[PATCH RESEND 5/6] Drivers: hv: balloon: Implement hot-add functionality

From: K. Y. Srinivasan
Date: Tue Mar 12 2013 - 13:33:05 EST

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

Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
Reviewed-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
---
drivers/hv/Kconfig | 2 +-
drivers/hv/hv_balloon.c | 393 ++++++++++++++++++++++++++++++++++++++++++++---
2 files changed, 373 insertions(+), 22 deletions(-)

diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 64630f1..5415fac 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -15,7 +15,7 @@ config HYPERV_UTILS

config HYPERV_BALLOON
tristate "Microsoft Hyper-V Balloon driver"
- depends on HYPERV
+ depends on HYPERV && MEMORY_HOTPLUG
help
Select this option to enable Hyper-V Balloon driver.

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 4743db9..2cdf3d7 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 +535,321 @@ struct hv_dynmem_device {

static struct hv_dynmem_device dm_device;

-static void hot_add_req(struct work_struct *dummy)
+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;
+
+ init_completion(&dm_device.ol_waitevent);
+ dm_device.ha_waiting = true;
+
+ 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;
+ }
+
+ /*
+ * 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++;
+ }
+ }
+}

- if (do_hot_add) {
+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;

- pr_info("Memory hot add not supported\n");
+ has->end_pfn += new_inc;
+ }

/*
- * Currently we do not support hot add.
- * Just fail the request.
+ * 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);
+}
+
+static void hot_add_req(struct work_struct *dummy)
+{
+ struct dm_hot_add_response resp;
+ unsigned long pg_start, pfn_cnt;
+ unsigned long rg_start, rg_sz;
+ 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;
+ 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);
+ 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 +1192,7 @@ 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 +1233,26 @@ 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 +1296,10 @@ 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 +1308,8 @@ static int balloon_probe(struct hv_device *dev,
goto probe_error1;
}

+ set_online_page_callback(&hv_online_page);
+
hv_set_drvdata(dev, &dm_device);
/*
* Initiate the hand shake with the host and negotiate
@@ -1006,12 +1354,6 @@ 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;

/*
@@ -1061,15 +1403,24 @@ 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);
+ restore_online_page_callback(&hv_online_page);
+ 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;
}
--
1.7.4.1

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