[mirror_ubuntu-artful-kernel.git] / arch / x86 / xen / multicalls.c

/*
 * 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 <asm/xen/hypercall.h>

#include "multicalls.h"

#define MC_DEBUG	1

#define MC_BATCH	32
#define MC_ARGS		(MC_BATCH * 16)

struct mc_buffer {
	struct multicall_entry entries[MC_BATCH];
#if MC_DEBUG
	struct multicall_entry debug[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);

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);

	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());
			for (i = 0; i < b->mcidx; i++) {
				printk("  call %2d/%d: op=%lu arg=[%lx] result=%ld\n",
				       i+1, b->mcidx,
				       b->debug[i].op,
				       b->debug[i].args[0],
				       b->entries[i].result);
			}
		}
#endif

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

	local_irq_restore(flags);

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

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

	BUG_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) {
		xen_mc_flush();
		argidx = roundup(b->argidx, sizeof(u64));
	}

	ret.mc = &b->entries[b->mcidx];
	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)
		xen_mc_flush();

	cb = &b->callbacks[b->cbidx++];
	cb->fn = fn;
	cb->data = data;
}
Commit	Line	Data
5ead97c8 JF	1	/*
	2	* Xen hypercall batching.
	3	*
	4	* Xen allows multiple hypercalls to be issued at once, using the
	5	* multicall interface. This allows the cost of trapping into the
	6	* hypervisor to be amortized over several calls.
	7	*
	8	* This file implements a simple interface for multicalls. There's a
	9	* per-cpu buffer of outstanding multicalls. When you want to queue a
	10	* multicall for issuing, you can allocate a multicall slot for the
	11	* call and its arguments, along with storage for space which is
	12	* pointed to by the arguments (for passing pointers to structures,
	13	* etc). When the multicall is actually issued, all the space for the
	14	* commands and allocated memory is freed for reuse.
	15	*
	16	* Multicalls are flushed whenever any of the buffers get full, or
	17	* when explicitly requested. There's no way to get per-multicall
	18	* return results back. It will BUG if any of the multicalls fail.
	19	*
	20	* Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
	21	*/
	22	#include <linux/percpu.h>
f120f13e	23	#include <linux/hardirq.h>
5ead97c8 JF	24
	25	#include <asm/xen/hypercall.h>
	26
	27	#include "multicalls.h"
	28
a122d623 JF	29	#define MC_DEBUG 1
a122d623 JF	30
d66bf8fc	31	#define MC_BATCH 32
400d3494	32	#define MC_ARGS (MC_BATCH * 16)
5ead97c8 JF	33
	34	struct mc_buffer {
	35	struct multicall_entry entries[MC_BATCH];
a122d623 JF	36	#if MC_DEBUG
	37	struct multicall_entry debug[MC_BATCH];
	38	#endif
400d3494	39	unsigned char args[MC_ARGS];
91e0c5f3 JF	40	struct callback {
	41	void (fn)(void );
	42	void *data;
	43	} callbacks[MC_BATCH];
	44	unsigned mcidx, argidx, cbidx;
5ead97c8 JF	45	};
	46
	47	static DEFINE_PER_CPU(struct mc_buffer, mc_buffer);
	48	DEFINE_PER_CPU(unsigned long, xen_mc_irq_flags);
	49
	50	void xen_mc_flush(void)
