/* * CDDL HEADER START * * The contents of this file are subject to the terms of the * Common Development and Distribution License (the "License"). * You may not use this file except in compliance with the License. * * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE * or http://www.opensolaris.org/os/licensing. * See the License for the specific language governing permissions * and limitations under the License. * * When distributing Covered Code, include this CDDL HEADER in each * file and include the License file at usr/src/OPENSOLARIS.LICENSE. * If applicable, add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your own identifying * information: Portions Copyright [yyyy] [name of copyright owner] * * CDDL HEADER END */ /* * Copyright 2009 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Implementation for cross-processor calls via interprocessor interrupts * * This implementation uses a message passing architecture to allow multiple * concurrent cross calls to be in flight at any given time. We use the cmpxchg * instruction, aka casptr(), to implement simple efficient work queues for * message passing between CPUs with almost no need for regular locking. * See xc_extract() and xc_insert() below. * * The general idea is that initiating a cross call means putting a message * on a target(s) CPU's work queue. Any synchronization is handled by passing * the message back and forth between initiator and target(s). * * Every CPU has xc_work_cnt, which indicates it has messages to process. * This value is incremented as message traffic is initiated and decremented * with every message that finishes all processing. * * The code needs no mfence or other membar_*() calls. The uses of * casptr(), cas32() and atomic_dec_32() for the message passing are * implemented with LOCK prefix instructions which are equivalent to mfence. * * One interesting aspect of this implmentation is that it allows 2 or more * CPUs to initiate cross calls to intersecting sets of CPUs at the same time. * The cross call processing by the CPUs will happen in any order with only * a guarantee, for xc_call() and xc_sync(), that an initiator won't return * from cross calls before all slaves have invoked the function. * * The reason for this asynchronous approach is to allow for fast global * TLB shootdowns. If all CPUs, say N, tried to do a global TLB invalidation * on a different Virtual Address at the same time. The old code required * N squared IPIs. With this method, depending on timing, it could happen * with just N IPIs. */ /* * The default is to not enable collecting counts of IPI information, since * the updating of shared cachelines could cause excess bus traffic. */ uint_t xc_collect_enable = 0; uint64_t xc_total_cnt = 0; /* total #IPIs sent for cross calls */ uint64_t xc_multi_cnt = 0; /* # times we piggy backed on another IPI */ /* * Values for message states. Here are the normal transitions. A transition * of "->" happens in the slave cpu and "=>" happens in the master cpu as * the messages are passed back and forth. * * FREE => ASYNC -> DONE => FREE * FREE => CALL -> DONE => FREE * FREE => SYNC -> WAITING => RELEASED -> DONE => FREE * * The interesing one above is ASYNC. You might ask, why not go directly * to FREE, instead of DONE. If it did that, it might be possible to exhaust * the master's xc_free list if a master can generate ASYNC messages faster * then the slave can process them. That could be handled with more complicated * handling. However since nothing important uses ASYNC, I've not bothered. */ #define XC_MSG_FREE (0) /* msg in xc_free queue */ #define XC_MSG_ASYNC (1) /* msg in slave xc_msgbox */ #define XC_MSG_CALL (2) /* msg in slave xc_msgbox */ #define XC_MSG_SYNC (3) /* msg in slave xc_msgbox */ #define XC_MSG_WAITING (4) /* msg in master