diff options
Diffstat (limited to 'include/exec/memop.h')
| -rw-r--r-- | include/exec/memop.h | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/include/exec/memop.h b/include/exec/memop.h index 07f5f88188..a86dc6743a 100644 --- a/include/exec/memop.h +++ b/include/exec/memop.h @@ -72,6 +72,43 @@ typedef enum MemOp { MO_ALIGN_64 = 6 << MO_ASHIFT, MO_ALIGN = MO_AMASK, + /* + * MO_ATOM_* describes the atomicity requirements of the operation: + * MO_ATOM_IFALIGN: the operation must be single-copy atomic if it + * is aligned; if unaligned there is no atomicity. + * MO_ATOM_IFALIGN_PAIR: the entire operation may be considered to + * be a pair of half-sized operations which are packed together + * for convenience, with single-copy atomicity on each half if + * the half is aligned. + * This is the atomicity e.g. of Arm pre-FEAT_LSE2 LDP. + * MO_ATOM_WITHIN16: the operation is single-copy atomic, even if it + * is unaligned, so long as it does not cross a 16-byte boundary; + * if it crosses a 16-byte boundary there is no atomicity. + * This is the atomicity e.g. of Arm FEAT_LSE2 LDR. + * MO_ATOM_WITHIN16_PAIR: the entire operation is single-copy atomic, + * if it happens to be within a 16-byte boundary, otherwise it + * devolves to a pair of half-sized MO_ATOM_WITHIN16 operations. + * Depending on alignment, one or both will be single-copy atomic. + * This is the atomicity e.g. of Arm FEAT_LSE2 LDP. + * MO_ATOM_SUBALIGN: the operation is single-copy atomic by parts + * by the alignment. E.g. if the address is 0 mod 4, then each + * 4-byte subobject is single-copy atomic. + * This is the atomicity e.g. of IBM Power. + * MO_ATOM_NONE: the operation has no atomicity requirements. + * + * Note the default (i.e. 0) value is single-copy atomic to the + * size of the operation, if aligned. This retains the behaviour + * from before this field was introduced. + */ + MO_ATOM_SHIFT = 8, + MO_ATOM_IFALIGN = 0 << MO_ATOM_SHIFT, + MO_ATOM_IFALIGN_PAIR = 1 << MO_ATOM_SHIFT, + MO_ATOM_WITHIN16 = 2 << MO_ATOM_SHIFT, + MO_ATOM_WITHIN16_PAIR = 3 << MO_ATOM_SHIFT, + MO_ATOM_SUBALIGN = 4 << MO_ATOM_SHIFT, + MO_ATOM_NONE = 5 << MO_ATOM_SHIFT, + MO_ATOM_MASK = 7 << MO_ATOM_SHIFT, + /* Combinations of the above, for ease of use. */ MO_UB = MO_8, MO_UW = MO_16, |