	51	{
f120f13e	52	struct mc_buffer *b = &__get_cpu_var(mc_buffer);
5ead97c8 JF	53	int ret = 0;
5ead97c8 JF	54	unsigned long flags;
91e0c5f3	55	int i;
5ead97c8	56
f120f13e JF	57	BUG_ON(preemptible());
f120f13e JF	58
5ead97c8 JF	59	/* Disable interrupts in case someone comes in and queues
	60	something in the middle */
	61	local_irq_save(flags);
	62
	63	if (b->mcidx) {
a122d623 JF	64	#if MC_DEBUG
	65	memcpy(b->debug, b->entries,
	66	b->mcidx * sizeof(struct multicall_entry));
	67	#endif
	68
5ead97c8 JF	69	if (HYPERVISOR_multicall(b->entries, b->mcidx) != 0)
	70	BUG();
	71	for (i = 0; i < b->mcidx; i++)
	72	if (b->entries[i].result < 0)
	73	ret++;
a122d623 JF	74
	75	#if MC_DEBUG
	76	if (ret) {
	77	printk(KERN_ERR "%d multicall(s) failed: cpu %d\n",
	78	ret, smp_processor_id());
7ebed39f	79	for (i = 0; i < b->mcidx; i++) {
a122d623 JF	80	printk(" call %2d/%d: op=%lu arg=[%lx] result=%ld\n",
	81	i+1, b->mcidx,
	82	b->debug[i].op,
	83	b->debug[i].args[0],
	84	b->entries[i].result);
	85	}
	86	}
	87	#endif
	88
5ead97c8 JF	89	b->mcidx = 0;
	90	b->argidx = 0;
	91	} else
	92	BUG_ON(b->argidx != 0);
	93
5ead97c8 JF	94	local_irq_restore(flags);
5ead97c8 JF	95
7ebed39f	96	for (i = 0; i < b->cbidx; i++) {
91e0c5f3 JF	97	struct callback *cb = &b->callbacks[i];
	98
	99	(*cb->fn)(cb->data);
	100	}
	101	b->cbidx = 0;
	102
5ead97c8 JF	103	BUG_ON(ret);
	104	}
	105
	106	struct multicall_space __xen_mc_entry(size_t args)
	107	{
f120f13e	108	struct mc_buffer *b = &__get_cpu_var(mc_buffer);
5ead97c8	109	struct multicall_space ret;
400d3494	110	unsigned argidx = roundup(b->argidx, sizeof(u64));
5ead97c8	111
f120f13e	112	BUG_ON(preemptible());
400d3494	113	BUG_ON(b->argidx > MC_ARGS);
5ead97c8 JF	114
5ead97c8 JF	115	if (b->mcidx == MC_BATCH \|\|
400d3494	116	(argidx + args) > MC_ARGS) {
5ead97c8	117	xen_mc_flush();
400d3494 JF	118	argidx = roundup(b->argidx, sizeof(u64));
400d3494 JF	119	}
5ead97c8 JF	120
	121	ret.mc = &b->entries[b->mcidx];
	122	b->mcidx++;
400d3494 JF	123	ret.args = &b->args[argidx];
	124	b->argidx = argidx + args;
	125
	126	BUG_ON(b->argidx > MC_ARGS);
	127	return ret;
	128	}
	129
	130	struct multicall_space xen_mc_extend_args(unsigned long op, size_t size)
	131	{
	132	struct mc_buffer *b = &__get_cpu_var(mc_buffer);
	133	struct multicall_space ret = { NULL, NULL };
	134
	135	BUG_ON(preemptible());
	136	BUG_ON(b->argidx > MC_ARGS);
	137
	138	if (b->mcidx == 0)
	139	return ret;
	140
	141	if (b->entries[b->mcidx - 1].op != op)
	142	return ret;
	143
	144	if ((b->argidx + size) > MC_ARGS)
	145	return ret;
	146
	147	ret.mc = &b->entries[b->mcidx - 1];
5ead97c8	148	ret.args = &b->args[b->argidx];
400d3494	149	b->argidx += size;
5ead97c8	150
400d3494	151	BUG_ON(b->argidx > MC_ARGS);
5ead97c8 JF	152	return ret;
5ead97c8 JF	153	}
91e0c5f3 JF	154
	155	void xen_mc_callback(void (fn)(void ), void *data)
	156	{
	157	struct mc_buffer *b = &__get_cpu_var(mc_buffer);
	158	struct callback *cb;
	159
	160	if (b->cbidx == MC_BATCH)
	161	xen_mc_flush();
	162
	163	cb = &b->callbacks[b->cbidx++];
	164	cb->fn = fn;
	165	cb->data = data;
	166	}