path: root/arch/x86/xen/multicalls.h
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authorJeremy Fitzhardinge <jeremy@goop.org>2008-06-16 04:30:03 -0700
committerIngo Molnar <mingo@elte.hu>2008-06-25 15:17:34 +0200
commit400d34944c4ad82a817c06e570bc93b1114aa596 (patch)
treed963075e7a293c8481adcc66aff0fa5d87f35c09 /arch/x86/xen/multicalls.h
parente57778a1e30470c9f5b79e370511b9af29b59c48 (diff)
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>
Diffstat (limited to 'arch/x86/xen/multicalls.h')
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/x86/xen/multicalls.h b/arch/x86/xen/multicalls.h
index 8bae996d99a..85893824161 100644
--- a/arch/x86/xen/multicalls.h
+++ b/arch/x86/xen/multicalls.h
@@ -45,4 +45,16 @@ static inline void xen_mc_issue(unsigned mode)
/* Set up a callback to be called when the current batch is flushed */
void xen_mc_callback(void (*fn)(void *), void *data);
+ * Try to extend the arguments of the previous multicall command. The
+ * previous command's op must match. If it does, then it attempts to
+ * extend the argument space allocated to the multicall entry by
+ * arg_size bytes.
+ *
+ * The returned multicall_space will return with mc pointing to the
+ * command on success, or NULL on failure, and args pointing to the
+ * newly allocated space.
+ */
+struct multicall_space xen_mc_extend_args(unsigned long op, size_t arg_size);
#endif /* _XEN_MULTICALLS_H */