Merge branch 'x86-uv-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86/uv changes from Ingo Molnar:
 "UV2 BAU productization fixes.

  The BAU (Broadcast Assist Unit) is SGI's fancy out of line way on UV
  hardware to do TLB flushes, instead of the normal APIC IPI methods.
  The commits here fix / work around hangs in their latest hardware
  iteration (UV2).

  My understanding is that the main purpose of the out of line
  signalling channel is to improve scalability: the UV APIC hardware
  glue does not handle broadcasting to many CPUs very well, and this
  matters most for TLB shootdowns.

  [ I don't agree with all aspects of the current approach: in hindsight
    it would have been better to link the BAU at the IPI/APIC driver
    level instead of the TLB shootdown level, where TLB flushes are
    really just one of the uses of broadcast SMP messages.  Doing that
    would improve scalability in some other ways and it would also
    remove a few uglies from the TLB path.  It would also be nice to
    push more is_uv_system() tests into proper x86_init or x86_platform
    callbacks.  Cliff? ]"

* 'x86-uv-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/uv: Work around UV2 BAU hangs
  x86/uv: Implement UV BAU runtime enable and disable control via /proc/sgi_uv/
  x86/uv: Fix the UV BAU destination timeout period

2 files changed, 257 insertions, 224 deletions

diff --git a/arch/x86/include/asm/uv/uv_bau.h b/arch/x86/include/asm/uv/uv_bau.h
index 6149b476d9df..a06983cdc125 100644
--- a/arch/x86/include/asm/uv/uv_bau.h
+++ b/arch/x86/include/asm/uv/uv_bau.h
@@ -140,6 +140,9 @@
 #define IPI_RESET_LIMIT			1
 /* after this # consecutive successes, bump up the throttle if it was lowered */
 #define COMPLETE_THRESHOLD		5
+/* after this # of giveups (fall back to kernel IPI's) disable the use of
+   the BAU for a period of time */
+#define GIVEUP_LIMIT			100
 
 #define UV_LB_SUBNODEID			0x10
 
@@ -166,7 +169,6 @@
 #define FLUSH_RETRY_TIMEOUT		2
 #define FLUSH_GIVEUP			3
 #define FLUSH_COMPLETE			4
-#define FLUSH_RETRY_BUSYBUG		5
 
 /*
  * tuning the action when the numalink network is extremely delayed
@@ -175,7 +177,7 @@
 						   microseconds */
 #define CONGESTED_REPS			10	/* long delays averaged over
 						   this many broadcasts */
-#define CONGESTED_PERIOD		30	/* time for the bau to be
+#define DISABLED_PERIOD			10	/* time for the bau to be
 						   disabled, in seconds */
 /* see msg_type: */
 #define MSG_NOOP			0
@@ -520,6 +522,12 @@ struct ptc_stats {
 	unsigned long	s_uv2_wars;		/* uv2 workaround, perm. busy */
 	unsigned long	s_uv2_wars_hw;		/* uv2 workaround, hiwater */
 	unsigned long	s_uv2_war_waits;	/* uv2 workaround, long waits */
+	unsigned long	s_overipilimit;		/* over the ipi reset limit */
+	unsigned long	s_giveuplimit;		/* disables, over giveup limit*/
+	unsigned long	s_enters;		/* entries to the driver */
+	unsigned long	s_ipifordisabled;	/* fall back to IPI; disabled */
+	unsigned long	s_plugged;		/* plugged by h/w bug*/
+	unsigned long	s_congested;		/* giveup on long wait */
 	/* destination statistics */
 	unsigned long	d_alltlb;		/* times all tlb's on this
 						   cpu were flushed */
@@ -586,8 +594,8 @@ struct bau_control {
 	int			timeout_tries;
 	int			ipi_attempts;
 	int			conseccompletes;
-	int			baudisabled;
-	int			set_bau_off;
+	short			nobau;
+	short			baudisabled;
 	short			cpu;
 	short			osnode;
 	short			uvhub_cpu;
@@ -596,14 +604,16 @@ struct bau_control {
 	short			cpus_in_socket;
 	short			cpus_in_uvhub;
 	short			partition_base_pnode;
-	short			using_desc; /* an index, like uvhub_cpu */
-	unsigned int		inuse_map;
+	short			busy;       /* all were busy (war) */
 	unsigned short		message_number;
 	unsigned short		uvhub_quiesce;
 	short			socket_acknowledge_count[DEST_Q_SIZE];
 	cycles_t		send_message;
+	cycles_t		period_end;
+	cycles_t		period_time;
 	spinlock_t		uvhub_lock;
 	spinlock_t		queue_lock;
+	spinlock_t		disable_lock;
 	/* tunables */
 	int			max_concurr;
 	int			max_concurr_const;
@@ -614,9 +624,9 @@ struct bau_control {
 	int			complete_threshold;
 	int			cong_response_us;
 	int			cong_reps;
-	int			cong_period;
-	unsigned long		clocks_per_100_usec;
-	cycles_t		period_time;
+	cycles_t		disabled_period;
+	int			period_giveups;
+	int			giveup_limit;
 	long			period_requests;
 	struct hub_and_pnode	*thp;
 };
diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c
index 59880afa851f..71b5d5a07d7b 100644
--- a/arch/x86/platform/uv/tlb_uv.c
+++ b/arch/x86/platform/uv/tlb_uv.c
@@ -1,7 +1,7 @@
 /*
  *	SGI UltraViolet TLB flush routines.
  *
- *	(c) 2008-2011 Cliff Wickman <cpw@sgi.com>, SGI.
+ *	(c) 2008-2012 Cliff Wickman <cpw@sgi.com>, SGI.
  *
  *	This code is released under the GNU General Public License version 2 or
  *	later.
@@ -38,8 +38,7 @@ static int timeout_base_ns[] = {
 
 static int timeout_us;
 static int nobau;
-static int baudisabled;
-static spinlock_t disable_lock;
+static int nobau_perm;
 static cycles_t congested_cycles;
 
