[PATCH 09/13] xen: implement 3-level event channel routines

[Wei Liu <wei.liu2@citrix.com>]

Only do_upcall, debug_interrupt and unmask_evtchn are required.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
 drivers/xen/events.c |  291 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 291 insertions(+)

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 30ca620..d953e81 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -51,6 +51,9 @@
 #include <xen/interface/hvm/hvm_op.h>
 #include <xen/interface/hvm/params.h>
 
+/* Helper macro(s) */
+#define LONG_BITORDER (BITS_PER_LONG == 64 ? 6 : 5)
+
 /* N-level event channel, starting from 2 */
 unsigned int evtchn_level = 2;
 EXPORT_SYMBOL_GPL(evtchn_level);
@@ -61,6 +64,9 @@ EXPORT_SYMBOL_GPL(nr_event_channels);
 static unsigned long *evtchn_pending;
 static unsigned long *evtchn_mask;
 
+/* 2nd level selector for 3-level event channel */
+static DEFINE_PER_CPU(unsigned long[sizeof(unsigned long) * 8], evtchn_sel_l2);
+
 /*
  * This lock protects updates to the following mapping and reference-count
  * arrays. The lock does not need to be acquired to read the mapping tables.
@@ -396,6 +402,28 @@ static inline void __unmask_local_port_l2(int port)
 		vcpu_info->evtchn_upcall_pending = 1;
 }
 
+static inline void __unmask_local_port_l3(int port)
+{
+	struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
+	int cpu = smp_processor_id();
+	unsigned int l1bit = port >> (LONG_BITORDER << 1);
+	unsigned int l2bit = port >> LONG_BITORDER;
+
+	sync_clear_bit(port, &evtchn_mask[0]);
+
+	/*
+	 * The following is basically the equivalent of
+	 * 'hw_resend_irq'. Just like a real IO-APIC we 'lose
+	 * the interrupt edge' if the channel is masked.
+	 */
+	if (sync_test_bit(port, &evtchn_pending[0]) &&
+	    !sync_test_and_set_bit(l2bit,
+				   &per_cpu(evtchn_sel_l2, cpu)[0]) &&
+	    !sync_test_and_set_bit(l1bit,
+				   &vcpu_info->evtchn_pending_sel))
+		vcpu_info->evtchn_upcall_pending = 1;
+}
+
 static void unmask_evtchn(int port)
 {
 	unsigned int cpu = get_cpu();
@@ -411,6 +439,9 @@ static void unmask_evtchn(int port)
 		case 2:
 			__unmask_local_port_l2(port);
 			break;
+		case 3:
+			__unmask_local_port_l3(port);
+			break;
 		default:
 			BUG();
 		}
@@ -1185,6 +1216,7 @@ void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
 }
 
 static irqreturn_t xen_debug_interrupt_l2(int irq, void *dev_id);
+static irqreturn_t xen_debug_interrupt_l3(int irq, void *dev_id);
 
 irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
 {
@@ -1215,6 +1247,9 @@ irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
 	case 2:
 		rc = xen_debug_interrupt_l2(irq, dev_id);
 		break;
+	case 3:
+		rc = xen_debug_interrupt_l3(irq, dev_id);
+		break;
 	default:
 		BUG();
 	}
@@ -1285,8 +1320,109 @@ static irqreturn_t xen_debug_interrupt_l2(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+static irqreturn_t xen_debug_interrupt_l3(int irq, void *dev_id)
+{
+	int cpu = smp_processor_id();
+	unsigned long *cpu_evtchn = per_cpu(cpu_evtchn_mask, cpu);
+	unsigned long nr_elems = NR_EVENT_CHANNELS_L3 / BITS_PER_LONG;
+	int i;
+	struct vcpu_info *v;
+
+	v = per_cpu(xen_vcpu, cpu);
+
+	printk(KERN_DEBUG "\npending (only show words which have bits set to 1):\n   ");
+	for (i = nr_elems-1; i >= 0; i--)
+		if (evtchn_pending[i] != 0UL) {
+			printk(KERN_DEBUG " word index %d %0*lx\n",
+			       i,
+			       (int)sizeof(evtchn_pending[0])*2,
+			       evtchn_pending[i]);
+		}
+
+	printk(KERN_DEBUG "\nglobal mask (only show words which have bits set to 0):\n   ");
+	for (i = nr_elems-1; i >= 0; i--)
+		if (evtchn_mask[i] != ~0UL) {
+			printk(KERN_DEBUG " word index %d %0*lx\n",
+			       i,
+			       (int)sizeof(evtchn_mask[0])*2,
+			       evtchn_mask[i]);
+		}
+
+	printk(KERN_DEBUG "\nglobally unmasked (only show result words which have bits set to 1):\n   ");
+	for (i = nr_elems-1; i >= 0; i--)
+		if ((evtchn_pending[i] & ~evtchn_mask[i]) != 0UL) {
+			printk(KERN_DEBUG " word index %d %0*lx\n",
+			       i,
+			       (int)(sizeof(evtchn_mask[0])*2),
+			       evtchn_pending[i] & ~evtchn_mask[i]);
+		}
+
+	printk(KERN_DEBUG "\nlocal cpu%d mask (only show words which have bits set to 1):\n   ", cpu);
+	for (i = (NR_EVENT_CHANNELS_L3/BITS_PER_LONG)-1; i >= 0; i--)
+		if (cpu_evtchn[i] != 0UL) {
+			printk(KERN_DEBUG " word index %d %0*lx\n",
+			       i,
+			       (int)(sizeof(cpu_evtchn[0])*2),
+			       cpu_evtchn[i]);
+		}
+
+	printk(KERN_DEBUG "\nlocally unmasked (only show result words which have bits set to 1):\n   ");
+	for (i = nr_elems-1; i >= 0; i--) {
+		unsigned long pending = evtchn_pending[i]
+			& ~evtchn_mask[i]
+			& cpu_evtchn[i];
+		if (pending != 0UL) {
+			printk(KERN_DEBUG " word index %d %0*lx\n",
+			       i,
+			       (int)(sizeof(evtchn_mask[0])*2),
+			       pending);
+		}
+	}
+
+	printk(KERN_DEBUG "\npending list:\n");
+	for (i = 0; i < NR_EVENT_CHANNELS_L3; i++) {
+		if (sync_test_bit(i, evtchn_pending)) {
+			int word_idx = i / (BITS_PER_LONG * BITS_PER_LONG);
+			int word_idx_l2 = i / BITS_PER_LONG;
+			printk(KERN_DEBUG "  %d: event %d -> irq %d%s%s%s%s\n",
+			       cpu_from_evtchn(i), i,
+			       evtchn_to_irq[i],
+			       !sync_test_bit(word_idx, &v->evtchn_pending_sel)
+			       ? "" : " l1-clear",
+			       !sync_test_bit(word_idx_l2, per_cpu(evtchn_sel_l2, cpu))
+			       ? "" : " l2-clear",
+			       sync_test_bit(i, evtchn_mask)
+			       ? "" : " globally-masked",
+			       sync_test_bit(i, cpu_evtchn)
+			       ? "" : " locally-masked");
+		}
+	}
+
+	return IRQ_HANDLED;
+}
+
+/* The following per-cpu variables are used to save current state of event
+ * processing loop.
+ *
+ * 2-level event channel:
+ *  current_word_idx is the bit index in L1 selector indicating the currently
+ *  processing word in shared bitmap.
+ *  current_bit_idx is the bit index in the currently processing word in shared
+ *  bitmap.
+ *  N.B. current_word_idx_l2 is not used.
+ *
+ * 3-level event channel:
+ *  current_word_idx is the bit index in L1 selector indicating the currently
+ *  processing word in L2 selector.
+ *  current_word_idx_l2 is the bit index in L2 selector word indicating the
+ *  currently processing word in shared bitmap.
+ *  current_bit_idx is the bit index in the currently processing word in shared
+ *  bitmap.
+ *
+ */
 static DEFINE_PER_CPU(unsigned, xed_nesting_count);
 static DEFINE_PER_CPU(unsigned int, current_word_idx);
+static DEFINE_PER_CPU(unsigned int, current_word_idx_l2);
 static DEFINE_PER_CPU(unsigned int, current_bit_idx);
 
