forked from Minki/linux
04ef0f1a01
The problem is that the function 'send_reply_to_slave' gets the 'req_sa_mad' as a pointer whose address is only aliged to 4 bytes but is 8 bytes in size. This can result in unaligned access faults on certain architectures. Sowmini Varadhan pointed to this reply from Dave Miller that say that memcpy should not be used to solve alignment issues: https://lkml.org/lkml/2015/10/21/352 Optimization of memcpy to 'ldx' instruction can only happen if the compiler knows that the size of the data we are copying is 8 bytes and it assumes it is aligned to 8 bytes. If the compiler know the type is not aligned to 8 it must not optimize the 8 byte copy. Defining the data type as aligned to 4 forces the compiler to treat all accesses as though they aren't aligned and avoids the 'ldx' optimization. Full credit for the idea goes to Jason Gunthorpe <jgunthorpe@obsidianresearch.com>. Signed-off-by: Shamir Rabinovitch <shamir.rabinovitch@oracle.com> Signed-off-by: Doug Ledford <dledford@redhat.com> |
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