Drivers: hv: balloon: Implement hot-add functionality

Implement the memory hot-add functionality. With this, Linux guests can fully
participate in the Dynamic Memory protocol implemented in the Windows hosts.

In this version of the patch, based Olaf Herring's feedback, I have gotten
rid of the module level dependency on MEMORY_HOTPLUG. Instead the code within
the driver that depends on MEMORY_HOTPLUG has the appropriate compilation
switches. This would allow this driver to support pure ballooning in cases
where the kernel does not support memory hotplug.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 387 insertions, 21 deletions

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 4743db9e5f34..2cf7d4e964bd 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -412,6 +412,27 @@ struct dm_info_msg {
  * End protocol definitions.
  */
 
+/*
+ * State to manage hot adding memory into the guest.
+ * The range start_pfn : end_pfn specifies the range
+ * that the host has asked us to hot add. The range
+ * start_pfn : ha_end_pfn specifies the range that we have
+ * currently hot added. We hot add in multiples of 128M
+ * chunks; it is possible that we may not be able to bring
+ * online all the pages in the region. The range
+ * covered_start_pfn : covered_end_pfn defines the pages that can
+ * be brough online.
+ */
+
+struct hv_hotadd_state {
+        struct list_head list;
+        unsigned long start_pfn;
+        unsigned long covered_start_pfn;
+        unsigned long covered_end_pfn;
+        unsigned long ha_end_pfn;
+        unsigned long end_pfn;
+};
+
 struct balloon_state {
         __u32 num_pages;
         struct work_struct wrk;
@@ -419,16 +440,17 @@ struct balloon_state {
 
 struct hot_add_wrk {
         union dm_mem_page_range ha_page_range;
+        union dm_mem_page_range ha_region_range;
         struct work_struct wrk;
 };
 
-static bool hot_add;
+static bool hot_add = true;
 static bool do_hot_add;
 /*
  * Delay reporting memory pressure by
  * the specified number of seconds.
  */
-static uint pressure_report_delay = 30;
+static uint pressure_report_delay = 45;
 
 module_param(hot_add, bool, (S_IRUGO | S_IWUSR));
 MODULE_PARM_DESC(hot_add, "If set attempt memory hot_add");
@@ -456,6 +478,7 @@ enum hv_dm_state {
 static __u8 recv_buffer[PAGE_SIZE];
 static __u8 *send_buffer;
 #define PAGES_IN_2M     512
+#define HA_CHUNK (32 * 1024)
 
 struct hv_dynmem_device {
         struct hv_device *dev;
@@ -479,6 +502,17 @@ struct hv_dynmem_device {
         struct hot_add_wrk ha_wrk;
 
         /*
+         * This state tracks if the host has specified a hot-add
+         * region.
+         */
+        bool host_specified_ha_region;
+
+        /*
+         * State to synchronize hot-add.
+         */
+        struct completion  ol_waitevent;
+        bool ha_waiting;
+        /*
          * This thread handles hot-add
          * requests from the host as well as notifying
          * the host with regards to memory pressure in
@@ -487,6 +521,11 @@ struct hv_dynmem_device {
         struct task_struct *thread;
 
         /*
+         * A list of hot-add regions.
+         */
+        struct list_head ha_region_list;
+
+        /*
          * We start with the highest version we can support
          * and downgrade based on the host; we save here the
          * next version to try.
@@ -496,35 +535,329 @@ struct hv_dynmem_device {
 
 static struct hv_dynmem_device dm_device;
 
-static void hot_add_req(struct work_struct *dummy)
+#ifdef CONFIG_MEMORY_HOTPLUG
+
+void hv_bring_pgs_online(unsigned long start_pfn, unsigned long size)
 {
+        int i;
 
