arch/x86/xen/multicalls.c - kernel/msm-4.9 - Gitiles

 /*
  * Xen hypercall batching.
  *
  * Xen allows multiple hypercalls to be issued at once, using the
  * multicall interface.  This allows the cost of trapping into the
  * hypervisor to be amortized over several calls.
  *
  * This file implements a simple interface for multicalls.  There's a
  * per-cpu buffer of outstanding multicalls.  When you want to queue a
  * multicall for issuing, you can allocate a multicall slot for the
  * call and its arguments, along with storage for space which is
  * pointed to by the arguments (for passing pointers to structures,
  * etc).  When the multicall is actually issued, all the space for the
  * commands and allocated memory is freed for reuse.
  *
  * Multicalls are flushed whenever any of the buffers get full, or
  * when explicitly requested.  There's no way to get per-multicall
  * return results back.  It will BUG if any of the multicalls fail.
  *
  * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
  */
 #include <linux/percpu.h>
 #include <linux/hardirq.h>
 #include <linux/debugfs.h>

 #include <asm/xen/hypercall.h>

 #include "multicalls.h"
 #include "debugfs.h"

 #define MC_BATCH	32

 #define MC_DEBUG	1

 #define MC_ARGS		(MC_BATCH * 16)


 struct mc_buffer {
 	struct multicall_entry entries[MC_BATCH];
 #if MC_DEBUG
 	struct multicall_entry debug[MC_BATCH];
 	void *caller[MC_BATCH];
 #endif
 	unsigned char args[MC_ARGS];
 	struct callback {
 		void (*fn)(void *);
 		void *data;
 	} callbacks[MC_BATCH];
 	unsigned mcidx, argidx, cbidx;
 };

 static DEFINE_PER_CPU(struct mc_buffer, mc_buffer);
 DEFINE_PER_CPU(unsigned long, xen_mc_irq_flags);

 /* flush reasons 0- slots, 1- args, 2- callbacks */
 enum flush_reasons
 {
 	FL_SLOTS,
 	FL_ARGS,
 	FL_CALLBACKS,

 	FL_N_REASONS
 };

 #ifdef CONFIG_XEN_DEBUG_FS
 #define NHYPERCALLS	40		/* not really */

 static struct {
 	unsigned histo[MC_BATCH+1];

 	unsigned issued;
 	unsigned arg_total;
 	unsigned hypercalls;
 	unsigned histo_hypercalls[NHYPERCALLS];

 	unsigned flush[FL_N_REASONS];
 } mc_stats;

 static u8 zero_stats;

 static inline void check_zero(void)
 {
 	if (unlikely(zero_stats)) {
 		memset(&mc_stats, 0, sizeof(mc_stats));
 		zero_stats = 0;
 	}
 }

 static void mc_add_stats(const struct mc_buffer *mc)
 {
 	int i;

 	check_zero();

 	mc_stats.issued++;
 	mc_stats.hypercalls += mc->mcidx;
 	mc_stats.arg_total += mc->argidx;

 	mc_stats.histo[mc->mcidx]++;
 	for(i = 0; i < mc->mcidx; i++) {
 		unsigned op = mc->entries[i].op;
 		if (op < NHYPERCALLS)
 			mc_stats.histo_hypercalls[op]++;
 	}
 }

 static void mc_stats_flush(enum flush_reasons idx)
 {
 	check_zero();

 	mc_stats.flush[idx]++;
 }

 #else  /* !CONFIG_XEN_DEBUG_FS */

 static inline void mc_add_stats(const struct mc_buffer *mc)
 {
 }

 static inline void mc_stats_flush(enum flush_reasons idx)
 {
 }
 #endif	/* CONFIG_XEN_DEBUG_FS */

 void xen_mc_flush(void)
 {
 	struct mc_buffer *b = &__get_cpu_var(mc_buffer);
 	int ret = 0;
 	unsigned long flags;
 	int i;

 	BUG_ON(preemptible());

 	/* Disable interrupts in case someone comes in and queues
 	   something in the middle */
 	local_irq_save(flags);

 	mc_add_stats(b);

 	if (b->mcidx) {
 #if MC_DEBUG
 		memcpy(b->debug, b->entries,
 		       b->mcidx * sizeof(struct multicall_entry));
 #endif

 		if (HYPERVISOR_multicall(b->entries, b->mcidx) != 0)
 			BUG();
 		for (i = 0; i < b->mcidx; i++)
 			if (b->entries[i].result < 0)
 				ret++;

