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Re: [PATCH v19 QEMU 3/4] virtio-balloon: Provide an interface for free p
From: |
David Hildenbrand |
Subject: |
Re: [PATCH v19 QEMU 3/4] virtio-balloon: Provide an interface for free page reporting |
Date: |
Wed, 15 Apr 2020 10:17:50 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 |
On 10.04.20 05:41, Alexander Duyck wrote:
> From: Alexander Duyck <address@hidden>
>
> Add support for free page reporting. The idea is to function very similar
> to how the balloon works in that we basically end up madvising the page as
> not being used. However we don't really need to bother with any deflate
> type logic since the page will be faulted back into the guest when it is
> read or written to.
>
> This provides a new way of letting the guest proactively report free
> pages to the hypervisor, so the hypervisor can reuse them. In contrast to
> inflate/deflate that is triggered via the hypervisor explicitly.
Much better, thanks!
>
> Signed-off-by: Alexander Duyck <address@hidden>
> ---
> hw/virtio/virtio-balloon.c | 63
> +++++++++++++++++++++++++++++++++++-
> include/hw/virtio/virtio-balloon.h | 2 +
> 2 files changed, 62 insertions(+), 3 deletions(-)
>
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index 1c6d36a29a04..86d8b48a8e3a 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -321,6 +321,57 @@ static void balloon_stats_set_poll_interval(Object *obj,
> Visitor *v,
> balloon_stats_change_timer(s, 0);
> }
>
> +static void virtio_balloon_handle_report(VirtIODevice *vdev, VirtQueue *vq)
> +{
> + VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
> + VirtQueueElement *elem;
> +
> + while ((elem = virtqueue_pop(vq, sizeof(VirtQueueElement)))) {
> + unsigned int i;
> +
> + for (i = 0; i < elem->in_num; i++) {
> + void *addr = elem->in_sg[i].iov_base;
> + size_t size = elem->in_sg[i].iov_len;
> + ram_addr_t ram_offset;
> + size_t rb_page_size;
> + RAMBlock *rb;
> +
> + if (qemu_balloon_is_inhibited() || dev->poison_val) {
> + continue;
actually, you want to do that in the outer loop, no?
> + }
> +
> + /*
> + * There is no need to check the memory section to see if
> + * it is ram/readonly/romd like there is for handle_output
> + * below. If the region is not meant to be written to then
> + * address_space_map will have allocated a bounce buffer
> + * and it will be freed in address_space_unmap and trigger
> + * and unassigned_mem_write before failing to copy over the
> + * buffer. If more than one bad descriptor is provided it
> + * will return NULL after the first bounce buffer and fail
> + * to map any resources.
> + */
> + rb = qemu_ram_block_from_host(addr, false, &ram_offset);
> + if (!rb) {
> + trace_virtio_balloon_bad_addr(elem->in_addr[i]);
> + continue;
> + }
> +
> + /* For now we will simply ignore unaligned memory regions */
> + rb_page_size = qemu_ram_pagesize(rb);
> + if (!QEMU_IS_ALIGNED(ram_offset | size, rb_page_size)) {
/me thinks you can drop rb_page_size
I *think* there is still one remaining case to handle: Crossing RAM blocks.
Most probably you should check
/* For now, ignore crossing RAM blocks. */
if (ram_offset + size >= qemu_ram_get_used_length()) {
continue;
}
otherwise ram_block_discard_range() will report an error.
--
Thanks,
David / dhildenb
- Re: [PATCH v19 QEMU 1/4] virtio-balloon: Implement support for page poison tracking feature, (continued)
- Re: [PATCH v19 QEMU 1/4] virtio-balloon: Implement support for page poison tracking feature, David Hildenbrand, 2020/04/15
- Re: [PATCH v19 QEMU 1/4] virtio-balloon: Implement support for page poison tracking feature, Alexander Duyck, 2020/04/15
- Re: [PATCH v19 QEMU 1/4] virtio-balloon: Implement support for page poison tracking feature, David Hildenbrand, 2020/04/16
- Re: [PATCH v19 QEMU 1/4] virtio-balloon: Implement support for page poison tracking feature, David Hildenbrand, 2020/04/16
- Re: [PATCH v19 QEMU 1/4] virtio-balloon: Implement support for page poison tracking feature, Michael S. Tsirkin, 2020/04/16
- Re: [PATCH v19 QEMU 1/4] virtio-balloon: Implement support for page poison tracking feature, David Hildenbrand, 2020/04/16
- Re: [PATCH v19 QEMU 1/4] virtio-balloon: Implement support for page poison tracking feature, Alexander Duyck, 2020/04/16
- Re: [PATCH v19 QEMU 1/4] virtio-balloon: Implement support for page poison tracking feature, David Hildenbrand, 2020/04/16
[PATCH v19 QEMU 2/4] linux-headers: update to contain virito-balloon free page reporting, Alexander Duyck, 2020/04/09
[PATCH v19 QEMU 3/4] virtio-balloon: Provide an interface for free page reporting, Alexander Duyck, 2020/04/09
- Re: [PATCH v19 QEMU 3/4] virtio-balloon: Provide an interface for free page reporting,
David Hildenbrand <=
[PATCH v19 QEMU 4/4] memory: Do not allow direct write access to rom_device regions, Alexander Duyck, 2020/04/09