-        struct dm_hot_add_response resp;
+        for (i = 0; i < size; i++) {
+                struct page *pg;
+                pg = pfn_to_page(start_pfn + i);
+                __online_page_set_limits(pg);
+                __online_page_increment_counters(pg);
+                __online_page_free(pg);
+        }
+}
+
+static void hv_mem_hot_add(unsigned long start, unsigned long size,
+                                unsigned long pfn_count,
+                                struct hv_hotadd_state *has)
+{
+        int ret = 0;
+        int i, nid, t;
+        unsigned long start_pfn;
+        unsigned long processed_pfn;
+        unsigned long total_pfn = pfn_count;
+
+        for (i = 0; i < (size/HA_CHUNK); i++) {
+                start_pfn = start + (i * HA_CHUNK);
+                has->ha_end_pfn +=  HA_CHUNK;
+
+                if (total_pfn > HA_CHUNK) {
+                        processed_pfn = HA_CHUNK;
+                        total_pfn -= HA_CHUNK;
+                } else {
+                        processed_pfn = total_pfn;
+                        total_pfn = 0;
+                }
+
+                has->covered_end_pfn +=  processed_pfn;
 
-        if (do_hot_add) {
+                init_completion(&dm_device.ol_waitevent);
+                dm_device.ha_waiting = true;
 
-                pr_info("Memory hot add not supported\n");
+                nid = memory_add_physaddr_to_nid(PFN_PHYS(start_pfn));
+                ret = add_memory(nid, PFN_PHYS((start_pfn)),
+                                (HA_CHUNK << PAGE_SHIFT));
+
+                if (ret) {
+                        pr_info("hot_add memory failed error is %d\n", ret);
+                        has->ha_end_pfn -= HA_CHUNK;
+                        has->covered_end_pfn -=  processed_pfn;
+                        break;
+                }
 
                 /*
-                 * Currently we do not support hot add.
-                 * Just fail the request.
+                 * Wait for the memory block to be onlined.
                  */
+                t = wait_for_completion_timeout(&dm_device.ol_waitevent, 5*HZ);
+                if (t == 0) {
+                        pr_info("hot_add memory timedout\n");
+                        has->ha_end_pfn -= HA_CHUNK;
+                        has->covered_end_pfn -=  processed_pfn;
+                        break;
+                }
+
         }
 