 #if MC_DEBUG
 		if (ret) {
 			printk(KERN_ERR "%d multicall(s) failed: cpu %d\n",
 			       ret, smp_processor_id());
 			dump_stack();
 			for (i = 0; i < b->mcidx; i++) {
 				printk(KERN_DEBUG "  call %2d/%d: op=%lu arg=[%lx] result=%ld\t%pF\n",
 				       i+1, b->mcidx,
 				       b->debug[i].op,
 				       b->debug[i].args[0],
 				       b->entries[i].result,
 				       b->caller[i]);
 			}
 		}
 #endif

 		b->mcidx = 0;
 		b->argidx = 0;
 	} else
 		BUG_ON(b->argidx != 0);

 	for (i = 0; i < b->cbidx; i++) {
 		struct callback *cb = &b->callbacks[i];

 		(*cb->fn)(cb->data);
 	}
 	b->cbidx = 0;

 	local_irq_restore(flags);

 	WARN_ON(ret);
 }

 struct multicall_space __xen_mc_entry(size_t args)
 {
 	struct mc_buffer *b = &__get_cpu_var(mc_buffer);
 	struct multicall_space ret;
 	unsigned argidx = roundup(b->argidx, sizeof(u64));

 	BUG_ON(preemptible());
 	BUG_ON(b->argidx >= MC_ARGS);

 	if (b->mcidx == MC_BATCH ||
 	    (argidx + args) >= MC_ARGS) {
 		mc_stats_flush(b->mcidx == MC_BATCH ? FL_SLOTS : FL_ARGS);
 		xen_mc_flush();
 		argidx = roundup(b->argidx, sizeof(u64));
 	}

 	ret.mc = &b->entries[b->mcidx];
 #ifdef MC_DEBUG
 	b->caller[b->mcidx] = __builtin_return_address(0);
 #endif
 	b->mcidx++;
 	ret.args = &b->args[argidx];
 	b->argidx = argidx + args;

 	BUG_ON(b->argidx >= MC_ARGS);
 	return ret;
 }

 struct multicall_space xen_mc_extend_args(unsigned long op, size_t size)
 {
 	struct mc_buffer *b = &__get_cpu_var(mc_buffer);
 	struct multicall_space ret = { NULL, NULL };

 	BUG_ON(preemptible());
 	BUG_ON(b->argidx >= MC_ARGS);

 	if (b->mcidx == 0)
 		return ret;

 	if (b->entries[b->mcidx - 1].op != op)
 		return ret;

 	if ((b->argidx + size) >= MC_ARGS)
 		return ret;

 	ret.mc = &b->entries[b->mcidx - 1];
 	ret.args = &b->args[b->argidx];
 	b->argidx += size;

 	BUG_ON(b->argidx >= MC_ARGS);
 	return ret;
 }

 void xen_mc_callback(void (*fn)(void *), void *data)
 {
 	struct mc_buffer *b = &__get_cpu_var(mc_buffer);
 	struct callback *cb;

 	if (b->cbidx == MC_BATCH) {
 		mc_stats_flush(FL_CALLBACKS);
 		xen_mc_flush();
 	}

 	cb = &b->callbacks[b->cbidx++];
 	cb->fn = fn;
 	cb->data = data;
 }

 #ifdef CONFIG_XEN_DEBUG_FS

 static struct dentry *d_mc_debug;

 static int __init xen_mc_debugfs(void)
 {
 	struct dentry *d_xen = xen_init_debugfs();

 	if (d_xen == NULL)
 		return -ENOMEM;

 	d_mc_debug = debugfs_create_dir("multicalls", d_xen);

 	debugfs_create_u8("zero_stats", 0644, d_mc_debug, &zero_stats);

 	debugfs_create_u32("batches", 0444, d_mc_debug, &mc_stats.issued);
 	debugfs_create_u32("hypercalls", 0444, d_mc_debug, &mc_stats.hypercalls);
 	debugfs_create_u32("arg_total", 0444, d_mc_debug, &mc_stats.arg_total);

 	xen_debugfs_create_u32_array("batch_histo", 0444, d_mc_debug,
 				     mc_stats.histo, MC_BATCH);
 	xen_debugfs_create_u32_array("hypercall_histo", 0444, d_mc_debug,
 				     mc_stats.histo_hypercalls, NHYPERCALLS);
 	xen_debugfs_create_u32_array("flush_reasons", 0444, d_mc_debug,
 				     mc_stats.flush, FL_N_REASONS);

 	return 0;
 }
 fs_initcall(xen_mc_debugfs);