 /* tunables: */
@@ -47,12 +46,13 @@ static int max_concurr		= MAX_BAU_CONCURRENT;
 static int max_concurr_const	= MAX_BAU_CONCURRENT;
 static int plugged_delay	= PLUGGED_DELAY;
 static int plugsb4reset		= PLUGSB4RESET;
+static int giveup_limit		= GIVEUP_LIMIT;
 static int timeoutsb4reset	= TIMEOUTSB4RESET;
 static int ipi_reset_limit	= IPI_RESET_LIMIT;
 static int complete_threshold	= COMPLETE_THRESHOLD;
 static int congested_respns_us	= CONGESTED_RESPONSE_US;
 static int congested_reps	= CONGESTED_REPS;
-static int congested_period	= CONGESTED_PERIOD;
+static int disabled_period	= DISABLED_PERIOD;
 
 static struct tunables tunables[] = {
 	{&max_concurr, MAX_BAU_CONCURRENT}, /* must be [0] */
@@ -63,7 +63,8 @@ static struct tunables tunables[] = {
 	{&complete_threshold, COMPLETE_THRESHOLD},
 	{&congested_respns_us, CONGESTED_RESPONSE_US},
 	{&congested_reps, CONGESTED_REPS},
-	{&congested_period, CONGESTED_PERIOD}
+	{&disabled_period, DISABLED_PERIOD},
+	{&giveup_limit, GIVEUP_LIMIT}
 };
 
 static struct dentry *tunables_dir;
@@ -120,6 +121,40 @@ static DEFINE_PER_CPU(struct ptc_stats, ptcstats);
 static DEFINE_PER_CPU(struct bau_control, bau_control);
 static DEFINE_PER_CPU(cpumask_var_t, uv_flush_tlb_mask);
 
+static void
+set_bau_on(void)
+{
+	int cpu;
+	struct bau_control *bcp;
+
+	if (nobau_perm) {
+		pr_info("BAU not initialized; cannot be turned on\n");
+		return;
+	}
+	nobau = 0;
+	for_each_present_cpu(cpu) {
+		bcp = &per_cpu(bau_control, cpu);
+		bcp->nobau = 0;
+	}
+	pr_info("BAU turned on\n");
+	return;
+}
+
+static void
+set_bau_off(void)
+{
+	int cpu;
+	struct bau_control *bcp;
+
+	nobau = 1;
+	for_each_present_cpu(cpu) {
+		bcp = &per_cpu(bau_control, cpu);
+		bcp->nobau = 1;
+	}
+	pr_info("BAU turned off\n");
+	return;
+}
+
 /*
  * Determine the first node on a uvhub. 'Nodes' are used for kernel
  * memory allocation.
@@ -278,7 +313,7 @@ static void bau_process_message(struct msg_desc *mdp, struct bau_control *bcp,
 		 * Both sockets dump their completed count total into
 		 * the message's count.
 		 */
-		smaster->socket_acknowledge_count[mdp->msg_slot] = 0;
+		*sp = 0;
 		asp = (struct atomic_short *)&msg->acknowledge_count;
 		msg_ack_count = atom_asr(socket_ack_count, asp);
 
@@ -491,16 +526,15 @@ static int uv1_wait_completion(struct bau_desc *bau_desc,
 }
 
 /*
- * UV2 has an extra bit of status in the ACTIVATION_STATUS_2 register.
+ * UV2 could have an extra bit of status in the ACTIVATION_STATUS_2 register.
+ * But not currently used.
  */
 static unsigned long uv2_read_status(unsigned long offset, int rshft, int desc)
 {
 	unsigned long descriptor_status;
-	unsigned long descriptor_status2;
 
-	descriptor_status = ((read_lmmr(offset) >> rshft) & UV_ACT_STATUS_MASK);
-	descriptor_status2 = (read_mmr_uv2_status() >> desc) & 0x1UL;
-	descriptor_status = (descriptor_status << 1) | descriptor_status2;
+	descriptor_status =
+		((read_lmmr(offset) >> rshft) & UV_ACT_STATUS_MASK) << 1;
 	return descriptor_status;
 }
 
