[QEMU Patch] virtio-baloon: Support for page hinting

[Nitesh Narayan Lal <nitesh@redhat.com>]

Enables QEMU to perform madvise free on the memory range reported
by the vm.

Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com>
---
 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