Hi Nitesh,
>
> This patch enables QEMU to handle page hinting requests
> from the guest. Once the guest kicks QEMU to free a page,
> QEMU retrives the guest physical address and converts it to
> host virtual address and then MADVISE that memory.
>
> Signed-off-by: Nitesh Narayan Lal <nilal@xxxxxxxxxx>
> ---
> hw/virtio/virtio-balloon.c | 81
> ++++++++++++++++++++++++++++++++++++++
> hw/virtio/virtio.c | 24 +++++++++++
> include/hw/virtio/virtio-access.h | 1 +
> include/hw/virtio/virtio-balloon.h | 2 +-
> include/qemu/osdep.h | 7 ++++
> 5 files changed, 114 insertions(+), 1 deletion(-)
>
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index 37cde38..de10350 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -33,6 +33,8 @@
>
> #define BALLOON_PAGE_SIZE (1 << VIRTIO_BALLOON_PFN_SHIFT)
>
> +void page_hinting_request(uint64_t addr, uint32_t len);
> +
> static void balloon_page(void *addr, int deflate)
> {
> if (!qemu_balloon_is_inhibited() && (!kvm_enabled() ||
> @@ -205,6 +207,84 @@ static void balloon_stats_set_poll_interval(Object *obj,
> Visitor *v,
> balloon_stats_change_timer(s, 0);
> }
>
> +static void *gpa2hva(MemoryRegion **p_mr, hwaddr addr, Error **errp)
> +{
> + MemoryRegionSection mrs = memory_region_find(get_system_memory(),
> + addr, 1);
> +
> + if (!mrs.mr) {
> + error_setg(errp, "No memory is mapped at address 0x%" HWADDR_PRIx,
> addr);
> + return NULL;
> + }
> +
> + if (!memory_region_is_ram(mrs.mr) && !memory_region_is_romd(mrs.mr)) {
> + error_setg(errp, "Memory at address 0x%" HWADDR_PRIx "is not RAM",
> addr);
> + memory_region_unref(mrs.mr);
> + return NULL;
> + }
> +
> + *p_mr = mrs.mr;
> + return qemu_map_ram_ptr(mrs.mr->ram_block, mrs.offset_within_region);
> +}
> +
> +struct guest_pages {
> + unsigned long pfn;
> + unsigned int pages;
> +};
> +
> +
> +void page_hinting_request(uint64_t addr, uint32_t len)
> +{
> + Error *local_err = NULL;
> + MemoryRegion *mr = NULL;
> + void *hvaddr;
> + int ret = 0;
> + struct guest_pages *guest_obj;
> + int i = 0;
> + void *hvaddr_to_free;
> + unsigned long pfn, pfn_end;
> + uint64_t gpaddr_to_free;
> +
> + /*ptr is the host physical address*/
Could not understand the comment?
> + hvaddr = gpa2hva(&mr, addr, &local_err);
> + if (local_err) {
> + error_report_err(local_err);
> + return;
> + }
> + guest_obj = hvaddr;
> +
> + while (i < len) {
> + pfn = guest_obj[i].pfn;
> + pfn_end = guest_obj[i].pfn + guest_obj[i].pages - 1;
> + while (pfn <= pfn_end) {
> + gpaddr_to_free = pfn << VIRTIO_BALLOON_PFN_SHIFT;
> + hvaddr_to_free = gpa2hva(&mr, gpaddr_to_free, &local_err);
> + if (local_err) {
> + error_report_err(local_err);
> + return;
> + }
> + ret = qemu_madvise((void *)hvaddr_to_free, 4096, QEMU_MADV_FREE);
> + if (ret == -1)
> + printf("\n%d:%s Error: Madvise failed with error:%d\n", __LINE__,
> __func__, ret);
> + pfn++;
> + }
> + i++;
> + }
> +}
> +
> +
> +static void virtio_balloon_page_hinting(VirtIODevice *vdev, VirtQueue *vq)
> +{
> + uint64_t addr;
> + uint32_t len;
> + VirtQueueElement elem = {};
> +
> + pop_hinting_addr(vq, &addr, &len);
> + page_hinting_request(addr, len);
> + virtqueue_push(vq, &elem, 0);
> + virtio_notify(vdev, vq);
> +}
> +
> static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
> {
> VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
> @@ -443,6 +523,7 @@ static void virtio_balloon_device_realize(DeviceState
> *dev, Error **errp)
> s->ivq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
> s->dvq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
> s->svq = virtio_add_queue(vdev, 128, virtio_balloon_receive_stats);
> + s->hvq = virtio_add_queue(vdev, 128, virtio_balloon_page_hinting);
>
> reset_stats(s);
> }
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 311929e..24e26ec 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -825,6 +825,30 @@ static void *virtqueue_alloc_element(size_t sz, unsigned
> out_num, unsigned in_nu
> return elem;
> }
>
> +void pop_hinting_addr(VirtQueue *vq, uint64_t *addr, uint32_t *len)
> +{
> + VRingMemoryRegionCaches *caches;
> + VRingDesc desc;
> + MemoryRegionCache *desc_cache;
> + VirtIODevice *vdev = vq->vdev;
> + unsigned int head, i, max;
> +
> + max = vq->vring.num;
> + if (!virtqueue_get_head(vq, vq->last_avail_idx++, &head)) {
> + printf("\n%d:%sError: Unable to read head\n", __LINE__, __func__);
> + }
> + i = head;
we can avoid 'i' here and directly pass head
'to vring_desc_read' function?