 /*
@@ -1409,6 +1545,155 @@ out:
 	put_cpu();
 }
 
+/*
+ * In the 3-level event channel implementation, the first level is a
+ * bitset of words which contain pending bits in the second level.
+ * The second level is another bitsets which contain pending bits in
+ * the third level.  The third level is a bit set of pending events
+ * themselves.
+ */
+static void __xen_evtchn_do_upcall_l3(void)
+{
+	struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
+	unsigned count;
+	int start_word_idx_l1, start_word_idx_l2, start_bit_idx;
+	int word_idx_l1, word_idx_l2, bit_idx;
+	int i, j;
+	int cpu = get_cpu();
+
+	do {
+		unsigned long pending_words_l1;
+
+		vcpu_info->evtchn_upcall_pending = 0;
+
+		if (__this_cpu_inc_return(xed_nesting_count) - 1)
+			goto out;
+#ifndef CONFIG_X86
+		/* No need for a barrier -- XCHG is a barrier on x86. */
+		/* Clear master flag /before/ clearing selector flag. */
+		wmb();
+#endif
+		/* here we get l1 pending selector */
+		pending_words_l1 = xchg(&vcpu_info->evtchn_pending_sel, 0);
+
+		start_word_idx_l1 = __this_cpu_read(current_word_idx);
+		start_word_idx_l2 = __this_cpu_read(current_word_idx_l2);
+		start_bit_idx = __this_cpu_read(current_bit_idx);
+
+		word_idx_l1 = start_word_idx_l1;
+
+		/* loop through l1, try to pick up l2 */
+		for (i = 0; pending_words_l1 != 0; i++) {
+			unsigned long words_l1;
+			unsigned long pending_words_l2;
+
+			words_l1 = MASK_LSBS(pending_words_l1, word_idx_l1);
+
+			if (words_l1 == 0) {
+				word_idx_l1 = 0;
+				start_word_idx_l2 = 0;
+				continue;
+			}
+
+			word_idx_l1 = __ffs(words_l1);
+
+			pending_words_l2 =
+				xchg(&per_cpu(evtchn_sel_l2, cpu)[word_idx_l1],
+				     0);
+
+			word_idx_l2 = 0;
+			if (word_idx_l1 == start_word_idx_l1) {
+				if (i == 0)
+					word_idx_l2 = start_word_idx_l2;
+				else
+					word_idx_l2 &= (1UL << start_word_idx_l2) - 1;
+			}
+
+			for (j = 0; pending_words_l2 != 0; j++) {
+				unsigned long pending_bits;
+				unsigned long words_l2;
+				unsigned long idx;
+
+				words_l2 = MASK_LSBS(pending_words_l2,
+						     word_idx_l2);
+
+				if (words_l2 == 0) {
+					word_idx_l2 = 0;
+					bit_idx = 0;
+					continue;
+				}
+
+				word_idx_l2 = __ffs(words_l2);
+
+				idx = word_idx_l1*BITS_PER_LONG+word_idx_l2;
+				pending_bits =
+					active_evtchns(cpu, idx);
+
+				bit_idx = 0;
+				if (word_idx_l2 == start_word_idx_l2) {
+					if (j == 0)
+						bit_idx = start_bit_idx;
+					else
+						bit_idx &= (1UL<<start_bit_idx)-1;
+				}
+
+				/* process port */
+				do {
+					unsigned long bits;
+					int port, irq;
+					struct irq_desc *desc;
+
+					bits = MASK_LSBS(pending_bits, bit_idx);
+
+					if (bits == 0)
+						break;
+
+					bit_idx = __ffs(bits);
+
+					port = (word_idx_l1 << (LONG_BITORDER << 1)) +
+						(word_idx_l2 << LONG_BITORDER) +
+						bit_idx;
+
+					irq = evtchn_to_irq[port];
+
+					if (irq != -1) {
+						desc = irq_to_desc(irq);
+						if (desc)
+							generic_handle_irq_desc(irq, desc);
+					}
+
+					bit_idx = (bit_idx + 1) % BITS_PER_LONG;
+
+					__this_cpu_write(current_bit_idx, bit_idx);
+					__this_cpu_write(current_word_idx_l2,
+							 bit_idx ? word_idx_l2 :
+							 (word_idx_l2+1) % BITS_PER_LONG);
+					__this_cpu_write(current_word_idx_l2,
+							 word_idx_l2 ? word_idx_l1 :
+							 (word_idx_l1+1) % BITS_PER_LONG);
+				} while (bit_idx != 0);
+
+				if ((word_idx_l2 != start_word_idx_l2) || (j != 0))
+					pending_words_l2 &= ~(1UL << word_idx_l2);
+
+				word_idx_l2 = (word_idx_l2 + 1) % BITS_PER_LONG;
+			}
+
+			if ((word_idx_l1 != start_word_idx_l1) || (i != 0))
+				pending_words_l1 &= ~(1UL << word_idx_l1);
+
+			word_idx_l1 = (word_idx_l1 + 1) % BITS_PER_LONG;
+		}
+
+		BUG_ON(!irqs_disabled());
+		count = __this_cpu_read(xed_nesting_count);
+		__this_cpu_write(xed_nesting_count, 0);
+	} while (count != 1 || vcpu_info->evtchn_upcall_pending);
+
+out:
+	put_cpu();
+}
+
 void xen_evtchn_do_upcall(struct pt_regs *regs)
 {
 	struct pt_regs *old_regs = set_irq_regs(regs);
@@ -1420,6 +1705,9 @@ void xen_evtchn_do_upcall(struct pt_regs *regs)
 	case 2:
 		__xen_evtchn_do_upcall_l2();
 		break;
+	case 3:
+		__xen_evtchn_do_upcall_l3();
+		break;
 	default:
 		BUG();
 	}
@@ -1434,6 +1722,9 @@ void xen_hvm_evtchn_do_upcall(void)
 	case 2:
 		__xen_evtchn_do_upcall_l2();
 		break;
+	case 3:
+		__xen_evtchn_do_upcall_l3();
+		break;
 	default:
 		BUG();
 	}
-- 
1.7.10.4