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 | ||
29 | #define MC_BATCH 8 | |
30 | #define MC_ARGS (MC_BATCH * 32 / sizeof(u64)) | |
31 | ||
32 | struct mc_buffer { | |
33 | struct multicall_entry entries[MC_BATCH]; | |
34 | u64 args[MC_ARGS]; | |
35 | unsigned mcidx, argidx; | |
36 | }; | |
37 | ||
38 | static DEFINE_PER_CPU(struct mc_buffer, mc_buffer); | |
39 | DEFINE_PER_CPU(unsigned long, xen_mc_irq_flags); | |
40 | ||
41 | void xen_mc_flush(void) | |
42 | { | |
f120f13e | 43 | struct mc_buffer *b = &__get_cpu_var(mc_buffer); |
5ead97c8 JF |
44 | int ret = 0; |
45 | unsigned long flags; | |
46 | ||
f120f13e JF |
47 | BUG_ON(preemptible()); |
48 | ||
5ead97c8 JF |
49 | /* Disable interrupts in case someone comes in and queues |
50 | something in the middle */ | |
51 | local_irq_save(flags); | |
52 | ||
53 | if (b->mcidx) { | |
54 | int i; | |
55 | ||
56 | if (HYPERVISOR_multicall(b->entries, b->mcidx) != 0) | |
57 | BUG(); | |
58 | for (i = 0; i < b->mcidx; i++) | |
59 | if (b->entries[i].result < 0) | |
60 | ret++; | |
61 | b->mcidx = 0; | |
62 | b->argidx = 0; | |
63 | } else | |
64 | BUG_ON(b->argidx != 0); | |
65 | ||
5ead97c8 JF |
66 | local_irq_restore(flags); |
67 | ||
68 | BUG_ON(ret); | |
69 | } | |
70 | ||
71 | struct multicall_space __xen_mc_entry(size_t args) | |
72 | { | |
f120f13e | 73 | struct mc_buffer *b = &__get_cpu_var(mc_buffer); |
5ead97c8 JF |
74 | struct multicall_space ret; |
75 | unsigned argspace = (args + sizeof(u64) - 1) / sizeof(u64); | |
76 | ||
f120f13e | 77 | BUG_ON(preemptible()); |
5ead97c8 JF |
78 | BUG_ON(argspace > MC_ARGS); |
79 | ||
80 | if (b->mcidx == MC_BATCH || | |
81 | (b->argidx + argspace) > MC_ARGS) | |
82 | xen_mc_flush(); | |
83 | ||
84 | ret.mc = &b->entries[b->mcidx]; | |
85 | b->mcidx++; | |
86 | ret.args = &b->args[b->argidx]; | |
87 | b->argidx += argspace; | |
88 | ||
5ead97c8 JF |
89 | return ret; |
90 | } |