[RFC QEMU PATCH] QEMU: Provide a interface for hinting based off of the balloon infrastructure

Alexander Duyck
2019-05-30T21:57:22Z

So this is meant to be a simplification of the existing balloon interface
to use for providing hints to what memory needs to be freed. I am assuming
this is safe to do as the deflate logic does not actually appear to do very
much other than tracking what subpages have been released and which ones
haven't.

I suspect this is still a bit crude and will need some more work.
Suggestions welcome.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
hw/virtio/trace-events | 1
hw/virtio/virtio-balloon.c | 85 +++++++++++++++++++++++
include/hw/virtio/virtio-balloon.h | 2 -
include/standard-headers/linux/virtio_balloon.h | 1
4 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
index e28ba48da621..b56daf460769 100644
--- a/hw/virtio/trace-events
+++ b/hw/virtio/trace-events
@@ -46,6 +46,7 @@ virtio_balloon_handle_output(const char *name, uint64_t gpa) "section name: %s g
virtio_balloon_get_config(uint32_t num_pages, uint32_t actual) "num_pages: %d actual: %d"
virtio_balloon_set_config(uint32_t actual, uint32_t oldactual) "actual: %d oldactual: %d"
virtio_balloon_to_target(uint64_t target, uint32_t num_pages) "balloon target: 0x%"PRIx64" num_pages: %d"
+virtio_bubble_handle_output(const char *name, uint64_t gpa, uint64_t size) "section name: %s gpa: 0x%" PRIx64 " size: %" PRIx64

# virtio-mmio.c
virtio_mmio_read(uint64_t offset) "virtio_mmio_read offset 0x%" PRIx64
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index 2112874055fb..eb819ec8f436 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -34,6 +34,13 @@

#define BALLOON_PAGE_SIZE (1 << VIRTIO_BALLOON_PFN_SHIFT)

+struct guest_pages {
+ unsigned long pfn;
+ unsigned int order;
+};
+
+void page_hinting_request(uint64_t addr, uint32_t len);
+
struct PartiallyBalloonedPage {
RAMBlock *rb;
ram_addr_t base;
@@ -328,6 +335,80 @@ static void balloon_stats_set_poll_interval(Object *obj, Visitor *v,
balloon_stats_change_timer(s, 0);
}

+static void bubble_inflate_page(VirtIOBalloon *balloon,
+ MemoryRegion *mr, hwaddr offset, size_t size)
+{
+ void *addr = memory_region_get_ram_ptr(mr) + offset;
+ ram_addr_t ram_offset;
+ size_t rb_page_size;
+ RAMBlock *rb;
+
+ rb = qemu_ram_block_from_host(addr, false, &ram_offset);
+ rb_page_size = qemu_ram_pagesize(rb);
+
+ /* For now we will simply ignore unaligned memory regions */
+ if ((ram_offset | size) & (rb_page_size - 1))
+ return;
+
+ ram_block_discard_range(rb, ram_offset, size);
+}
+
+static void virtio_bubble_handle_output(VirtIODevice *vdev, VirtQueue *vq)
+{
+ VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
+ VirtQueueElement *elem;
+ MemoryRegionSection section;
+
+ for (;;) {
+ size_t offset = 0;
+ struct {
+ uint32_t pfn;
+ uint32_t size;
+ } hint;
+
+ elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
+ if (!elem) {
+ return;
+ }
+
+ while (iov_to_buf(elem->out_sg, elem->out_num, offset, &hint, 8) == 8) {
+ size_t size = virtio_ldl_p(vdev, &hint.size);
+ hwaddr pa = virtio_ldl_p(vdev, &hint.pfn);
+
+ offset += 8;
+
+ if (qemu_balloon_is_inhibited())
+ continue;
+
+ pa <<= VIRTIO_BALLOON_PFN_SHIFT;
+ size <<= VIRTIO_BALLOON_PFN_SHIFT;
+
+ section = memory_region_find(get_system_memory(), pa, size);
+ if (!section.mr) {
+ trace_virtio_balloon_bad_addr(pa);
+ continue;
+ }
+
+ if (!memory_region_is_ram(section.mr) ||
+ memory_region_is_rom(section.mr) ||
+ memory_region_is_romd(section.mr)) {
+ trace_virtio_balloon_bad_addr(pa);
+ } else {
+ trace_virtio_bubble_handle_output(memory_region_name(section.mr),
+ pa, size);
+ bubble_inflate_page(s, section.mr,
+ section.offset_within_region, size);
+ }
+
+ memory_region_unref(section.mr);
+ }
+
+ virtqueue_push(vq, elem, offset);
+ virtio_notify(vdev, vq);
+ g_free(elem);
+ }
+}
+
static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
{
VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
@@ -694,6 +775,7 @@ static uint64_t virtio_balloon_get_features(VirtIODevice *vdev, uint64_t f,
VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
f |= dev->host_features;
virtio_add_feature(&f, VIRTIO_BALLOON_F_STATS_VQ);
+ virtio_add_feature(&f, VIRTIO_BALLOON_F_HINTING);

return f;
}
@@ -780,6 +862,7 @@ 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_bubble_handle_output);

if (virtio_has_feature(s->host_features,
VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
@@ -875,6 +958,8 @@ static void virtio_balloon_instance_init(Object *obj)

object_property_add(obj, "guest-stats", "guest statistics",
balloon_stats_get_all, NULL, NULL, s, NULL);
+ object_property_add(obj, "guest-page-hinting", "guest page hinting",
+ NULL, NULL, NULL, s, NULL);

object_property_add(obj, "guest-stats-polling-interval", "int",
balloon_stats_get_poll_interval,
diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h
index 1afafb12f6bc..dd6d4d0e45fd 100644
--- a/include/hw/virtio/virtio-balloon.h
+++ b/include/hw/virtio/virtio-balloon.h
@@ -44,7 +44,7 @@ enum virtio_balloon_free_page_report_status {

typedef struct VirtIOBalloon {
VirtIODevice parent_obj;
- VirtQueue *ivq, *dvq, *svq, *free_page_vq;
+ VirtQueue *ivq, *dvq, *svq, *hvq, *free_page_vq;
uint32_t free_page_report_status;
uint32_t num_pages;
uint32_t actual;
diff --git a/include/standard-headers/linux/virtio_balloon.h b/include/standard-headers/linux/virtio_balloon.h
index 9375ca2a70de..f9e3e8256261 100644
--- a/include/standard-headers/linux/virtio_balloon.h
+++ b/include/standard-headers/linux/virtio_balloon.h
@@ -36,6 +36,7 @@
#define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */
#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_HINTING 5 /* Page hinting virtqueue */

/* Size of a PFN in the balloon interface. */
#define VIRTIO_BALLOON_PFN_SHIFT 12