@@ -531,87 +565,11 @@ int normal_busy(struct bau_control *bcp)
  */
 int handle_uv2_busy(struct bau_control *bcp)
 {
-	int busy_one = bcp->using_desc;
-	int normal = bcp->uvhub_cpu;
-	int selected = -1;
-	int i;
-	unsigned long descriptor_status;
-	unsigned long status;
-	int mmr_offset;
-	struct bau_desc *bau_desc_old;
-	struct bau_desc *bau_desc_new;
-	struct bau_control *hmaster = bcp->uvhub_master;
 	struct ptc_stats *stat = bcp->statp;
-	cycles_t ttm;
 
 	stat->s_uv2_wars++;
-	spin_lock(&hmaster->uvhub_lock);
-	/* try for the original first */
-	if (busy_one != normal) {
-		if (!normal_busy(bcp))
-			selected = normal;
-	}
-	if (selected < 0) {
-		/* can't use the normal, select an alternate */
-		mmr_offset = UVH_LB_BAU_SB_ACTIVATION_STATUS_1;
-		descriptor_status = read_lmmr(mmr_offset);
-
-		/* scan available descriptors 32-63 */
-		for (i = 0; i < UV_CPUS_PER_AS; i++) {
-			if ((hmaster->inuse_map & (1 << i)) == 0) {
-				status = ((descriptor_status >>
-						(i * UV_ACT_STATUS_SIZE)) &
-						UV_ACT_STATUS_MASK) << 1;
-				if (status != UV2H_DESC_BUSY) {
-					selected = i + UV_CPUS_PER_AS;
-					break;
-				}
-			}
-		}
-	}
-
-	if (busy_one != normal)
-		/* mark the busy alternate as not in-use */
-		hmaster->inuse_map &= ~(1 << (busy_one - UV_CPUS_PER_AS));
-
-	if (selected >= 0) {
-		/* switch to the selected descriptor */
-		if (selected != normal) {
-			/* set the selected alternate as in-use */
-			hmaster->inuse_map |=
-					(1 << (selected - UV_CPUS_PER_AS));
-			if (selected > stat->s_uv2_wars_hw)
-				stat->s_uv2_wars_hw = selected;
-		}
-		bau_desc_old = bcp->descriptor_base;
-		bau_desc_old += (ITEMS_PER_DESC * busy_one);
-		bcp->using_desc = selected;
-		bau_desc_new = bcp->descriptor_base;
-		bau_desc_new += (ITEMS_PER_DESC * selected);
-		*bau_desc_new = *bau_desc_old;
-	} else {
-		/*
-		 * All are busy. Wait for the normal one for this cpu to
-		 * free up.
-		 */
-		stat->s_uv2_war_waits++;
-		spin_unlock(&hmaster->uvhub_lock);
-		ttm = get_cycles();
-		do {
-			cpu_relax();
-		} while (normal_busy(bcp));
-		spin_lock(&hmaster->uvhub_lock);
-		/* switch to the original descriptor */
-		bcp->using_desc = normal;
-		bau_desc_old = bcp->descriptor_base;
-		bau_desc_old += (ITEMS_PER_DESC * bcp->using_desc);
-		bcp->using_desc = (ITEMS_PER_DESC * normal);
-		bau_desc_new = bcp->descriptor_base;
-		bau_desc_new += (ITEMS_PER_DESC * normal);
-		*bau_desc_new = *bau_desc_old; /* copy the entire descriptor */
-	}
-	spin_unlock(&hmaster->uvhub_lock);
-	return FLUSH_RETRY_BUSYBUG;
+	bcp->busy = 1;
+	return FLUSH_GIVEUP;
 }
 
 static int uv2_wait_completion(struct bau_desc *bau_desc,
@@ -620,7 +578,7 @@ static int uv2_wait_completion(struct bau_desc *bau_desc,
 {
 	unsigned long descriptor_stat;
 	cycles_t ttm;
-	int desc = bcp->using_desc;
+	int desc = bcp->uvhub_cpu;
 	long busy_reps = 0;
 	struct ptc_stats *stat = bcp->statp;
 
