From: Toshi Kani Date: Thu, 11 Feb 2016 21:24:17 +0000 (-0700) Subject: x86/uaccess/64: Handle the caching of 4-byte nocache copies properly in __copy_user_n... X-Git-Tag: v3.2.79~39 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=256cf9c45cad4da99771b42835fa37f0e7b19629;p=pandora-kernel.git x86/uaccess/64: Handle the caching of 4-byte nocache copies properly in __copy_user_nocache() commit a82eee7424525e34e98d821dd059ce14560a1e35 upstream. Data corruption issues were observed in tests which initiated a system crash/reset while accessing BTT devices. This problem is reproducible. The BTT driver calls pmem_rw_bytes() to update data in pmem devices. This interface calls __copy_user_nocache(), which uses non-temporal stores so that the stores to pmem are persistent. __copy_user_nocache() uses non-temporal stores when a request size is 8 bytes or larger (and is aligned by 8 bytes). The BTT driver updates the BTT map table, which entry size is 4 bytes. Therefore, updates to the map table entries remain cached, and are not written to pmem after a crash. Change __copy_user_nocache() to use non-temporal store when a request size is 4 bytes. The change extends the current byte-copy path for a less-than-8-bytes request, and does not add any overhead to the regular path. Reported-and-tested-by: Micah Parrish Reported-and-tested-by: Brian Boylston Signed-off-by: Toshi Kani Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Borislav Petkov Cc: Brian Gerst Cc: Dan Williams Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Peter Zijlstra Cc: Ross Zwisler Cc: Thomas Gleixner Cc: Toshi Kani Cc: Vishal Verma Cc: linux-nvdimm@lists.01.org Link: http://lkml.kernel.org/r/1455225857-12039-3-git-send-email-toshi.kani@hpe.com [ Small readability edits. ] Signed-off-by: Ingo Molnar [bwh: Backported to 3.2: aadjust filename, context] Signed-off-by: Ben Hutchings --- Reading git-diff-tree failed