1 files changed, 299 insertions, 0 deletions
diff --git a/arch/x86/xen/multicalls.c b/arch/x86/xen/multicalls.c
new file mode 100644
index 000000000..7237d56a9
--- /dev/null
+++ b/arch/x86/xen/multicalls.c
@@ -0,0 +1,299 @@
+// 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 <jeremy@xensource.com>, 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	32
+
+#define MC_ARGS		(MC_BATCH * 16)
+
+
+struct mc_buffer {
+	unsigned mcidx, argidx, cbidx;
+	struct multicall_entry entries[MC_BATCH];
+	unsigned char args[MC_ARGS];
+	struct callback {
+		void (*fn)(void *);
+		void *data;
+	} callbacks[MC_BATCH];
+};
+
+struct mc_debug_data {
+	struct multicall_entry entries[MC_BATCH];
+	void *caller[MC_BATCH];
+	size_t argsz[MC_BATCH];
+	unsigned long *args[MC_BATCH];
+};
+
+static DEFINE_PER_CPU(struct mc_buffer, mc_buffer);
+static struct mc_debug_data mc_debug_data_early __initdata;
+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 struct mc_debug_data * __ref get_mc_debug(void)
+{
+	if (!mc_debug_data_ptr)
+		return &mc_debug_data_early;
+
+	return this_cpu_ptr(mc_debug_data_ptr);
+}
+
+static int __init xen_parse_mc_debug(char *arg)
+{
+	mc_debug_enabled = true;
+	static_key_slow_inc(&mc_debug);
+
+	return 0;
+}
+early_param("xen_mc_debug", xen_parse_mc_debug);
+
+static int __init mc_debug_enable(void)
+{
+	unsigned long flags;
+	struct mc_debug_data __percpu *mcdb;
+
+	if (!mc_debug_enabled)
+		return 0;
+
+	mcdb = alloc_percpu(struct mc_debug_data);
+	if (!mcdb) {
+		pr_err("xen_mc_debug inactive\n");
+		static_key_slow_dec(&mc_debug);
+		return -ENOMEM;
+	}
+
+	/* Be careful when switching to percpu debug data. */
+	local_irq_save(flags);
+	xen_mc_flush();
+	mc_debug_data_ptr = mcdb;
+	local_irq_restore(flags);
+
+	pr_info("xen_mc_debug active\n");
+
+	return 0;
+}
+early_initcall(mc_debug_enable);
+
+/* Number of parameters of hypercalls used via multicalls. */
+static const uint8_t hpcpars[] = {
+	[__HYPERVISOR_mmu_update] = 4,
+	[__HYPERVISOR_stack_switch] = 2,
+	[__HYPERVISOR_fpu_taskswitch] = 1,
+	[__HYPERVISOR_update_descriptor] = 2,
+	[__HYPERVISOR_update_va_mapping] = 3,
+	[__HYPERVISOR_mmuext_op] = 4,
+};
+
+static void print_debug_data(struct mc_buffer *b, struct mc_debug_data *mcdb,
+			     int idx)
+{
+	unsigned int arg;
+	unsigned int opidx = mcdb->entries[idx].op & 0xff;
+	unsigned int pars = 0;
+
+	pr_err("  call %2d: op=%lu result=%ld caller=%pS ", idx + 1,
+	       mcdb->entries[idx].op, b->entries[idx].result,
+	       mcdb->caller[idx]);
+	if (opidx < ARRAY_SIZE(hpcpars))
+		pars = hpcpars[opidx];
+	if (pars) {
+		pr_cont("pars=");
+		for (arg = 0; arg < pars; arg++)
+			pr_cont("%lx ", mcdb->entries[idx].args[arg]);
+	}
+	if (mcdb->argsz[idx]) {
+		pr_cont("args=");
+		for (arg = 0; arg < mcdb->argsz[idx] / 8; arg++)
+			pr_cont("%lx ", mcdb->args[idx][arg]);
+	}
+	pr_cont("\n");
+}
+
+void xen_mc_flush(void)
+{
+	struct mc_buffer *b = this_cpu_ptr(&mc_buffer);
+	struct multicall_entry *mc;
+	struct mc_debug_data *mcdb = NULL;
+	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);
+
+	trace_xen_mc_flush(b->mcidx, b->argidx, b->cbidx);