@@ -628,24 +586,38 @@ static int uv2_wait_completion(struct bau_desc *bau_desc,
 
 	/* spin on the status MMR, waiting for it to go idle */
 	while (descriptor_stat != UV2H_DESC_IDLE) {
-		/*
-		 * Our software ack messages may be blocked because
-		 * there are no swack resources available.  As long
-		 * as none of them has timed out hardware will NACK
-		 * our message and its state will stay IDLE.
-		 */
-		if ((descriptor_stat == UV2H_DESC_SOURCE_TIMEOUT) ||
-		    (descriptor_stat == UV2H_DESC_DEST_PUT_ERR)) {
+		if ((descriptor_stat == UV2H_DESC_SOURCE_TIMEOUT)) {
+			/*
+			 * A h/w bug on the destination side may
+			 * have prevented the message being marked
+			 * pending, thus it doesn't get replied to
+			 * and gets continually nacked until it times
+			 * out with a SOURCE_TIMEOUT.
+			 */
 			stat->s_stimeout++;
 			return FLUSH_GIVEUP;
-		} else if (descriptor_stat == UV2H_DESC_DEST_STRONG_NACK) {
-			stat->s_strongnacks++;
-			bcp->conseccompletes = 0;
-			return FLUSH_GIVEUP;
 		} else if (descriptor_stat == UV2H_DESC_DEST_TIMEOUT) {
+			ttm = get_cycles();
+
+			/*
+			 * Our retries may be blocked by all destination
+			 * swack resources being consumed, and a timeout
+			 * pending.  In that case hardware returns the
+			 * ERROR that looks like a destination timeout.
+			 * Without using the extended status we have to
+			 * deduce from the short time that this was a
+			 * strong nack.
+			 */
+			if (cycles_2_us(ttm - bcp->send_message) < timeout_us) {
+				bcp->conseccompletes = 0;
+				stat->s_plugged++;
+				/* FLUSH_RETRY_PLUGGED causes hang on boot */
+				return FLUSH_GIVEUP;
+			}
 			stat->s_dtimeout++;
 			bcp->conseccompletes = 0;
-			return FLUSH_RETRY_TIMEOUT;
+			/* FLUSH_RETRY_TIMEOUT causes hang on boot */
+			return FLUSH_GIVEUP;
 		} else {
 			busy_reps++;
 			if (busy_reps > 1000000) {
@@ -653,9 +625,8 @@ static int uv2_wait_completion(struct bau_desc *bau_desc,
 				busy_reps = 0;
 				ttm = get_cycles();
 				if ((ttm - bcp->send_message) >
-					(bcp->clocks_per_100_usec)) {
+						bcp->timeout_interval)
 					return handle_uv2_busy(bcp);
-				}
 			}
 			/*
 			 * descriptor_stat is still BUSY
@@ -679,7 +650,7 @@ static int wait_completion(struct bau_desc *bau_desc,
 {
 	int right_shift;
 	unsigned long mmr_offset;
-	int desc = bcp->using_desc;
+	int desc = bcp->uvhub_cpu;
 
 	if (desc < UV_CPUS_PER_AS) {
 		mmr_offset = UVH_LB_BAU_SB_ACTIVATION_STATUS_0;
@@ -758,33 +729,31 @@ static void destination_timeout(struct bau_desc *bau_desc,
 }
 
 /*
- * Completions are taking a very long time due to a congested numalink
- * network.
+ * Stop all cpus on a uvhub from using the BAU for a period of time.
+ * This is reversed by check_enable.
  */
-static void disable_for_congestion(struct bau_control *bcp,
-					struct ptc_stats *stat)
+static void disable_for_period(struct bau_control *bcp, struct ptc_stats *stat)
 {
-	/* let only one cpu do this disabling */
-	spin_lock(&disable_lock);
-
-	if (!baudisabled && bcp->period_requests &&
-	    ((bcp->period_time / bcp->period_requests) > congested_cycles)) {
-		int tcpu;
-		struct bau_control *tbcp;
-		/* it becomes this cpu's job to turn on the use of the
-		   BAU again */
-		baudisabled = 1;
-		bcp->set_bau_off = 1;
-		bcp->set_bau_on_time = get_cycles();
-		bcp->set_bau_on_time += sec_2_cycles(bcp->cong_period);
+	int tcpu;
+	struct bau_control *tbcp;
+	struct bau_control *hmaster;
+	cycles_t tm1;
+
+	hmaster = bcp->uvhub_master;
+	spin_lock(&hmaster->disable_lock);
+	if (!bcp->baudisabled) {
 		stat->s_bau_disabled++;
+		tm1 = get_cycles();
 		for_each_present_cpu(tcpu) {
 			tbcp = &per_cpu(bau_control, tcpu);
-			tbcp->baudisabled = 1;
+			if (tbcp->uvhub_master == hmaster) {
+				tbcp->baudisabled = 1;
+				tbcp->set_bau_on_time =
+					tm1 + bcp->disabled_period;
+			}
 		}
 	}
-
-	spin_unlock(&disable_lock);
+	spin_unlock(&hmaster->disable_lock);
 }
 
 static void count_max_concurr(int stat, struct bau_control *bcp,
@@ -815,16 +784,30 @@ static void record_send_stats(cycles_t time1, cycles_t time2,
 			bcp->period_requests++;
 			bcp->period_time += elapsed;
 			if ((elapsed > congested_cycles) &&
-			    (bcp->period_requests > bcp->cong_reps))
-				disable_for_congestion(bcp, stat);
+			    (bcp->period_requests > bcp->cong_reps) &&
+			    ((bcp->period_time / bcp->period_requests) >
+							congested_cycles)) {
+				stat->s_congested++;
+				disable_for_period(bcp, stat);
+			}
 		}
 	} else
 		stat->s_requestor--;
 
 	if (completion_status == FLUSH_COMPLETE && try > 1)
 		stat->s_retriesok++;
-	else if (completion_status == FLUSH_GIVEUP)
+	else if (completion_status == FLUSH_GIVEUP) {
 		stat->s_giveup++;
+		if (get_cycles() > bcp->period_end)
+			bcp->period_giveups = 0;
+		bcp->period_giveups++;
+		if (bcp->period_giveups == 1)
+			bcp->period_end = get_cycles() + bcp->disabled_period;
+		if (bcp->period_giveups > bcp->giveup_limit) {
+			disable_for_period(bcp, stat);
+			stat->s_giveuplimit++;
+		}
+	}
 }
 