+        return;
+}
+
+static void hv_online_page(struct page *pg)
+{
+        struct list_head *cur;
+        struct hv_hotadd_state *has;
+        unsigned long cur_start_pgp;
+        unsigned long cur_end_pgp;
+
+        if (dm_device.ha_waiting) {
+                dm_device.ha_waiting = false;
+                complete(&dm_device.ol_waitevent);
+        }
+
+        list_for_each(cur, &dm_device.ha_region_list) {
+                has = list_entry(cur, struct hv_hotadd_state, list);
+                cur_start_pgp = (unsigned long)
+                                pfn_to_page(has->covered_start_pfn);
+                cur_end_pgp = (unsigned long)pfn_to_page(has->covered_end_pfn);
+
+                if (((unsigned long)pg >= cur_start_pgp) &&
+                        ((unsigned long)pg < cur_end_pgp)) {
+                        /*
+                         * This frame is currently backed; online the
+                         * page.
+                         */
+                        __online_page_set_limits(pg);
+                        __online_page_increment_counters(pg);
+                        __online_page_free(pg);
+                        has->covered_start_pfn++;
+                }
+        }
+}
+
+static bool pfn_covered(unsigned long start_pfn, unsigned long pfn_cnt)
+{
+        struct list_head *cur;
+        struct hv_hotadd_state *has;
+        unsigned long residual, new_inc;
+
+        if (list_empty(&dm_device.ha_region_list))
+                return false;
+
+        list_for_each(cur, &dm_device.ha_region_list) {
+                has = list_entry(cur, struct hv_hotadd_state, list);
+
+                /*
+                 * If the pfn range we are dealing with is not in the current
+                 * "hot add block", move on.
+                 */
+                if ((start_pfn >= has->end_pfn))
+                        continue;
+                /*
+                 * If the current hot add-request extends beyond
+                 * our current limit; extend it.
+                 */
+                if ((start_pfn + pfn_cnt) > has->end_pfn) {
+                        residual = (start_pfn + pfn_cnt - has->end_pfn);
+                        /*
+                         * Extend the region by multiples of HA_CHUNK.
+                         */
+                        new_inc = (residual / HA_CHUNK) * HA_CHUNK;
+                        if (residual % HA_CHUNK)
+                                new_inc += HA_CHUNK;
+
+                        has->end_pfn += new_inc;
+                }
+
+                /*
+                 * If the current start pfn is not where the covered_end
+                 * is, update it.
+                 */
+
+                if (has->covered_end_pfn != start_pfn) {
+                        has->covered_end_pfn = start_pfn;
+                        has->covered_start_pfn = start_pfn;
+                }
+                return true;
+
+        }
+
+        return false;
+}
+
+static unsigned long handle_pg_range(unsigned long pg_start,
+                                        unsigned long pg_count)
+{
+        unsigned long start_pfn = pg_start;
+        unsigned long pfn_cnt = pg_count;
+        unsigned long size;
+        struct list_head *cur;
+        struct hv_hotadd_state *has;
+        unsigned long pgs_ol = 0;
+        unsigned long old_covered_state;
+
+        if (list_empty(&dm_device.ha_region_list))
+                return 0;
+
+        list_for_each(cur, &dm_device.ha_region_list) {
+                has = list_entry(cur, struct hv_hotadd_state, list);
+
+                /*
+                 * If the pfn range we are dealing with is not in the current
+                 * "hot add block", move on.
+                 */
+                if ((start_pfn >= has->end_pfn))
+                        continue;
+
+                old_covered_state = has->covered_end_pfn;
+
+                if (start_pfn < has->ha_end_pfn) {
+                        /*
+                         * This is the case where we are backing pages
+                         * in an already hot added region. Bring
+                         * these pages online first.
+                         */
+                        pgs_ol = has->ha_end_pfn - start_pfn;
+                        if (pgs_ol > pfn_cnt)
+                                pgs_ol = pfn_cnt;
+                        hv_bring_pgs_online(start_pfn, pgs_ol);
+                        has->covered_end_pfn +=  pgs_ol;
+                        has->covered_start_pfn +=  pgs_ol;
+                        pfn_cnt -= pgs_ol;
+                }
+
+                if ((has->ha_end_pfn < has->end_pfn) && (pfn_cnt > 0)) {
+                        /*
+                         * We have some residual hot add range
+                         * that needs to be hot added; hot add
+                         * it now. Hot add a multiple of
+                         * of HA_CHUNK that fully covers the pages
+                         * we have.
+                         */
+                        size = (has->end_pfn - has->ha_end_pfn);
+                        if (pfn_cnt <= size) {
+                                size = ((pfn_cnt / HA_CHUNK) * HA_CHUNK);
+                                if (pfn_cnt % HA_CHUNK)
+                                        size += HA_CHUNK;
+                        } else {
+                                pfn_cnt = size;
+                        }
+                        hv_mem_hot_add(has->ha_end_pfn, size, pfn_cnt, has);
+                }
+                /*
+                 * If we managed to online any pages that were given to us,
+                 * we declare success.
+                 */
+                return has->covered_end_pfn - old_covered_state;
+
+        }
+
+        return 0;
+}
+
+static unsigned long process_hot_add(unsigned long pg_start,
+                                        unsigned long pfn_cnt,
+                                        unsigned long rg_start,
+                                        unsigned long rg_size)
+{
+        struct hv_hotadd_state *ha_region = NULL;
+
+        if (pfn_cnt == 0)
+                return 0;
+
+        if (!dm_device.host_specified_ha_region)
+                if (pfn_covered(pg_start, pfn_cnt))
+                        goto do_pg_range;
+
+        /*
+         * If the host has specified a hot-add range; deal with it first.
+         */
+
+        if ((rg_size != 0) && (!dm_device.host_specified_ha_region)) {
+                ha_region = kzalloc(sizeof(struct hv_hotadd_state), GFP_KERNEL);
+                if (!ha_region)
+                        return 0;
+
+                INIT_LIST_HEAD(&ha_region->list);
+
+                list_add_tail(&ha_region->list, &dm_device.ha_region_list);
+                ha_region->start_pfn = rg_start;
+                ha_region->ha_end_pfn = rg_start;
+                ha_region->covered_start_pfn = pg_start;
+                ha_region->covered_end_pfn = pg_start;
+                ha_region->end_pfn = rg_start + rg_size;
+        }
+
+do_pg_range:
+        /*
+         * Process the page range specified; bringing them
+         * online if possible.
+         */
+        return handle_pg_range(pg_start, pfn_cnt);
+}
+
+#endif
+
+static void hot_add_req(struct work_struct *dummy)
+{
+        struct dm_hot_add_response resp;
+#ifdef CONFIG_MEMORY_HOTPLUG
+        unsigned long pg_start, pfn_cnt;
+        unsigned long rg_start, rg_sz;
+#endif
+        struct hv_dynmem_device *dm = &dm_device;
+
         memset(&resp, 0, sizeof(struct dm_hot_add_response));
         resp.hdr.type = DM_MEM_HOT_ADD_RESPONSE;
         resp.hdr.size = sizeof(struct dm_hot_add_response);
         resp.hdr.trans_id = atomic_inc_return(&trans_id);
 
