> 2020年7月16日 14:43，Michael S. Tsirkin <mst@xxxxxxxxxx> 写道： > > On Thu, Jul 16, 2020 at 10:41:51AM +0800, Hui Zhu wrote: >> diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h >> index dc3e656..4d0151a 100644 >> --- a/include/uapi/linux/virtio_balloon.h >> +++ b/include/uapi/linux/virtio_balloon.h >> @@ -37,6 +37,7 @@ >> #define VIRTIO_BALLOON_F_FREE_PAGE_HINT 3 /* VQ to report free pages */ >> #define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */ >> #define VIRTIO_BALLOON_F_REPORTING 5 /* Page reporting virtqueue */ >> +#define VIRTIO_BALLOON_F_CONT_PAGES 6 /* VQ to report continuous pages */ >> >> /* Size of a PFN in the balloon interface. */ >> #define VIRTIO_BALLOON_PFN_SHIFT 12 > > So how does the guest/host interface look like? > Could you write up something about it? Continuous pages are report by num_pfns and pfns in virtio_balloon too. The function to set pfns is set_page_pfns_size in https://github.com/teawater/linux/blob/balloon_conts/drivers/virtio/virtio_balloon.c#L221 static void set_page_pfns_size(struct virtio_balloon *vb, __virtio32 pfns[], struct page *page, size_t size) { /* Set the first pfn of the continuous pages. */ pfns[0] = cpu_to_virtio32(vb->vdev, page_to_balloon_pfn(page)); /* Set the size of the continuous pages. */ pfns[1] = (__virtio32) size; } Each of continuous pages need 2 pfn. The first pfn of the pages is set to pfns[0]. The size of the pages is set to pfns[1]. The pfn is 32 bits. So the max order of inflate continuous pages is VIRTIO_BALLOON_INFLATE_MAX_ORDER. #define VIRTIO_BALLOON_INFLATE_MAX_ORDER min((int) (sizeof(__virtio32) * BITS_PER_BYTE - \ 1 - PAGE_SHIFT), (MAX_ORDER-1)) The max page number of deflate continuous pages is VIRTIO_BALLOON_DEFLATE_MAX_PAGES_NUM. #define VIRTIO_BALLOON_DEFLATE_MAX_PAGES_NUM (((__virtio32)~0U) >> PAGE_SHIFT) Best, Hui