 /*
@@ -868,7 +851,8 @@ static void handle_cmplt(int completion_status, struct bau_desc *bau_desc,
  * Returns 1 if it gives up entirely and the original cpu mask is to be
  * returned to the kernel.
  */
-int uv_flush_send_and_wait(struct cpumask *flush_mask, struct bau_control *bcp)
+int uv_flush_send_and_wait(struct cpumask *flush_mask, struct bau_control *bcp,
+	struct bau_desc *bau_desc)
 {
 	int seq_number = 0;
 	int completion_stat = 0;
@@ -881,24 +865,23 @@ int uv_flush_send_and_wait(struct cpumask *flush_mask, struct bau_control *bcp)
 	struct bau_control *hmaster = bcp->uvhub_master;
 	struct uv1_bau_msg_header *uv1_hdr = NULL;
 	struct uv2_bau_msg_header *uv2_hdr = NULL;
-	struct bau_desc *bau_desc;
 
-	if (bcp->uvhub_version == 1)
+	if (bcp->uvhub_version == 1) {
+		uv1 = 1;
 		uv1_throttle(hmaster, stat);
+	}
 
 	while (hmaster->uvhub_quiesce)
 		cpu_relax();
 
 	time1 = get_cycles();
+	if (uv1)
+		uv1_hdr = &bau_desc->header.uv1_hdr;
+	else
+		uv2_hdr = &bau_desc->header.uv2_hdr;
+
 	do {
-		bau_desc = bcp->descriptor_base;
-		bau_desc += (ITEMS_PER_DESC * bcp->using_desc);
-		if (bcp->uvhub_version == 1) {
-			uv1 = 1;
-			uv1_hdr = &bau_desc->header.uv1_hdr;
-		} else
-			uv2_hdr = &bau_desc->header.uv2_hdr;
-		if ((try == 0) || (completion_stat == FLUSH_RETRY_BUSYBUG)) {
+		if (try == 0) {
 			if (uv1)
 				uv1_hdr->msg_type = MSG_REGULAR;
 			else
@@ -916,25 +899,24 @@ int uv_flush_send_and_wait(struct cpumask *flush_mask, struct bau_control *bcp)
 			uv1_hdr->sequence = seq_number;
 		else
 			uv2_hdr->sequence = seq_number;
-		index = (1UL << AS_PUSH_SHIFT) | bcp->using_desc;
+		index = (1UL << AS_PUSH_SHIFT) | bcp->uvhub_cpu;
 		bcp->send_message = get_cycles();
 
 		write_mmr_activation(index);
 
 		try++;
 		completion_stat = wait_completion(bau_desc, bcp, try);
-		/* UV2: wait_completion() may change the bcp->using_desc */
 
 		handle_cmplt(completion_stat, bau_desc, bcp, hmaster, stat);
 
 		if (bcp->ipi_attempts >= bcp->ipi_reset_limit) {
 			bcp->ipi_attempts = 0;
+			stat->s_overipilimit++;
 			completion_stat = FLUSH_GIVEUP;
 			break;
 		}
 		cpu_relax();
 	} while ((completion_stat == FLUSH_RETRY_PLUGGED) ||
-		 (completion_stat == FLUSH_RETRY_BUSYBUG) ||
 		 (completion_stat == FLUSH_RETRY_TIMEOUT));
 
 	time2 = get_cycles();
@@ -955,28 +937,33 @@ int uv_flush_send_and_wait(struct cpumask *flush_mask, struct bau_control *bcp)
 }
 
 /*
- * The BAU is disabled. When the disabled time period has expired, the cpu
- * that disabled it must re-enable it.
- * Return 0 if it is re-enabled for all cpus.
+ * The BAU is disabled for this uvhub. When the disabled time period has
+ * expired re-enable it.
+ * Return 0 if it is re-enabled for all cpus on this uvhub.
  */
 static int check_enable(struct bau_control *bcp, struct ptc_stats *stat)
 {
 	int tcpu;
 	struct bau_control *tbcp;
+	struct bau_control *hmaster;
 
-	if (bcp->set_bau_off) {
-		if (get_cycles() >= bcp->set_bau_on_time) {
-			stat->s_bau_reenabled++;
-			baudisabled = 0;
-			for_each_present_cpu(tcpu) {
-				tbcp = &per_cpu(bau_control, tcpu);
+	hmaster = bcp->uvhub_master;
+	spin_lock(&hmaster->disable_lock);
+	if (bcp->baudisabled && (get_cycles() >= bcp->set_bau_on_time)) {
+		stat->s_bau_reenabled++;
+		for_each_present_cpu(tcpu) {
+			tbcp = &per_cpu(bau_control, tcpu);
+			if (tbcp->uvhub_master == hmaster) {
 				tbcp->baudisabled = 0;
 				tbcp->period_requests = 0;
 				tbcp->period_time = 0;
+				tbcp->period_giveups = 0;
 			}
-			return 0;
 		}
+		spin_unlock(&hmaster->disable_lock);
+		return 0;
 	}
+	spin_unlock(&hmaster->disable_lock);
 	return -1;
 }
 