> +
> + caches = vring_get_region_caches(vq);
> + if (caches->desc.len < max * sizeof(VRingDesc)) {
> + virtio_error(vdev, "Cannot map descriptor ring");
> + }
> + desc_cache = &caches->desc;
> + vring_desc_read(vdev, &desc, desc_cache, i);
> + *addr = desc.addr;
> + *len = desc.len;
> +}
> +
> void *virtqueue_pop(VirtQueue *vq, size_t sz)
> {
> unsigned int i, head, max;
> diff --git a/include/hw/virtio/virtio-access.h
> b/include/hw/virtio/virtio-access.h
> index 2e92074..568d71f 100644
> --- a/include/hw/virtio/virtio-access.h
> +++ b/include/hw/virtio/virtio-access.h
> @@ -24,6 +24,7 @@
> #define LEGACY_VIRTIO_IS_BIENDIAN 1
> #endif
>
> +void pop_hinting_addr(VirtQueue *vq, uint64_t *addr, uint32_t *len);
> static inline bool virtio_access_is_big_endian(VirtIODevice *vdev)
> {
> #if defined(LEGACY_VIRTIO_IS_BIENDIAN)
> diff --git a/include/hw/virtio/virtio-balloon.h
> b/include/hw/virtio/virtio-balloon.h
> index 1ea13bd..dfb5782 100644
> --- a/include/hw/virtio/virtio-balloon.h
> +++ b/include/hw/virtio/virtio-balloon.h
> @@ -33,7 +33,7 @@ typedef struct virtio_balloon_stat_modern {
>
> typedef struct VirtIOBalloon {
> VirtIODevice parent_obj;
> - VirtQueue *ivq, *dvq, *svq;
> + VirtQueue *ivq, *dvq, *svq, *hvq;
> uint32_t num_pages;
> uint32_t actual;
> uint64_t stats[VIRTIO_BALLOON_S_NR];
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 9dd318a..033d64c 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -278,6 +278,11 @@ void qemu_anon_ram_free(void *ptr, size_t size);
> #else
> #define QEMU_MADV_REMOVE QEMU_MADV_INVALID
> #endif
> +#ifdef MADV_FREE
> +#define QEMU_MADV_FREE MADV_FREE
> +#else
> +#define QEMU_MADV_FREE QEMU_MAD_INVALID
> +#endif
>
> #elif defined(CONFIG_POSIX_MADVISE)
>
> @@ -291,6 +296,7 @@ void qemu_anon_ram_free(void *ptr, size_t size);
> #define QEMU_MADV_HUGEPAGE QEMU_MADV_INVALID
> #define QEMU_MADV_NOHUGEPAGE QEMU_MADV_INVALID
> #define QEMU_MADV_REMOVE QEMU_MADV_INVALID
> +#define QEMU_MADV_FREE QEMU_MAD_INVALID
>
> #else /* no-op */
>
> @@ -304,6 +310,7 @@ void qemu_anon_ram_free(void *ptr, size_t size);
> #define QEMU_MADV_HUGEPAGE QEMU_MADV_INVALID
> #define QEMU_MADV_NOHUGEPAGE QEMU_MADV_INVALID
> #define QEMU_MADV_REMOVE QEMU_MADV_INVALID
> +#define QEMU_MADV_FREE QEMU_MAD_INVALID
>
> #endif
>
> --
> 2.9.4
>
>
