[QEMU Patch] virtio-baloon: Support for page hinting
From: Nitesh Narayan Lal
Date: Wed Jul 10 2019 - 15:53:43 EST
Enables QEMU to perform madvise free on the memory range reported
by the vm.
Signed-off-by: Nitesh Narayan Lal <nitesh@xxxxxxxxxx>
---
hw/virtio/trace-events | 1 +
hw/virtio/virtio-balloon.c | 59 +++++++++++++++++++
include/hw/virtio/virtio-balloon.h | 2 +-
include/qemu/osdep.h | 7 +++
.../standard-headers/linux/virtio_balloon.h | 1 +
5 files changed, 69 insertions(+), 1 deletion(-)
diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
index e28ba48da6..f703a22d36 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_balloon_hinting_request(unsigned long pfn, unsigned int num_pages) "Guest page hinting request PFN:%lu size: %d"
# 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 2112874055..5d186707b5 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -34,6 +34,9 @@
#define BALLOON_PAGE_SIZE (1 << VIRTIO_BALLOON_PFN_SHIFT)
+#define VIRTIO_BALLOON_PAGE_HINTING_MAX_PAGES 16
+void free_mem_range(uint64_t addr, uint64_t len);
+
struct PartiallyBalloonedPage {
RAMBlock *rb;
ram_addr_t base;
@@ -328,6 +331,58 @@ static void balloon_stats_set_poll_interval(Object *obj, Visitor *v,
balloon_stats_change_timer(s, 0);
}
+void free_mem_range(uint64_t addr, uint64_t len)
+{
+ int ret = 0;
+ void *hvaddr_to_free;
+ MemoryRegionSection mrs = memory_region_find(get_system_memory(),
+ addr, 1);
+ if (!mrs.mr) {
+ warn_report("%s:No memory is mapped at address 0x%lu", __func__, addr);
+ return;
+ }
+
+ if (!memory_region_is_ram(mrs.mr) && !memory_region_is_romd(mrs.mr)) {
+ warn_report("%s:Memory at address 0x%s is not RAM:0x%lu", __func__,
+ HWADDR_PRIx, addr);
+ memory_region_unref(mrs.mr);
+ return;
+ }
+
+ hvaddr_to_free = qemu_map_ram_ptr(mrs.mr->ram_block, mrs.offset_within_region);
+ trace_virtio_balloon_hinting_request(addr, len);
+ ret = qemu_madvise(hvaddr_to_free,len, QEMU_MADV_FREE);
+ if (ret == -1) {
+ warn_report("%s: Madvise failed with error:%d", __func__, ret);
+ }
+}
+
+static void virtio_balloon_handle_page_hinting(VirtIODevice *vdev,
+ VirtQueue *vq)
+{
+ VirtQueueElement *elem;
+ size_t offset = 0;
+ uint64_t gpa, len;
+ elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
+ if (!elem) {
+ return;
+ }
+ /* For pending hints which are < max_pages(16), 'gpa != 0' ensures that we
+ * only read the buffer which holds a valid PFN value.
+ * TODO: Find a better way to do this.
+ */
+ while (iov_to_buf(elem->out_sg, elem->out_num, offset, &gpa, 8) == 8 && gpa != 0) {
+ offset += 8;
+ offset += iov_to_buf(elem->out_sg, elem->out_num, offset, &len, 8);
+ if (!qemu_balloon_is_inhibited()) {
+ free_mem_range(gpa, len);
+ }
+ }
+ 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 +749,7 @@ 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 +836,7 @@ 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_handle_page_hinting);
if (virtio_has_feature(s->host_features,
VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
@@ -875,6 +932,8 @@ 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 1afafb12f6..a58b24fdf2 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, *free_page_vq, *hvq;
uint32_t free_page_report_status;
uint32_t num_pages;
uint32_t actual;
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index af2b91f0b8..bb9207e7f4 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -360,6 +360,11 @@ 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_MADV_INVALID
+#endif
#elif defined(CONFIG_POSIX_MADVISE)
@@ -373,6 +378,7 @@ 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_MADV_INVALID
#else /* no-op */
@@ -386,6 +392,7 @@ 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_MADV_INVALID
#endif
diff --git a/include/standard-headers/linux/virtio_balloon.h b/include/standard-headers/linux/virtio_balloon.h
index 9375ca2a70..f9e3e82562 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
--
2.21.0