPage *pbp,
>
> static void balloon_inflate_page(VirtIOBalloon *balloon,
> MemoryRegion *mr, hwaddr mr_offset,
> - PartiallyBalloonedPage **pbp)
> + PartiallyBalloonedPage *pbp)
> {
> void *addr = memory_region_get_ram_ptr(mr) + mr_offset;
> ram_addr_t rb_offset, rb_aligned_offset, base_gpa;
> @@ -104,22 +101,21 @@ static void balloon_inflate_page(VirtIOBalloon *balloon,
> base_gpa = memory_region_get_ram_addr(mr) + mr_offset -
> (rb_offset - rb_aligned_offset);
>
> - if (*pbp && !virtio_balloon_pbp_matches(*pbp, base_gpa)) {
> + if (pbp->bitmap && !virtio_balloon_pbp_matches(pbp, base_gpa)) {
> /* We've partially ballooned part of a host page, but now
> * we're trying to balloon part of a different one. Too hard,
> * give up on the old partial page */
> - virtio_balloon_pbp_free(*pbp);
> - *pbp = NULL;
> + virtio_balloon_pbp_free(pbp);
> }
>
> - if (!*pbp) {
> - *pbp = virtio_balloon_pbp_alloc(base_gpa, subpages);
> + if (!pbp->bitmap) {
> + virtio_balloon_pbp_alloc(pbp, base_gpa, subpages);
> }
>
> set_bit((rb_offset - rb_aligned_offset) / BALLOON_PAGE_SIZE,
> - (*pbp)->bitmap);
> + pbp->bitmap);
>
> - if (bitmap_full((*pbp)->bitmap, subpages)) {
> + if (bitmap_full(pbp->bitmap, subpages)) {
> /* We've accumulated a full host page, we can actually discard
> * it now */
>
> @@ -127,8 +123,7 @@ static void balloon_inflate_page(VirtIOBalloon *balloon,
> /* We ignore errors from ram_block_discard_range(), because it
> * has already reported them, and failing to discard a balloon
> * page is not fatal */
> - virtio_balloon_pbp_free(*pbp);
> - *pbp = NULL;
> + virtio_balloon_pbp_free(pbp);
> }
> }
>
> @@ -328,13 +323,14 @@ static void balloon_stats_set_poll_interval(Object
> *obj, Visitor *v,
> static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
> {
> VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
> - PartiallyBalloonedPage *pbp = NULL;
> VirtQueueElement *elem;
> MemoryRegionSection section;
>
> for (;;) {
> + PartiallyBalloonedPage pbp = {};
> size_t offset = 0;
> uint32_t pfn;
> +
> elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
> if (!elem) {
> break;
> @@ -379,9 +375,8 @@ static void virtio_balloon_handle_output(VirtIODevice
> *vdev, VirtQueue *vq)
> virtqueue_push(vq, elem, offset);
> virtio_notify(vdev, vq);
> g_free(elem);
> + virtio_balloon_pbp_free(&pbp);
> }
> -
> - virtio_balloon_pbp_free(pbp);
> }
>
> static void virtio_balloon_receive_stats(VirtIODevice *vdev, VirtQueue *vq)
>
Works with hugetlbfs on x86 and LGTM:
Reviewed-by: David Hildenbrand <address@hidden>
--
Thanks,
David / dhildenb