From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Toshi Kani Subject: [PATCH 0/2] Fix BTT data corruptions after crash Date: Thu, 28 Jan 2016 11:12:48 -0700 Message-Id: <1454004770-6318-1-git-send-email-toshi.kani@hpe.com> Sender: linux-kernel-owner@vger.kernel.org To: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, bp@suse.de, dan.j.williams@intel.com Cc: ross.zwisler@linux.intel.com, vishal.l.verma@intel.com, micah.parrish@hpe.com, brian.boylston@hpe.com, x86@kernel.org, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org List-ID: 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. Since the BTT driver makes previous blocks free and uses them for subsequent writes, the map table ends up pointing to blocks allocated for other LBAs after a crash. Patch 1 extends __copy_user_nocache() to use non-temporal store for 4 byte copy. This patch fixes the BTT data corruption issue. Patch 2 changes arch_memcpy_to_pmem() to flush processor caches when a request is not naturally aligned or is less than 4 bytes. This is defensive change. --- Toshi Kani (2): 1/2 x86/lib/copy_user_64.S: Handle 4-byte uncached copy 2/2 pmem: Flush cache on unaligned request --- arch/x86/include/asm/pmem.h | 11 +++++++++++ arch/x86/lib/copy_user_64.S | 44 +++++++++++++++++++++++++++++++++----------- 2 files changed, 44 insertions(+), 11 deletions(-)