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Subject[PATCH 04/10] xen: add batch completion callbacks
This adds a mechanism to register a callback function to be called once
a batch of hypercalls has been issued. This is typically used to unlock
things which must remain locked until the hypercall has taken place.

[ Stable folks: pre-req for 2.6.23 bugfix "xen: deal with stale cr3
values when unpinning pagetables" ]

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Stable Kernel <stable@kernel.org>

---
arch/i386/xen/multicalls.c | 29 ++++++++++++++++++++++++++---
arch/i386/xen/multicalls.h | 3 +++
2 files changed, 29 insertions(+), 3 deletions(-)
===================================================================
--- a/arch/i386/xen/multicalls.c
+++ b/arch/i386/xen/multicalls.c
@@ -32,7 +32,11 @@ struct mc_buffer {
struct mc_buffer {
struct multicall_entry entries[MC_BATCH];
u64 args[MC_ARGS];
- unsigned mcidx, argidx;
+ struct callback {
+ void (*fn)(void *);
+ void *data;
+ } callbacks[MC_BATCH];
+ unsigned mcidx, argidx, cbidx;
};

static DEFINE_PER_CPU(struct mc_buffer, mc_buffer);
@@ -43,6 +47,7 @@ void xen_mc_flush(void)
struct mc_buffer *b = &__get_cpu_var(mc_buffer);
int ret = 0;
unsigned long flags;
+ int i;

BUG_ON(preemptible());

@@ -51,8 +56,6 @@ void xen_mc_flush(void)
local_irq_save(flags);

if (b->mcidx) {
- int i;
-
if (HYPERVISOR_multicall(b->entries, b->mcidx) != 0)
BUG();
for (i = 0; i < b->mcidx; i++)
@@ -64,6 +67,13 @@ void xen_mc_flush(void)
BUG_ON(b->argidx != 0);

local_irq_restore(flags);
+
+ for(i = 0; i < b->cbidx; i++) {
+ struct callback *cb = &b->callbacks[i];
+
+ (*cb->fn)(cb->data);
+ }
+ b->cbidx = 0;

BUG_ON(ret);
}
@@ -88,3 +98,16 @@ struct multicall_space __xen_mc_entry(si

return ret;
}
+
+void xen_mc_callback(void (*fn)(void *), void *data)
+{
+ struct mc_buffer *b = &__get_cpu_var(mc_buffer);
+ struct callback *cb;
+
+ if (b->cbidx == MC_BATCH)
+ xen_mc_flush();
+
+ cb = &b->callbacks[b->cbidx++];
+ cb->fn = fn;
+ cb->data = data;
+}
===================================================================
--- a/arch/i386/xen/multicalls.h
+++ b/arch/i386/xen/multicalls.h
@@ -42,4 +42,7 @@ static inline void xen_mc_issue(unsigned
local_irq_restore(x86_read_percpu(xen_mc_irq_flags));
}

+/* Set up a callback to be called when the current batch is flushed */
+void xen_mc_callback(void (*fn)(void *), void *data);
+
#endif /* _XEN_MULTICALLS_H */
--

-
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