forked from Minki/linux
d66bf8fcf3
This patch uses the lazy-mmu hooks to batch mmu operations where possible. This is primarily useful for batching operations applied to active pagetables, which happens during mprotect, munmap, mremap and the like (mmap does not do bulk pagetable operations, so it isn't helped). Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Acked-by: Chris Wright <chrisw@sous-sol.org>
91 lines
2.3 KiB
C
91 lines
2.3 KiB
C
/*
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* Xen hypercall batching.
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*
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* Xen allows multiple hypercalls to be issued at once, using the
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* multicall interface. This allows the cost of trapping into the
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* hypervisor to be amortized over several calls.
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*
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* This file implements a simple interface for multicalls. There's a
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* per-cpu buffer of outstanding multicalls. When you want to queue a
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* multicall for issuing, you can allocate a multicall slot for the
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* call and its arguments, along with storage for space which is
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* pointed to by the arguments (for passing pointers to structures,
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* etc). When the multicall is actually issued, all the space for the
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* commands and allocated memory is freed for reuse.
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*
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* Multicalls are flushed whenever any of the buffers get full, or
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* when explicitly requested. There's no way to get per-multicall
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* return results back. It will BUG if any of the multicalls fail.
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*
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* Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
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*/
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#include <linux/percpu.h>
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#include <linux/hardirq.h>
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#include <asm/xen/hypercall.h>
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#include "multicalls.h"
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#define MC_BATCH 32
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#define MC_ARGS (MC_BATCH * 16 / sizeof(u64))
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struct mc_buffer {
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struct multicall_entry entries[MC_BATCH];
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u64 args[MC_ARGS];
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unsigned mcidx, argidx;
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};
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static DEFINE_PER_CPU(struct mc_buffer, mc_buffer);
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DEFINE_PER_CPU(unsigned long, xen_mc_irq_flags);
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void xen_mc_flush(void)
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{
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struct mc_buffer *b = &__get_cpu_var(mc_buffer);
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int ret = 0;
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unsigned long flags;
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BUG_ON(preemptible());
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/* Disable interrupts in case someone comes in and queues
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something in the middle */
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local_irq_save(flags);
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if (b->mcidx) {
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int i;
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if (HYPERVISOR_multicall(b->entries, b->mcidx) != 0)
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BUG();
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for (i = 0; i < b->mcidx; i++)
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if (b->entries[i].result < 0)
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ret++;
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b->mcidx = 0;
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b->argidx = 0;
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} else
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BUG_ON(b->argidx != 0);
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local_irq_restore(flags);
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BUG_ON(ret);
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}
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struct multicall_space __xen_mc_entry(size_t args)
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{
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struct mc_buffer *b = &__get_cpu_var(mc_buffer);
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struct multicall_space ret;
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unsigned argspace = (args + sizeof(u64) - 1) / sizeof(u64);
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BUG_ON(preemptible());
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BUG_ON(argspace > MC_ARGS);
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if (b->mcidx == MC_BATCH ||
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(b->argidx + argspace) > MC_ARGS)
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xen_mc_flush();
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ret.mc = &b->entries[b->mcidx];
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b->mcidx++;
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ret.args = &b->args[b->argidx];
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b->argidx += argspace;
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return ret;
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}
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