+
+	if (static_key_false(&mc_debug)) {
+		mcdb = get_mc_debug();
+		memcpy(mcdb->entries, b->entries,
+		       b->mcidx * sizeof(struct multicall_entry));
+	}
+
+	switch (b->mcidx) {
+	case 0:
+		/* no-op */
+		BUG_ON(b->argidx != 0);
+		break;
+
+	case 1:
+		/* Singleton multicall - bypass multicall machinery
+		   and just do the call directly. */
+		mc = &b->entries[0];
+
+		mc->result = xen_single_call(mc->op, mc->args[0], mc->args[1],
+					     mc->args[2], mc->args[3],
+					     mc->args[4]);
+		ret = mc->result < 0;
+		break;
+
+	default:
+		if (HYPERVISOR_multicall(b->entries, b->mcidx) != 0)
+			BUG();
+		for (i = 0; i < b->mcidx; i++)
+			if (b->entries[i].result < 0)
+				ret++;
+	}
+
+	if (WARN_ON(ret)) {
+		pr_err("%d of %d multicall(s) failed: cpu %d\n",
+		       ret, b->mcidx, smp_processor_id());
+		for (i = 0; i < b->mcidx; i++) {
+			if (static_key_false(&mc_debug)) {
+				print_debug_data(b, mcdb, i);
+			} else if (b->entries[i].result < 0) {
+				pr_err("  call %2d: op=%lu arg=[%lx] result=%ld\n",
+				       i + 1,
+				       b->entries[i].op,
+				       b->entries[i].args[0],
+				       b->entries[i].result);
+			}
+		}
+	}
+
+	b->mcidx = 0;
+	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);
+}
+
+struct multicall_space __xen_mc_entry(size_t args)
+{
+	struct mc_buffer *b = this_cpu_ptr(&mc_buffer);
+	struct multicall_space ret;
+	unsigned argidx = roundup(b->argidx, sizeof(u64));
+
+	trace_xen_mc_entry_alloc(args);
+
+	BUG_ON(preemptible());
+	BUG_ON(b->argidx >= MC_ARGS);
+
+	if (unlikely(b->mcidx == MC_BATCH ||
+		     (argidx + args) >= MC_ARGS)) {
+		trace_xen_mc_flush_reason((b->mcidx == MC_BATCH) ?
+					  XEN_MC_FL_BATCH : XEN_MC_FL_ARGS);
+		xen_mc_flush();
+		argidx = roundup(b->argidx, sizeof(u64));
+	}
+
+	ret.mc = &b->entries[b->mcidx];
+	if (static_key_false(&mc_debug)) {
+		struct mc_debug_data *mcdb = get_mc_debug();
+
+		mcdb->caller[b->mcidx] = __builtin_return_address(0);
+		mcdb->argsz[b->mcidx] = args;
+		mcdb->args[b->mcidx] = (unsigned long *)(&b->args[argidx]);
+	}
+	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 = this_cpu_ptr(&mc_buffer);
+	struct multicall_space ret = { NULL, NULL };
+
+	BUG_ON(preemptible());
+	BUG_ON(b->argidx >= MC_ARGS);
+
+	if (unlikely(b->mcidx == 0 ||
+		     b->entries[b->mcidx - 1].op != op)) {
+		trace_xen_mc_extend_args(op, size, XEN_MC_XE_BAD_OP);
+		goto out;
+	}
+
+	if (unlikely((b->argidx + size) >= MC_ARGS)) {
+		trace_xen_mc_extend_args(op, size, XEN_MC_XE_NO_SPACE);
+		goto out;
+	}
+
+	ret.mc = &b->entries[b->mcidx - 1];
+	ret.args = &b->args[b->argidx];
+	b->argidx += size;
+
+	BUG_ON(b->argidx >= MC_ARGS);
+
+	trace_xen_mc_extend_args(op, size, XEN_MC_XE_OK);
+out:
+	return ret;
+}
+
+void xen_mc_callback(void (*fn)(void *), void *data)
+{
+	struct mc_buffer *b = this_cpu_ptr(&mc_buffer);
+	struct callback *cb;
+
+	if (b->cbidx == MC_BATCH) {
+		trace_xen_mc_flush_reason(XEN_MC_FL_CALLBACK);
+		xen_mc_flush();
+	}
+
+	trace_xen_mc_callback(fn, data);
+
+	cb = &b->callbacks[b->cbidx++];
+	cb->fn = fn;
+	cb->data = data;
+}