--- /dev/null
+/*
+ * 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 = privcmd_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;
+}
Code Review / kvmfornfv.git / blobdiff