path: root/include/xen/interface
diff options
authorJeremy Fitzhardinge <jeremy@goop.org>2008-06-16 04:30:02 -0700
committerIngo Molnar <mingo@elte.hu>2008-06-25 15:17:23 +0200
commite57778a1e30470c9f5b79e370511b9af29b59c48 (patch)
tree01239f16b016d57206ba8bdfcbd443d8a26cd5e4 /include/xen/interface
parent08b882c627aeeeb3cfd3c4354f0d360d7949549d (diff)
xen: implement ptep_modify_prot_start/commit
Xen has a pte update function which will update a pte while preserving its accessed and dirty bits. This means that ptep_modify_prot_start() can be implemented as a simple read of the pte value. The hardware may update the pte in the meantime, but ptep_modify_prot_commit() updates it while preserving any changes that may have happened in the meantime. The updates in ptep_modify_prot_commit() are batched if we're currently in lazy mmu mode. The mmu_update hypercall can take a batch of updates to perform, but this code doesn't make particular use of that feature, in favour of using generic multicall batching to get them all into the hypervisor. The net effect of this is that each mprotect pte update turns from two expensive trap-and-emulate faults into they hypervisor into a single hypercall whose cost is amortized in a batched multicall. 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 'include/xen/interface')
2 files changed, 10 insertions, 2 deletions
diff --git a/include/xen/interface/features.h b/include/xen/interface/features.h
index d73228d1648..f51b6413b05 100644
--- a/include/xen/interface/features.h
+++ b/include/xen/interface/features.h
@@ -38,6 +38,9 @@
#define XENFEAT_pae_pgdir_above_4gb 4
+/* x86: Does this Xen host support the MMU_PT_UPDATE_PRESERVE_AD hypercall? */
+#define XENFEAT_mmu_pt_update_preserve_ad 5
#endif /* __XEN_PUBLIC_FEATURES_H__ */
diff --git a/include/xen/interface/xen.h b/include/xen/interface/xen.h
index 819a0331cda..2befa3e2f1b 100644
--- a/include/xen/interface/xen.h
+++ b/include/xen/interface/xen.h
@@ -114,9 +114,14 @@
* ptr[:2] -- Machine address within the frame whose mapping to modify.
* The frame must belong to the FD, if one is specified.
* val -- Value to write into the mapping entry.
+ *
+ * ptr[1:0] == MMU_PT_UPDATE_PRESERVE_AD:
+ * As MMU_NORMAL_PT_UPDATE above, but A/D bits currently in the PTE are ORed
+ * with those in @val.
-#define MMU_NORMAL_PT_UPDATE 0 /* checked '*ptr = val'. ptr is MA. */
-#define MMU_MACHPHYS_UPDATE 1 /* ptr = MA of frame to modify entry for */
+#define MMU_NORMAL_PT_UPDATE 0 /* checked '*ptr = val'. ptr is MA. */
+#define MMU_MACHPHYS_UPDATE 1 /* ptr = MA of frame to modify entry for */
+#define MMU_PT_UPDATE_PRESERVE_AD 2 /* atomically: *ptr = val | (*ptr&(A|D)) */