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| author | André Fabian Silva Delgado <emulatorman@parabola.nu> | 2016-01-20 14:01:31 -0300 |
|---|---|---|
| committer | André Fabian Silva Delgado <emulatorman@parabola.nu> | 2016-01-20 14:01:31 -0300 |
| commit | b4b7ff4b08e691656c9d77c758fc355833128ac0 (patch) | |
| tree | 82fcb00e6b918026dc9f2d1f05ed8eee83874cc0 /include/xen/interface/io | |
| parent | 35acfa0fc609f2a2cd95cef4a6a9c3a5c38f1778 (diff) | |
Linux-libre 4.4-gnupck-4.4-gnu
Diffstat (limited to 'include/xen/interface/io')
| -rw-r--r-- | include/xen/interface/io/ring.h | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/include/xen/interface/io/ring.h b/include/xen/interface/io/ring.h index 7d28aff60..7dc685b40 100644 --- a/include/xen/interface/io/ring.h +++ b/include/xen/interface/io/ring.h @@ -181,6 +181,20 @@ struct __name##_back_ring { \ #define RING_GET_REQUEST(_r, _idx) \ (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req)) +/* + * Get a local copy of a request. + * + * Use this in preference to RING_GET_REQUEST() so all processing is + * done on a local copy that cannot be modified by the other end. + * + * Note that https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 may cause this + * to be ineffective where _req is a struct which consists of only bitfields. + */ +#define RING_COPY_REQUEST(_r, _idx, _req) do { \ + /* Use volatile to force the copy into _req. */ \ + *(_req) = *(volatile typeof(_req))RING_GET_REQUEST(_r, _idx); \ +} while (0) + #define RING_GET_RESPONSE(_r, _idx) \ (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp)) |