Public bug reported: -- Problem Description -- POWER9 DD2.1 and earlier has an issue where some cache inhibited vector load will return bad data. The workaround is two part, one firmware/microcode part triggers HMI interrupts when hitting such loads, the other part is this patch which then emulates the instructions in Linux.
The affected instructions are limited to lxvd2x, lxvw4x, lxvb16x and lxvh8x. When an instruction triggers the HMI, all threads in the core will be sent to the HMI handler, not just the one running the vector load. In general, these spurious HMIs are detected by the emulation code and we just return back to the running process. Unfortunately, if a spurious interrupt occurs on a vector load that's to normal memory we have no way to detect that it's spurious (unless we walk the page tables, which is very expensive). In this case we emulate the load but we need do so using a vector load itself to ensure 128bit atomicity is preserved. Some additional debugfs emulated instruction counters are added also. In order to solve this bug, we need to cherry pick the following patch https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/commit/?h=next&id=5080332c2c893118dbc18755f35c8b0131cf0fc4 ** Affects: linux (Ubuntu) Importance: Medium Assignee: Ubuntu on IBM Power Systems Bug Triage (ubuntu-power-triage) Status: Triaged ** Tags: architecture-ppc64le bugnameltc-159632 severity-critical targetmilestone-inin1710 ** Tags added: architecture-ppc64le bugnameltc-159632 severity-critical targetmilestone-inin1710 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1721070 Title: powerpc/64s: Add workaround for P9 vector CI load issuenext To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1721070/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
