Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 209 insertions, 0 deletions

diff --git a/arch/x86/xen/multicalls.c b/arch/x86/xen/multicalls.c
new file mode 100644
index 000000000..2bce7958c
--- /dev/null
+++ b/arch/x86/xen/multicalls.c
@@ -0,0 +1,209 @@
+// 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 <asm/xen/hypercall.h>
+
+#include "multicalls.h"
+#include "debugfs.h"
+
+#define MC_BATCH	32
+
+#define MC_DEBUG	0
+
+#define MC_ARGS		(MC_BATCH * 16)
+
+
+struct mc_buffer {
+	unsigned mcidx, argidx, cbidx;
+	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];
+};
+
+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 = this_cpu_ptr(&mc_buffer);
+	struct multicall_entry *mc;
+	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);
+
+	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 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;
+
+	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 = 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 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 = 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;
+}