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| author | Linus Walleij <[email protected]> | 2015-12-21 08:36:21 +0000 |
|---|---|---|
| committer | Linus Walleij <[email protected]> | 2015-12-21 08:36:21 +0000 |
| commit | 0529357f102b96f68bc199f858d1c3b07f4b674c (patch) | |
| tree | eaa047952a768099e00a5245afa0d84799df6990 /include/xen/interface/io/ring.h | |
| parent | gpio: pch: fix non-DT build (diff) | |
| parent | Linux 4.4-rc6 (diff) | |
| download | kernel-0529357f102b96f68bc199f858d1c3b07f4b674c.tar.gz kernel-0529357f102b96f68bc199f858d1c3b07f4b674c.zip | |
Merge tag 'v4.4-rc6' into devel
Linux 4.4-rc6
Diffstat (limited to 'include/xen/interface/io/ring.h')
| -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 7d28aff605c7..7dc685b4057d 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)) |