** Description changed: - == Comment: #0 - Waiki Wright <wa...@us.ibm.com> - 2020-11-02 17:00:07 - == + SRU Justification: - ---Problem Description--- + [Impact] - A data integrity issue was observed with the Ubuntu 20.04 - 5.4.0-52 and - 20.10 - 5.8.0-26 kernel on Power 9. The root cause is found in the - compiling of p9_hmi_special_emu(). When doing a VMX store (in - __get_user_atomic_128_aligned()) to a buffer (vbuf), the buffer is not - 128 bit aligned. + * A data integrity issue was observed on POWER 9 (DD2.1) systems. - The fixes of this bug are accepted upstream: - 1. - https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?h=fixes&id=1da4a0272c5469169f78cd76cf175ff984f52f06 - ("powerpc: Fix undetected data corruption with P9N DD2.1 VSX CI load emulation") - 2. - https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?h=fixes&id=d1781f23704707d350b8c9006e2bdf5394bf91b2 - ("selftests/powerpc: Make alignment handler test P9N DD2.1 vector CI load workaround") + * It affects Ubuntu 20.04 with kernel 5.4.0-52 and Ubuntu 20.10 with + kernel 5.8.0-26 kernel. + + * The root cause is found in the compiling of p9_hmi_special_emu(). + + * When doing a VMX store (in __get_user_atomic_128_aligned()) to a + buffer (vbuf), the buffer is not 128 bit aligned. + + [Fix] + + * 1da4a0272c54 "powerpc: Fix undetected data corruption with P9N DD2.1 + VSX CI load emulation" + + * d1781f237047 "selftests/powerpc: Make alignment handler test P9N DD2.1 + vector CI load workaround" + + [Test Case] + + * A POWER 9 (DD2.1) bare metal system is needed that has either Ubuntu + 20.04, 20.10 or 21.04 installed. + + * It's best to test this based on a sample application and test case + "selftests/powerpc: Make alignment handler test P9N DD2.1 vector CI load workaround" + + [Regression Potential] + + * The regression risk is relatively moderate, because: + + * it only happens with special VSX (vector) instructions in use, e.g. in + p9_hmi_special_emu + + * it happens on bare metal only and only on POWER 9 (DD2.1) + + * and the changes are very overseeable (in total one effective code line + per patch/commit) + + * Since only p9_hmi_special_emu is touched, this will break in case of + any regressions, but this is already broken based on this bug. + + [Other] + + * According to the reporter this affects Ubuntu 20.04 / 5.4.0-52 and + 20.10 / 5.8.0-26. + + * Since the development of Hirsute is already open the SRU is requested + for Hirsute, too. + + * Patches got upstream accepted in v5.10-rc1 and v5.10-rc2.
** Summary changed: - Ubuntu 20.10- Undetected Data corruption in MPI workloads that use VSX for reductions on POWER9 DD2.1 systems + Undetected Data corruption in MPI workloads that use VSX for reductions on POWER9 DD2.1 systems -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1902694 Title: Undetected Data corruption in MPI workloads that use VSX for reductions on POWER9 DD2.1 systems To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-power-systems/+bug/1902694/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