@@ -1078,18 +1065,32 @@ const struct cpumask *uv_flush_tlb_others(const struct cpumask *cpumask,
 	struct cpumask *flush_mask;
 	struct ptc_stats *stat;
 	struct bau_control *bcp;
-
-	/* kernel was booted 'nobau' */
-	if (nobau)
-		return cpumask;
+	unsigned long descriptor_status;
+	unsigned long status;
 
 	bcp = &per_cpu(bau_control, cpu);
 	stat = bcp->statp;
+	stat->s_enters++;
+
+	if (bcp->nobau)
+		return cpumask;
+
+	if (bcp->busy) {
+		descriptor_status =
+			read_lmmr(UVH_LB_BAU_SB_ACTIVATION_STATUS_0);
+		status = ((descriptor_status >> (bcp->uvhub_cpu *
+			UV_ACT_STATUS_SIZE)) & UV_ACT_STATUS_MASK) << 1;
+		if (status == UV2H_DESC_BUSY)
+			return cpumask;
+		bcp->busy = 0;
+	}
 
 	/* bau was disabled due to slow response */
 	if (bcp->baudisabled) {
-		if (check_enable(bcp, stat))
+		if (check_enable(bcp, stat)) {
+			stat->s_ipifordisabled++;
 			return cpumask;
+		}
 	}
 
 	/*
@@ -1105,7 +1106,7 @@ const struct cpumask *uv_flush_tlb_others(const struct cpumask *cpumask,
 		stat->s_ntargself++;
 
 	bau_desc = bcp->descriptor_base;
-	bau_desc += (ITEMS_PER_DESC * bcp->using_desc);
+	bau_desc += (ITEMS_PER_DESC * bcp->uvhub_cpu);
 	bau_uvhubs_clear(&bau_desc->distribution, UV_DISTRIBUTION_SIZE);
 	if (set_distrib_bits(flush_mask, bcp, bau_desc, &locals, &remotes))
 		return NULL;
@@ -1118,25 +1119,27 @@ const struct cpumask *uv_flush_tlb_others(const struct cpumask *cpumask,
 	 * uv_flush_send_and_wait returns 0 if all cpu's were messaged,
 	 * or 1 if it gave up and the original cpumask should be returned.
 	 */
-	if (!uv_flush_send_and_wait(flush_mask, bcp))
+	if (!uv_flush_send_and_wait(flush_mask, bcp, bau_desc))
 		return NULL;
 	else
 		return cpumask;
 }
 
 /*
- * Search the message queue for any 'other' message with the same software
- * acknowledge resource bit vector.
+ * Search the message queue for any 'other' unprocessed message with the
+ * same software acknowledge resource bit vector as the 'msg' message.
  */
 struct bau_pq_entry *find_another_by_swack(struct bau_pq_entry *msg,
-			struct bau_control *bcp, unsigned char swack_vec)
+					   struct bau_control *bcp)
 {
 	struct bau_pq_entry *msg_next = msg + 1;
+	unsigned char swack_vec = msg->swack_vec;
 
 	if (msg_next > bcp->queue_last)
 		msg_next = bcp->queue_first;
-	while ((msg_next->swack_vec != 0) && (msg_next != msg)) {
-		if (msg_next->swack_vec == swack_vec)
+	while (msg_next != msg) {
+		if ((msg_next->canceled == 0) && (msg_next->replied_to == 0) &&
+				(msg_next->swack_vec == swack_vec))
 			return msg_next;
 		msg_next++;
 		if (msg_next > bcp->queue_last)
@@ -1165,32 +1168,30 @@ void process_uv2_message(struct msg_desc *mdp, struct bau_control *bcp)
 		 * This message was assigned a swack resource, but no
 		 * reserved acknowlegment is pending.
 		 * The bug has prevented this message from setting the MMR.
-		 * And no other message has used the same sw_ack resource.
-		 * Do the requested shootdown but do not reply to the msg.
-		 * (the 0 means make no acknowledge)
 		 */
-		bau_process_message(mdp, bcp, 0);
-		return;
-	}
-
-	/*
-	 * Some message has set the MMR 'pending' bit; it might have been
-	 * another message.  Look for that message.
-	 */
-	other_msg = find_another_by_swack(msg, bcp, msg->swack_vec);
-	if (other_msg) {
-		/* There is another.  Do not ack the current one. */
-		bau_process_message(mdp, bcp, 0);
 		/*
-		 * Let the natural processing of that message acknowledge
-		 * it. Don't get the processing of sw_ack's out of order.
+		 * Some message has set the MMR 'pending' bit; it might have
+		 * been another message.  Look for that message.
 		 */
-		return;
+		other_msg = find_another_by_swack(msg, bcp);
+		if (other_msg) {
+			/*
+			 * There is another. Process this one but do not
+			 * ack it.
+			 */
+			bau_process_message(mdp, bcp, 0);
+			/*
+			 * Let the natural processing of that other message
+			 * acknowledge it. Don't get the processing of sw_ack's
+			 * out of order.
+			 */
+			return;
+		}
 	}
 
 	/*
-	 * There is no other message using this sw_ack, so it is safe to
-	 * acknowledge it.
+	 * Either the MMR shows this one pending a reply or there is no
+	 * other message using this sw_ack, so it is safe to acknowledge it.
 	 */
 	bau_process_message(mdp, bcp, 1);
 