xc_msgbox or xc_waiters */ #define XC_MSG_RELEASED (5) /* msg in slave xc_msgbox */ #define XC_MSG_DONE (6) /* msg in master xc_msgbox */ /* * We allow for one high priority message at a time to happen in the system. * This is used for panic, kmdb, etc., so no locking is done. */ static volatile cpuset_t xc_priority_set_store; static volatile ulong_t *xc_priority_set = CPUSET2BV(xc_priority_set_store); static xc_data_t xc_priority_data; /* * Wrappers to avoid C compiler warnings due to volatile. The atomic bit * operations don't accept volatile bit vectors - which is a bit silly. */ #define XC_BT_SET(vector, b) BT_ATOMIC_SET((ulong_t *)(vector), (b)) #define XC_BT_CLEAR(vector, b) BT_ATOMIC_CLEAR((ulong_t *)(vector), (b)) /* * Decrement a CPU's work count */ static void xc_decrement(struct machcpu *mcpu) { atomic_dec_32(&mcpu->xc_work_cnt); } /* * Increment a CPU's work count and return the old value */ static int xc_increment(struct machcpu *mcpu) { int old; do { old = mcpu->xc_work_cnt; } while (cas32((uint32_t *)&mcpu->xc_work_cnt, old, old + 1) != old); return (old); } /* * Put a message into a queue. The insertion is atomic no matter * how many different inserts/extracts to the same queue happen. */ static void xc_insert(void *queue, xc_msg_t *msg) { xc_msg_t *old_head; do { old_head = (xc_msg_t *)*(volatile xc_msg_t **)queue; msg->xc_next = old_head; } while (casptr(queue, old_head, msg) != old_head); } /* * Extract a message from a queue. The extraction is atomic only * when just one thread does extractions from the queue. * If the queue is empty, NULL is returned. */ static xc_msg_t * xc_extract(xc_msg_t **queue) { xc_msg_t *old_head; do { old_head = (xc_msg_t *)*(volatile xc_msg_t **)queue; if (old_head == NULL) return (old_head); } while (casptr(queue, old_head, old_head->xc_next) != old_head); old_head->xc_next = NULL; return (old_head); } /* * Initialize the machcpu fields used for cross calls */ static uint_t xc_initialized = 0; void xc_init_cpu(struct cpu *cpup) { xc_msg_t *msg; int c; /* * add a new msg to each existing CPU's free list, as well as one for * my list for each of them */ for (c = 0; c < ncpus; ++c) { if (cpu[c] == NULL) continue; msg = kmem_zalloc(sizeof (*msg), KM_SLEEP); msg->xc_command = XC_MSG_FREE; xc_insert(&cpu[c]->cpu_m.xc_free, msg); msg = kmem_zalloc(sizeof (*msg), KM_SLEEP); msg->xc_command = XC_MSG_FREE; xc_insert(&cpup->cpu_m.xc_free, msg); } /* * Add one for self messages */ msg = kmem_zalloc(sizeof (*msg), KM_SLEEP); msg->xc_command = XC_MSG_FREE; xc_insert(&cpup->cpu_m.xc_free, msg); if (!xc_initialized) xc_initialized = 1; } /* * X-call message processing routine. Note that this is used by both * senders and recipients of messages. * * We're protected against changing CPUs by either being in a high-priority * interrupt, having preemption disabled or by having a raised SPL. */ /*ARGSUSED*/ uint_t xc_serv(caddr_t arg1, caddr_t arg2) { struct machcpu *mcpup = &(CPU->cpu_m); xc_msg_t *msg; xc_data_t *data; xc_msg_t *xc_waiters = NULL; uint32_t num_waiting = 0; xc_func_t func; xc_arg_t a1; xc_arg_t a2; xc_arg_t a3; uint_t rc = DDI_INTR_UNCLAIMED; while (mcpup->xc_work_cnt != 0) { rc = DDI_INTR_CLAIMED; /* * We may have to wait for a message to arrive. */ for (;;) { /* * Alway check for and handle a priority message. */ if (BT_TEST(xc_priority_set, CPU->cpu_id)) { func = xc_priority_data.xc_func; a1 = xc_priority_data.xc_a1; a2 = xc_priority_data.xc_a2; a3 = xc_priority_data.xc_a3; XC_BT_CLEAR(xc_priority_set, CPU->cpu_id); xc_decrement(mcpup); func(a1, a2, a3); if (mcpup->xc_work_cnt == 0) return (rc); } /* * extract and handle regular message */ msg = xc_extract(&mcpup->xc_msgbox); if (msg != NULL) break; /* * wait for a message to arrive */ if (x86_feature & X86_MWAIT) { i86_monitor( (volatile uint32_t *)&mcpup->xc_msgbox, 0, 0); if (mcpup->xc_msgbox == NULL) i86_mwait(0, 0); } else { SMT_PAUSE(); } } /* * process the message */ switch (msg->xc_command) { /* * ASYNC gives back the message immediately, then we do the * function and return with no more waiting. */ case XC_MSG_ASYNC: data = &cpu[msg->xc_master]->cpu_m.xc_data; func = data->xc_func; a1 = data->xc_a1; a2 = data->xc_a2; a3 = data->xc_a3; msg->xc_command = XC_MSG_DONE; xc_insert(&cpu[msg->xc_master]->cpu_m.xc_msgbox, msg); if (func != NULL) (void) (*func)(a1, a2, a3); xc_decrement(mcpup); break; /* * SYNC messages do the call, then send it back to the master * in WAITING mode */ case XC_MSG_SYNC: data = &cpu[msg->xc_master]->cpu_m.xc_data; if (data->xc_func != NULL) (void) (*data->xc_func)(data->xc_a1, data->xc_a2, data->xc_a3); msg->xc_command = XC_MSG_WAITING; xc_insert(&cpu[msg->xc_master]->cpu_m.xc_msgbox, msg); break; /* * WAITING messsages are collected by the master until all * have arrived. Once all arrive, we release them back to * the slaves */ case XC_MSG_WAITING: xc_insert(&xc_waiters, msg); if (++num_waiting < mcpup->xc_wait_cnt) break; while ((msg = xc_extract(&xc_waiters)) != NULL) { msg->xc_command = XC_MSG_RELEASED; xc_insert(&cpu[msg->xc_slave]->cpu_m.xc_msgbox, msg); --num_waiting; } if (num_waiting != 0) panic("wrong number waiting"); mcpup->xc_wait_cnt = 0; break; /* * CALL messages do the function and then, like RELEASE, * send the message is back to master as DONE. */ case XC_MSG_CALL: data = &cpu[msg->xc_master]->cpu_m.xc_data; if (data->xc_func != NULL) (void) (*data->xc_func)(data->xc_a1, data->xc_a2, data->xc_a3); /*FALLTHROUGH*/ case XC_MSG_RELEASED: msg->xc_command = XC_MSG_DONE; xc_insert(&cpu[msg->xc_master]->cpu_m.xc_msgbox, msg); xc_decrement(mcpup); break; /* * DONE means a slave has completely finished up. * Once we collect all the DONE messages, we'll exit * processing too. */ case XC_MSG_DONE: msg->xc_command = XC_MSG_FREE; xc_insert(&mcpup->xc_free, msg); xc_decrement(mcpup); break; case XC_MSG_FREE: panic("free message in msgbox"); break; default: panic("bad message in msgbox"); break; } } return (rc); } /* * Initiate cross call processing. */ static void xc_common( xc_func_t func, xc_arg_t arg1, xc_arg_t arg2, xc_arg_t arg3, ulong_t *set, uint_t command) { int c; struct cpu *cpup; xc_msg_t *msg; xc_data_t *data; int cnt; int save_spl; if (!xc_initialized) { if (BT_TEST(set, CPU->cpu_id) && (CPU->cpu_flags & CPU_READY) && func != NULL) (void) (*func)(arg1, arg2, arg3); return; } save_spl = splr(ipltospl(XC_HI_PIL)); /* * fill in cross call data */ data = &CPU->cpu_m.xc_data; data->xc_func = func; data->xc_a1 = arg1; data->xc_a2 = arg2; data->xc_a3 = arg3; /* * Post messages to all CPUs involved that are CPU_READY */ CPU->cpu_m.xc_wait_cnt = 0; for (c = 0; c < ncpus; ++c) { if (!BT_TEST(set, c)) continue; cpup = cpu[c]; if (cpup == NULL || !(cpup->cpu_flags & CPU_READY)) continue; /* * Fill out a new message. */ msg = xc_extract(&CPU->cpu_m.xc_free); if (msg == NULL) panic("Ran out of free xc_msg_t's"); msg->xc_command = command; msg->xc_master = CPU->cpu_id; msg->xc_slave = c; /* * Increment my work count for all messages that I'll * transition from DONE to FREE. * Also remember how many XC_MSG_WAITINGs to look for */ (void) xc_increment(&CPU->cpu_m); if (command == XC_MSG_SYNC) ++CPU->cpu_m.xc_wait_cnt; /* * Increment the target CPU work count then insert the message * in the target msgbox. If I post the first bit of work * for the target to do, send an IPI to the target CPU. */ cnt = xc_increment(&cpup->cpu_m); xc_insert(&cpup->cpu_m.xc_msgbox, msg); if (cpup != CPU) { if (cnt == 0) { CPU_STATS_ADDQ(CPU, sys, xcalls, 1); send_dirint(c, XC_HI_PIL); if (xc_collect_enable) ++xc_total_cnt; } else if (xc_collect_enable) { ++xc_multi_cnt; } } } /* * Now drop into the message handler until all work is done */ (void) xc_serv(NULL, NULL); splx(save_spl); } /* * Push out a priority cross call. */ static void xc_priority_common( xc_func_t func, xc_arg_t arg1, xc_arg_t arg2, xc_arg_t arg3, ulong_t *set) { int i; int c; struct cpu *cpup; /* * Wait briefly for any previous xc_priority to have finished. */ for (c = 0; c < ncpus; ++c) { cpup = cpu[c]; if (cpup == NULL || !