-        resp.page_count = 0;
-        resp.result = 0;
+#ifdef CONFIG_MEMORY_HOTPLUG
+        pg_start = dm->ha_wrk.ha_page_range.finfo.start_page;
+        pfn_cnt = dm->ha_wrk.ha_page_range.finfo.page_cnt;
 
-        dm_device.state = DM_INITIALIZED;
-        vmbus_sendpacket(dm_device.dev->channel, &resp,
+        rg_start = dm->ha_wrk.ha_region_range.finfo.start_page;
+        rg_sz = dm->ha_wrk.ha_region_range.finfo.page_cnt;
+
+        if ((rg_start == 0) && (!dm->host_specified_ha_region)) {
+                unsigned long region_size;
+                unsigned long region_start;
+
+                /*
+                 * The host has not specified the hot-add region.
+                 * Based on the hot-add page range being specified,
+                 * compute a hot-add region that can cover the pages
+                 * that need to be hot-added while ensuring the alignment
+                 * and size requirements of Linux as it relates to hot-add.
+                 */
+                region_start = pg_start;
+                region_size = (pfn_cnt / HA_CHUNK) * HA_CHUNK;
+                if (pfn_cnt % HA_CHUNK)
+                        region_size += HA_CHUNK;
+
+                region_start = (pg_start / HA_CHUNK) * HA_CHUNK;
+
+                rg_start = region_start;
+                rg_sz = region_size;
+        }
+
+        resp.page_count = process_hot_add(pg_start, pfn_cnt,
+                                        rg_start, rg_sz);
+#endif
+        if (resp.page_count > 0)
+                resp.result = 1;
+        else
+                resp.result = 0;
+
+        if (!do_hot_add || (resp.page_count == 0))
+                pr_info("Memory hot add failed\n");
+
+        dm->state = DM_INITIALIZED;
+        vmbus_sendpacket(dm->dev->channel, &resp,
                         sizeof(struct dm_hot_add_response),
                         (unsigned long)NULL,
                         VM_PKT_DATA_INBAND, 0);
-
 }
 
 static void process_info(struct hv_dynmem_device *dm, struct dm_info_msg *msg)
@@ -867,6 +1200,7 @@ static void balloon_onchannelcallback(void *context)
         struct dm_balloon *bal_msg;
         struct dm_hot_add *ha_msg;
         union dm_mem_page_range *ha_pg_range;
+        union dm_mem_page_range *ha_region;
 