@@ -1295,7 +1296,8 @@ static void __init enable_timeouts(void)
 		 */
 		mmr_image |= (1L << SOFTACK_MSHIFT);
 		if (is_uv2_hub()) {
-			mmr_image |= (1L << UV2_EXT_SHFT);
+			/* hw bug workaround; do not use extended status */
+			mmr_image &= ~(1L << UV2_EXT_SHFT);
 		}
 		write_mmr_misc_control(pnode, mmr_image);
 	}
@@ -1338,29 +1340,34 @@ static inline unsigned long long usec_2_cycles(unsigned long microsec)
 static int ptc_seq_show(struct seq_file *file, void *data)
 {
 	struct ptc_stats *stat;
+	struct bau_control *bcp;
 	int cpu;
 
 	cpu = *(loff_t *)data;
 	if (!cpu) {
 		seq_printf(file,
-			"# cpu sent stime self locals remotes ncpus localhub ");
+		 "# cpu bauoff sent stime self locals remotes ncpus localhub ");
 		seq_printf(file,
 			"remotehub numuvhubs numuvhubs16 numuvhubs8 ");
 		seq_printf(file,
-		    "numuvhubs4 numuvhubs2 numuvhubs1 dto snacks retries rok ");
+			"numuvhubs4 numuvhubs2 numuvhubs1 dto snacks retries ");
+		seq_printf(file,
+			"rok resetp resett giveup sto bz throt disable ");
 		seq_printf(file,
-			"resetp resett giveup sto bz throt swack recv rtime ");
+			"enable wars warshw warwaits enters ipidis plugged ");
 		seq_printf(file,
-			"all one mult none retry canc nocan reset rcan ");
+			"ipiover glim cong swack recv rtime all one mult ");
 		seq_printf(file,
-			"disable enable wars warshw warwaits\n");
+			"none retry canc nocan reset rcan\n");
 	}
 	if (cpu < num_possible_cpus() && cpu_online(cpu)) {
-		stat = &per_cpu(ptcstats, cpu);
+		bcp = &per_cpu(bau_control, cpu);
+		stat = bcp->statp;
 		/* source side statistics */
 		seq_printf(file,
-			"cpu %d %ld %ld %ld %ld %ld %ld %ld %ld %ld %ld ",
-			   cpu, stat->s_requestor, cycles_2_us(stat->s_time),
+			"cpu %d %d %ld %ld %ld %ld %ld %ld %ld %ld %ld %ld ",
+			   cpu, bcp->nobau, stat->s_requestor,
+			   cycles_2_us(stat->s_time),
 			   stat->s_ntargself, stat->s_ntarglocals,
 			   stat->s_ntargremotes, stat->s_ntargcpu,
 			   stat->s_ntarglocaluvhub, stat->s_ntargremoteuvhub,
@@ -1374,20 +1381,23 @@ static int ptc_seq_show(struct seq_file *file, void *data)
 			   stat->s_resets_plug, stat->s_resets_timeout,
 			   stat->s_giveup, stat->s_stimeout,
 			   stat->s_busy, stat->s_throttles);
+		seq_printf(file, "%ld %ld %ld %ld %ld %ld %ld %ld %ld %ld %ld ",
+			   stat->s_bau_disabled, stat->s_bau_reenabled,
+			   stat->s_uv2_wars, stat->s_uv2_wars_hw,
+			   stat->s_uv2_war_waits, stat->s_enters,
+			   stat->s_ipifordisabled, stat->s_plugged,
+			   stat->s_overipilimit, stat->s_giveuplimit,
+			   stat->s_congested);
 
 		/* destination side statistics */
 		seq_printf(file,
-			   "%lx %ld %ld %ld %ld %ld %ld %ld %ld %ld %ld %ld ",
+			"%lx %ld %ld %ld %ld %ld %ld %ld %ld %ld %ld %ld\n",
 			   read_gmmr_sw_ack(uv_cpu_to_pnode(cpu)),
 			   stat->d_requestee, cycles_2_us(stat->d_time),
 			   stat->d_alltlb, stat->d_onetlb, stat->d_multmsg,
 			   stat->d_nomsg, stat->d_retries, stat->d_canceled,
 			   stat->d_nocanceled, stat->d_resets,
 			   stat->d_rcanceled);
-		seq_printf(file, "%ld %ld %ld %ld %ld\n",
-			stat->s_bau_disabled, stat->s_bau_reenabled,
-			stat->s_uv2_wars, stat->s_uv2_wars_hw,
-			stat->s_uv2_war_waits);
 	}
 	return 0;
 }
@@ -1401,13 +1411,14 @@ static ssize_t tunables_read(struct file *file, char __user *userbuf,
 	char *buf;
 	int ret;
 
-	buf = kasprintf(GFP_KERNEL, "%s %s %s\n%d %d %d %d %d %d %d %d %d\n",
-		"max_concur plugged_delay plugsb4reset",
-		"timeoutsb4reset ipi_reset_limit complete_threshold",
-		"congested_response_us congested_reps congested_period",
+	buf = kasprintf(GFP_KERNEL, "%s %s %s\n%d %d %d %d %d %d %d %d %d %d\n",
+		"max_concur plugged_delay plugsb4reset timeoutsb4reset",
+		"ipi_reset_limit complete_threshold congested_response_us",
+		"congested_reps disabled_period giveup_limit",
 		max_concurr, plugged_delay, plugsb4reset,
 		timeoutsb4reset, ipi_reset_limit, complete_threshold,
-		congested_respns_us, congested_reps, congested_period);
+		congested_respns_us, congested_reps, disabled_period,
+		giveup_limit);
 
 	if (!buf)
 		return -ENOMEM;
@@ -1438,6 +1449,14 @@ static ssize_t ptc_proc_write(struct file *file, const char __user *user,
 		return -EFAULT;
 	optstr[count - 1] = '\0';
 