(cpup->cpu_flags & CPU_READY)) continue; /* * The value of 40000 here is from old kernel code. It * really should be changed to some time based value, since * under a hypervisor, there's no guarantee a remote CPU * is even scheduled. */ for (i = 0; BT_TEST(xc_priority_set, c) && i < 40000; ++i) SMT_PAUSE(); /* * Some CPU did not respond to a previous priority request. It's * probably deadlocked with interrupts blocked or some such * problem. We'll just erase the previous request - which was * most likely a kmdb_enter that has already expired - and plow * ahead. */ if (BT_TEST(xc_priority_set, c)) { XC_BT_CLEAR(xc_priority_set, c); if (cpup->cpu_m.xc_work_cnt > 0) xc_decrement(&cpup->cpu_m); } } /* * fill in cross call data */ xc_priority_data.xc_func = func; xc_priority_data.xc_a1 = arg1; xc_priority_data.xc_a2 = arg2; xc_priority_data.xc_a3 = arg3; /* * Post messages to all CPUs involved that are CPU_READY * We'll always IPI, plus bang on the xc_msgbox for i86_mwait() */ for (c = 0; c < ncpus; ++c) { if (!BT_TEST(set, c)) continue; cpup = cpu[c]; if (cpup == NULL || !(cpup->cpu_flags & CPU_READY) || cpup == CPU) continue; (void) xc_increment(&cpup->cpu_m); XC_BT_SET(xc_priority_set, c); send_dirint(c, XC_HI_PIL); for (i = 0; i < 10; ++i) { (void) casptr(&cpup->cpu_m.xc_msgbox, cpup->cpu_m.xc_msgbox, cpup->cpu_m.xc_msgbox); } } } /* * Do cross call to all other CPUs with absolutely no waiting or handshaking. * This should only be used for extraordinary operations, like panic(), which * need to work, in some fashion, in a not completely functional system. * All other uses that want minimal waiting should use xc_call_nowait(). */ void xc_priority( xc_arg_t arg1, xc_arg_t arg2, xc_arg_t arg3, ulong_t *set, xc_func_t func) { extern int IGNORE_KERNEL_PREEMPTION; int save_spl = splr(ipltospl(XC_HI_PIL)); int save_kernel_preemption = IGNORE_KERNEL_PREEMPTION; IGNORE_KERNEL_PREEMPTION = 1; xc_priority_common((xc_func_t)func, arg1, arg2, arg3, set); IGNORE_KERNEL_PREEMPTION = save_kernel_preemption; splx(save_spl); } /* * Wrapper for kmdb to capture other CPUs, causing them to enter the debugger. */ void kdi_xc_others(int this_cpu, void (*func)(void)) { extern int IGNORE_KERNEL_PREEMPTION; int save_kernel_preemption; cpuset_t set; if (!xc_initialized) return; save_kernel_preemption = IGNORE_KERNEL_PREEMPTION; IGNORE_KERNEL_PREEMPTION = 1; CPUSET_ALL_BUT(set, this_cpu); xc_priority_common((xc_func_t)func, 0, 0, 0, CPUSET2BV(set)); IGNORE_KERNEL_PREEMPTION = save_kernel_preemption; } /* * Invoke function on specified processors. Remotes may continue after * service with no waiting. xc_call_nowait() may return immediately too. */ void xc_call_nowait( xc_arg_t arg1, xc_arg_t arg2, xc_arg_t arg3, ulong_t *set, xc_func_t func) { xc_common(func, arg1, arg2, arg3, set, XC_MSG_ASYNC); } /* * Invoke function on specified processors. Remotes may continue after * service with no waiting. xc_call() returns only after remotes have finished. */ void xc_call( xc_arg_t arg1, xc_arg_t arg2, xc_arg_t arg3, ulong_t *set, xc_func_t func) { xc_common(func, arg1, arg2, arg3, set, XC_MSG_CALL); } /* * Invoke function on specified processors. Remotes wait until all have * finished. xc_sync() also waits until all remotes have finished. */ void xc_sync( xc_arg_t arg1, xc_arg_t arg2, xc_arg_t arg3, ulong_t *set, xc_func_t func) { xc_common(func, arg1, arg2, arg3, set, XC_MSG_SYNC); }