diff options
Diffstat (limited to 'arch/i386/xen/multicalls.c')
-rw-r--r-- | arch/i386/xen/multicalls.c | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/arch/i386/xen/multicalls.c b/arch/i386/xen/multicalls.c new file mode 100644 index 000000000000..c837e8e463db --- /dev/null +++ b/arch/i386/xen/multicalls.c | |||
@@ -0,0 +1,90 @@ | |||
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> | ||
23 | #include <linux/hardirq.h> | ||
24 | |||
25 | #include <asm/xen/hypercall.h> | ||
26 | |||
27 | #include "multicalls.h" | ||
28 | |||
29 | #define MC_BATCH 32 | ||
30 | #define MC_ARGS (MC_BATCH * 16 / 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 | { | ||
43 | struct mc_buffer *b = &__get_cpu_var(mc_buffer); | ||
44 | int ret = 0; | ||
45 | unsigned long flags; | ||
46 | |||
47 | BUG_ON(preemptible()); | ||
48 | |||
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 | |||
66 | local_irq_restore(flags); | ||
67 | |||
68 | BUG_ON(ret); | ||
69 | } | ||
70 | |||
71 | struct multicall_space __xen_mc_entry(size_t args) | ||
72 | { | ||
73 | struct mc_buffer *b = &__get_cpu_var(mc_buffer); | ||
74 | struct multicall_space ret; | ||
75 | unsigned argspace = (args + sizeof(u64) - 1) / sizeof(u64); | ||
76 | |||
77 | BUG_ON(preemptible()); | ||
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 | |||
89 | return ret; | ||
90 | } | ||