linux/arch/x86/xen/multicalls.c

// SPDX-License-Identifier: GPL-2.0
/*
 * 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 <[email protected]>, XenSource Inc, 2007
 */
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/debugfs.h>
#include <linux/jump_label.h>
#include <linux/printk.h>

#include <asm/xen/hypercall.h>

#include "xen-ops.h"

#define MC_BATCH …

#define MC_ARGS …


struct mc_buffer { … };

struct mc_debug_data { … };

static DEFINE_PER_CPU(struct mc_buffer, mc_buffer);
static struct mc_debug_data mc_debug_data_early __initdata;
static DEFINE_PER_CPU(struct mc_debug_data *, mc_debug_data) = …;
static struct mc_debug_data __percpu *mc_debug_data_ptr;
DEFINE_PER_CPU(unsigned long, xen_mc_irq_flags);

static struct static_key mc_debug __ro_after_init;
static bool mc_debug_enabled __initdata;

static int __init xen_parse_mc_debug(char *arg)
{ … }
early_param(…);

void mc_percpu_init(unsigned int cpu)
{ … }

static int __init mc_debug_enable(void)
{ … }
early_initcall(mc_debug_enable);

/* Number of parameters of hypercalls used via multicalls. */
static const uint8_t hpcpars[] = …;

static void print_debug_data(struct mc_buffer *b, struct mc_debug_data *mcdb,
			     int idx)
{ … }

void xen_mc_flush(void)
{ … }

struct multicall_space __xen_mc_entry(size_t args)
{ … }

struct multicall_space xen_mc_extend_args(unsigned long op, size_t size)
{ … }

void xen_mc_callback(void (*fn)(void *), void *data)
{ … }