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xen: add mechanism to extend existing multicalls

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Some Xen hypercalls accept an array of operations to work on.  In
general this is because its more efficient for the hypercall to the
work all at once rather than as separate hypercalls (even batched as a
multicall).

This patch adds a mechanism (xen_mc_extend_args()) to allocate more
argument space to the last-issued multicall, in order to extend its
argument list.

The user of this mechanism is xen/mmu.c, which uses it to extend the
args array of mmu_update.  This is particularly valuable when doing
the update for a large mprotect, which goes via
ptep_modify_prot_commit(), but it also manages to batch updates to
pgd/pmds as well.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jeremy Fitzhardinge
2008-06-16 04:30:03 -07:00
committed by Ingo Molnar
parent e57778a1e3
commit 400d34944c
3 changed files with 82 additions and 27 deletions
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42
arch/x86/xen/multicalls.c
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@@ -29,14 +29,14 @@
#define MC_DEBUG 1
#define MC_BATCH 32
#define MC_ARGS (MC_BATCH * 16 / sizeof(u64))
#define MC_ARGS (MC_BATCH * 16)
struct mc_buffer {
struct multicall_entry entries[MC_BATCH];
#if MC_DEBUG
struct multicall_entry debug[MC_BATCH];
#endif
u64 args[MC_ARGS];
unsigned char args[MC_ARGS];
struct callback {
void (*fn)(void *);
void *data;
@@ -107,20 +107,48 @@ struct multicall_space __xen_mc_entry(size_t args)
{
struct mc_buffer *b = &__get_cpu_var(mc_buffer);
struct multicall_space ret;
unsigned argspace = (args + sizeof(u64) - 1) / sizeof(u64);
unsigned argidx = roundup(b->argidx, sizeof(u64));
BUG_ON(preemptible());
BUG_ON(argspace > MC_ARGS);
BUG_ON(b->argidx > MC_ARGS);
if (b->mcidx == MC_BATCH ||
(b->argidx + argspace) > MC_ARGS)
(argidx + args) > MC_ARGS) {
xen_mc_flush();
argidx = roundup(b->argidx, sizeof(u64));
}
ret.mc = &b->entries[b->mcidx];
b->mcidx++;
ret.args = &b->args[b->argidx];
b->argidx += argspace;
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 = &__get_cpu_var(mc_buffer);
struct multicall_space ret = { NULL, NULL };
BUG_ON(preemptible());
BUG_ON(b->argidx > MC_ARGS);
if (b->mcidx == 0)
return ret;
if (b->entries[b->mcidx - 1].op != op)
return ret;
if ((b->argidx + size) > MC_ARGS)
return ret;
ret.mc = &b->entries[b->mcidx - 1];
ret.args = &b->args[b->argidx];
b->argidx += size;
BUG_ON(b->argidx > MC_ARGS);
return ret;
}