 #endif	/* CONFIG_XEN_DEBUG_FS */
	/*
	* Xen hypercall batching.
	*
	* Xen allows multiple hypercalls to be issued at once, using the
	* multicall interface. This allows the cost of trapping into the
	* hypervisor to be amortized over several calls.
	*
	* This file implements a simple interface for multicalls. There's a
	* per-cpu buffer of outstanding multicalls. When you want to queue a
	* multicall for issuing, you can allocate a multicall slot for the
	* call and its arguments, along with storage for space which is
	* pointed to by the arguments (for passing pointers to structures,
	* etc). When the multicall is actually issued, all the space for the
	* commands and allocated memory is freed for reuse.
	*
	* Multicalls are flushed whenever any of the buffers get full, or
	* when explicitly requested. There's no way to get per-multicall
	* return results back. It will BUG if any of the multicalls fail.
	*
	* Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
	*/
	#include <linux/percpu.h>
	#include <linux/hardirq.h>
	#include <linux/debugfs.h>

	#include <asm/xen/hypercall.h>

	#include "multicalls.h"
	#include "debugfs.h"

	#define MC_BATCH 32

	#define MC_DEBUG 1

	#define MC_ARGS (MC_BATCH * 16)


	struct mc_buffer {
	struct multicall_entry entries[MC_BATCH];
	#if MC_DEBUG
	struct multicall_entry debug[MC_BATCH];
	void *caller[MC_BATCH];
	#endif
	unsigned char args[MC_ARGS];
	struct callback {
	void (fn)(void );
	void *data;
	} callbacks[MC_BATCH];
	unsigned mcidx, argidx, cbidx;
	};

	static DEFINE_PER_CPU(struct mc_buffer, mc_buffer);
	DEFINE_PER_CPU(unsigned long, xen_mc_irq_flags);

	/* flush reasons 0- slots, 1- args, 2- callbacks */
	enum flush_reasons
	{
	FL_SLOTS,
	FL_ARGS,
	FL_CALLBACKS,

	FL_N_REASONS
	};

	#ifdef CONFIG_XEN_DEBUG_FS
	#define NHYPERCALLS 40 /* not really */

	static struct {
	unsigned histo[MC_BATCH+1];

	unsigned issued;
	unsigned arg_total;
	unsigned hypercalls;
	unsigned histo_hypercalls[NHYPERCALLS];

	unsigned flush[FL_N_REASONS];
	} mc_stats;

	static u8 zero_stats;

	static inline void check_zero(void)
	{
	if (unlikely(zero_stats)) {
	memset(&mc_stats, 0, sizeof(mc_stats));
	zero_stats = 0;
	}
	}

	static void mc_add_stats(const struct mc_buffer *mc)
	{
	int i;

	check_zero();

	mc_stats.issued++;
	mc_stats.hypercalls += mc->mcidx;
	mc_stats.arg_total += mc->argidx;

	mc_stats.histo[mc->mcidx]++;
	for(i = 0; i < mc->mcidx; i++) {
	unsigned op = mc->entries[i].op;
	if (op < NHYPERCALLS)
	mc_stats.histo_hypercalls[op]++;
	}
	}

	static void mc_stats_flush(enum flush_reasons idx)
	{
	check_zero();

	mc_stats.flush[idx]++;
	}

	#else /* !CONFIG_XEN_DEBUG_FS */

	static inline void mc_add_stats(const struct mc_buffer *mc)
	{
	}

	static inline void mc_stats_flush(enum flush_reasons idx)
	{
	}
	#endif /* CONFIG_XEN_DEBUG_FS */

	void xen_mc_flush(void)
	{
	struct mc_buffer *b = &__get_cpu_var(mc_buffer);
	int ret = 0;
	unsigned long flags;
	int i;

	BUG_ON(preemptible());

	/* Disable interrupts in case someone comes in and queues
	something in the middle */
	local_irq_save(flags);

	mc_add_stats(b);

	if (b->mcidx) {
	#if MC_DEBUG
	memcpy(b->debug, b->entries,
	b->mcidx * sizeof(struct multicall_entry));
	#endif

	if (HYPERVISOR_multicall(b->entries, b->mcidx) != 0)
	BUG();
	for (i = 0; i < b->mcidx; i++)
	if (b->entries[i].result < 0)
	ret++;

