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| author |   Jeremy Fitzhardinge <jeremy@goop.org> | 2008-06-16 04:30:02 -0700 |
|---|---|---|
| committer |   Ingo Molnar <mingo@elte.hu> | 2008-06-25 15:17:23 +0200 |
| commit | e57778a1e30470c9f5b79e370511b9af29b59c48 (patch) | |
| tree | 01239f16b016d57206ba8bdfcbd443d8a26cd5e4 /include/xen/interface/features.h | |
| parent | paravirt: add hooks for ptep_modify_prot_start/commit (diff) | |
| download | linux-dev-e57778a1e30470c9f5b79e370511b9af29b59c48.tar.xz linux-dev-e57778a1e30470c9f5b79e370511b9af29b59c48.zip | |
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/features.h')
| -rw-r--r-- | include/xen/interface/features.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/xen/interface/features.h b/include/xen/interface/features.h index d73228d16488..f51b6413b054 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 + #define XENFEAT_NR_SUBMAPS 1 #endif /* __XEN_PUBLIC_FEATURES_H__ */ |