xen: add mechanism to extend existing multicalls
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>
diff --git a/arch/x86/xen/multicalls.c b/arch/x86/xen/multicalls.c
index 5791eb2..3c63c4d 100644
--- a/arch/x86/xen/multicalls.c
+++ b/arch/x86/xen/multicalls.c
@@ -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 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;
}