	#if MC_DEBUG
	if (ret) {
	printk(KERN_ERR "%d multicall(s) failed: cpu %d\n",
	ret, smp_processor_id());
	dump_stack();
	for (i = 0; i < b->mcidx; i++) {
	printk(KERN_DEBUG " call %2d/%d: op=%lu arg=[%lx] result=%ld\t%pF\n",
	i+1, b->mcidx,
	b->debug[i].op,
	b->debug[i].args[0],
	b->entries[i].result,
	b->caller[i]);
	}
	}
	#endif

	b->mcidx = 0;
	b->argidx = 0;
	} else
	BUG_ON(b->argidx != 0);

	for (i = 0; i < b->cbidx; i++) {
	struct callback *cb = &b->callbacks[i];

	(*cb->fn)(cb->data);
	}
	b->cbidx = 0;

	local_irq_restore(flags);

	WARN_ON(ret);
	}

	struct multicall_space __xen_mc_entry(size_t args)
	{
	struct mc_buffer *b = &__get_cpu_var(mc_buffer);
	struct multicall_space ret;
	unsigned argidx = roundup(b->argidx, sizeof(u64));

	BUG_ON(preemptible());
	BUG_ON(b->argidx >= MC_ARGS);

	if (b->mcidx == MC_BATCH \|\|
	(argidx + args) >= MC_ARGS) {
	mc_stats_flush(b->mcidx == MC_BATCH ? FL_SLOTS : FL_ARGS);
	xen_mc_flush();
	argidx = roundup(b->argidx, sizeof(u64));
	}

	ret.mc = &b->entries[b->mcidx];
	#ifdef MC_DEBUG
	b->caller[b->mcidx] = __builtin_return_address(0);
	#endif
	b->mcidx++;
	ret.args = &b->args[argidx];
	b->argidx = argidx + args;

	BUG_ON(b->argidx >= MC_ARGS);
	return ret;
	}

	struct multicall_space xen_mc_extend_args(unsigned long op, size_t size)
	{
	struct mc_buffer *b = &__get_cpu_var(mc_buffer);
	struct multicall_space ret = { NULL, NULL };

	BUG_ON(preemptible());
	BUG_ON(b->argidx >= MC_ARGS);

	if (b->mcidx == 0)
	return ret;

	if (b->entries[b->mcidx - 1].op != op)
	return ret;

	if ((b->argidx + size) >= MC_ARGS)
	return ret;

	ret.mc = &b->entries[b->mcidx - 1];
	ret.args = &b->args[b->argidx];
	b->argidx += size;

	BUG_ON(b->argidx >= MC_ARGS);
	return ret;
	}

	void xen_mc_callback(void (fn)(void ), void *data)
	{
	struct mc_buffer *b = &__get_cpu_var(mc_buffer);
	struct callback *cb;

	if (b->cbidx == MC_BATCH) {
	mc_stats_flush(FL_CALLBACKS);
	xen_mc_flush();
	}

	cb = &b->callbacks[b->cbidx++];
	cb->fn = fn;
	cb->data = data;
	}

	#ifdef CONFIG_XEN_DEBUG_FS

	static struct dentry *d_mc_debug;

	static int __init xen_mc_debugfs(void)
	{
	struct dentry *d_xen = xen_init_debugfs();

	if (d_xen == NULL)
	return -ENOMEM;

	d_mc_debug = debugfs_create_dir("multicalls", d_xen);

	debugfs_create_u8("zero_stats", 0644, d_mc_debug, &zero_stats);

	debugfs_create_u32("batches", 0444, d_mc_debug, &mc_stats.issued);
	debugfs_create_u32("hypercalls", 0444, d_mc_debug, &mc_stats.hypercalls);
	debugfs_create_u32("arg_total", 0444, d_mc_debug, &mc_stats.arg_total);

	xen_debugfs_create_u32_array("batch_histo", 0444, d_mc_debug,
	mc_stats.histo, MC_BATCH);
	xen_debugfs_create_u32_array("hypercall_histo", 0444, d_mc_debug,
	mc_stats.histo_hypercalls, NHYPERCALLS);
	xen_debugfs_create_u32_array("flush_reasons", 0444, d_mc_debug,
	mc_stats.flush, FL_N_REASONS);

	return 0;
	}
	fs_initcall(xen_mc_debugfs);

	#endif /* CONFIG_XEN_DEBUG_FS */