         memset(recv_buffer, 0, sizeof(recv_buffer));
         vmbus_recvpacket(dev->channel, recv_buffer,
@@ -907,8 +1241,26 @@ static void balloon_onchannelcallback(void *context)
                                 pr_warn("Currently hot-adding\n");
                         dm->state = DM_HOT_ADD;
                         ha_msg = (struct dm_hot_add *)recv_buffer;
-                        ha_pg_range = &ha_msg->range;
-                        dm_device.ha_wrk.ha_page_range = *ha_pg_range;
+                        if (ha_msg->hdr.size == sizeof(struct dm_hot_add)) {
+                                /*
+                                 * This is a normal hot-add request specifying
+                                 * hot-add memory.
+                                 */
+                                ha_pg_range = &ha_msg->range;
+                                dm->ha_wrk.ha_page_range = *ha_pg_range;
+                                dm->ha_wrk.ha_region_range.page_range = 0;
+                        } else {
+                                /*
+                                 * Host is specifying that we first hot-add
+                                 * a region and then partially populate this
+                                 * region.
+                                 */
+                                dm->host_specified_ha_region = true;
+                                ha_pg_range = &ha_msg->range;
+                                ha_region = &ha_pg_range[1];
+                                dm->ha_wrk.ha_page_range = *ha_pg_range;
+                                dm->ha_wrk.ha_region_range = *ha_region;
+                        }
                         schedule_work(&dm_device.ha_wrk.wrk);
                         break;
 
@@ -952,8 +1304,10 @@ static int balloon_probe(struct hv_device *dev,
         dm_device.next_version = DYNMEM_PROTOCOL_VERSION_WIN7;
         init_completion(&dm_device.host_event);
         init_completion(&dm_device.config_event);
+        INIT_LIST_HEAD(&dm_device.ha_region_list);
         INIT_WORK(&dm_device.balloon_wrk.wrk, balloon_up);
         INIT_WORK(&dm_device.ha_wrk.wrk, hot_add_req);
+        dm_device.host_specified_ha_region = false;
 
         dm_device.thread =
                  kthread_run(dm_thread_func, &dm_device, "hv_balloon");
@@ -962,6 +1316,10 @@ static int balloon_probe(struct hv_device *dev,
                 goto probe_error1;
         }
 
+#ifdef CONFIG_MEMORY_HOTPLUG
+        set_online_page_callback(&hv_online_page);
+#endif
+
         hv_set_drvdata(dev, &dm_device);
         /*
          * Initiate the hand shake with the host and negotiate
@@ -1006,12 +1364,6 @@ static int balloon_probe(struct hv_device *dev,
         cap_msg.hdr.trans_id = atomic_inc_return(&trans_id);
 
         cap_msg.caps.cap_bits.balloon = 1;
-        /*
-         * While we currently don't support hot-add,
-         * we still advertise this capability since the
-         * host requires that guests partcipating in the
-         * dynamic memory protocol support hot add.
-         */
         cap_msg.caps.cap_bits.hot_add = 1;
 
         /*
@@ -1049,6 +1401,9 @@ static int balloon_probe(struct hv_device *dev,
         return 0;
 
 probe_error2:
+#ifdef CONFIG_MEMORY_HOTPLUG
+        restore_online_page_callback(&hv_online_page);
+#endif
         kthread_stop(dm_device.thread);
 
 probe_error1:
@@ -1061,15 +1416,26 @@ probe_error0:
 static int balloon_remove(struct hv_device *dev)
 {
         struct hv_dynmem_device *dm = hv_get_drvdata(dev);
+        struct list_head *cur, *tmp;
+        struct hv_hotadd_state *has;
 
         if (dm->num_pages_ballooned != 0)
                 pr_warn("Ballooned pages: %d\n", dm->num_pages_ballooned);
 
         cancel_work_sync(&dm->balloon_wrk.wrk);
         cancel_work_sync(&dm->ha_wrk.wrk);
+
         vmbus_close(dev->channel);
         kthread_stop(dm->thread);
         kfree(send_buffer);
+#ifdef CONFIG_MEMORY_HOTPLUG
+        restore_online_page_callback(&hv_online_page);
+#endif
+        list_for_each_safe(cur, tmp, &dm->ha_region_list) {
+                has = list_entry(cur, struct hv_hotadd_state, list);
+                list_del(&has->list);
+                kfree(has);
+        }
 
         return 0;
 }