+	if (!strcmp(optstr, "on")) {
+		set_bau_on();
+		return count;
+	} else if (!strcmp(optstr, "off")) {
+		set_bau_off();
+		return count;
+	}
+
 	if (strict_strtol(optstr, 10, &input_arg) < 0) {
 		printk(KERN_DEBUG "%s is invalid\n", optstr);
 		return -EINVAL;
@@ -1570,7 +1589,8 @@ static ssize_t tunables_write(struct file *file, const char __user *user,
 		bcp->complete_threshold =	complete_threshold;
 		bcp->cong_response_us =		congested_respns_us;
 		bcp->cong_reps =		congested_reps;
-		bcp->cong_period =		congested_period;
+		bcp->disabled_period =		sec_2_cycles(disabled_period);
+		bcp->giveup_limit =		giveup_limit;
 	}
 	return count;
 }
@@ -1699,6 +1719,10 @@ static void activation_descriptor_init(int node, int pnode, int base_pnode)
 			 *   fairness chaining multilevel count replied_to
 			 */
 		} else {
+			/*
+			 * BIOS uses legacy mode, but UV2 hardware always
+			 * uses native mode for selective broadcasts.
+			 */
 			uv2_hdr = &bd2->header.uv2_hdr;
 			uv2_hdr->swack_flag =	1;
 			uv2_hdr->base_dest_nasid =
@@ -1811,8 +1835,8 @@ static int calculate_destination_timeout(void)
 		index = (mmr_image >> BAU_URGENCY_7_SHIFT) & BAU_URGENCY_7_MASK;
 		mmr_image = uv_read_local_mmr(UVH_TRANSACTION_TIMEOUT);
 		mult2 = (mmr_image >> BAU_TRANS_SHIFT) & BAU_TRANS_MASK;
-		base = timeout_base_ns[index];
-		ts_ns = base * mult1 * mult2;
+		ts_ns = timeout_base_ns[index];
+		ts_ns *= (mult1 * mult2);
 		ret = ts_ns / 1000;
 	} else {
 		/* 4 bits  0/1 for 10/80us base, 3 bits of multiplier */
@@ -1836,6 +1860,8 @@ static void __init init_per_cpu_tunables(void)
 	for_each_present_cpu(cpu) {
 		bcp = &per_cpu(bau_control, cpu);
 		bcp->baudisabled		= 0;
+		if (nobau)
+			bcp->nobau		= 1;
 		bcp->statp			= &per_cpu(ptcstats, cpu);
 		/* time interval to catch a hardware stay-busy bug */
 		bcp->timeout_interval		= usec_2_cycles(2*timeout_us);
@@ -1848,10 +1874,11 @@ static void __init init_per_cpu_tunables(void)
 		bcp->complete_threshold		= complete_threshold;
 		bcp->cong_response_us		= congested_respns_us;
 		bcp->cong_reps			= congested_reps;
-		bcp->cong_period		= congested_period;
-		bcp->clocks_per_100_usec =	usec_2_cycles(100);
+		bcp->disabled_period =		sec_2_cycles(disabled_period);
+		bcp->giveup_limit =		giveup_limit;
 		spin_lock_init(&bcp->queue_lock);
 		spin_lock_init(&bcp->uvhub_lock);
+		spin_lock_init(&bcp->disable_lock);
 	}
 }
 
@@ -1972,7 +1999,6 @@ static int scan_sock(struct socket_desc *sdp, struct uvhub_desc *bdp,
 		}
 		bcp->uvhub_master = *hmasterp;
 		bcp->uvhub_cpu = uv_cpu_hub_info(cpu)->blade_processor_id;
-		bcp->using_desc = bcp->uvhub_cpu;
 		if (bcp->uvhub_cpu >= MAX_CPUS_PER_UVHUB) {
 			printk(KERN_EMERG "%d cpus per uvhub invalid\n",
 				bcp->uvhub_cpu);
@@ -2069,16 +2095,12 @@ static int __init uv_bau_init(void)
 	if (!is_uv_system())
 		return 0;
 
-	if (nobau)
-		return 0;
-
 	for_each_possible_cpu(cur_cpu) {
 		mask = &per_cpu(uv_flush_tlb_mask, cur_cpu);
 		zalloc_cpumask_var_node(mask, GFP_KERNEL, cpu_to_node(cur_cpu));
 	}
 
 	nuvhubs = uv_num_possible_blades();
-	spin_lock_init(&disable_lock);
 	congested_cycles = usec_2_cycles(congested_respns_us);
 
 	uv_base_pnode = 0x7fffffff;
@@ -2091,7 +2113,8 @@ static int __init uv_bau_init(void)
 	enable_timeouts();
 
 	if (init_per_cpu(nuvhubs, uv_base_pnode)) {
-		nobau = 1;
+		set_bau_off();
+		nobau_perm = 1;
 		return 0;
 	}