------- Comment From bssrika...@in.ibm.com 2018-02-27 00:21 EDT------- (In reply to comment #5) > When you say "Power9 DD 2.2 needs HMI fixup backport of..." in the original > bug description. Is this patchset required to boot P9 DD2.2?
We need this patch for KVM guest testing on DD 2.2 revision. Good explanation on why this is required is in commit pointed. ==========================================================_ Hypervisor maintenance interrupts (HMIs) are generated by various causes, signalled by bits in the hypervisor maintenance exception register (HMER). In most cases calling OPAL to handle the interrupt is the correct thing to do, but the "debug trigger" HMIs signalled by PPC bit 17 (bit 46) of HMER are used to invoke software workarounds for hardware bugs, and OPAL does not have any code to handle this cause. The debug trigger HMI is used in POWER9 DD2.0 and DD2.1 chips to work around a hardware bug in executing vector load instructions to cache inhibited memory. In POWER9 DD2.2 chips, it is generated when conditions are detected relating to threads being in TM (transactional memory) suspended mode when the core SMT configuration needs to be reconfigured. The kernel currently has code to detect the vector CI load condition, but only when the HMI occurs in the host, not when it occurs in a guest. If a HMI occurs in the guest, it is always passed to OPAL, and then we always re-sync the timebase, because the HMI cause might have been a timebase error, for which OPAL would re-sync the timebase, thus removing the timebase offset which KVM applied for the guest. Since we don't know what OPAL did, we don't know whether to subtract the timebase offset from the timebase, so instead we re-sync the timebase. This adds code to determine explicitly what the cause of a debug trigger HMI will be. This is based on a new device-tree property under the CPU nodes called ibm,hmi-special-triggers, if it is present, or otherwise based on the PVR (processor version register). The handling of debug trigger HMIs is pulled out into a separate function which can be called from the KVM guest exit code. If this function handles and clears the HMI, and no other HMI causes remain, then we skip calling OPAL and we proceed to subtract the guest timebase offset from the timebase. The overall handling for HMIs that occur in the host (i.e. not in a KVM guest) is largely unchanged, except that we now don't set the flag for the vector CI load workaround on DD2.2 processors. This also removes a BUG_ON in the KVM code. BUG_ON is generally not useful in KVM guest entry/exit code since it is difficult to handle the resulting trap gracefully. ==========================================================_ -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1751834 Title: Power9 DD 2.2 needs HMI fixup backport of upstream patch(d075745d893c78730e4a3b7a60fca23c2f764081) into kernel Status in The Ubuntu-power-systems project: New Status in linux package in Ubuntu: New Bug description: == Comment: #0 - Satheesh Rajendran <sathe...@in.ibm.com> - 2018-02-23 06:55:23 == ---Problem Description--- Power9 DD 2.2 needs HMI fixup backport of upstream patch(d075745d893c78730e4a3b7a60fca23c2f764081) into kernel ---uname output--- 4.15.0-10-generic Machine Type = power9 boston 2.2 (pvr 004e 1202) ---Debugger--- A debugger is not configured ---Steps to Reproduce--- commit d075745d893c78730e4a3b7a60fca23c2f764081 Author: Paul Mackerras <pau...@ozlabs.org> Date: Wed Jan 17 20:51:13 2018 +1100 KVM: PPC: Book3S HV: Improve handling of debug-trigger HMIs on POWER9 Dependancy commit, looks like already present. commit 5080332c2c893118dbc18755f35c8b0131cf0fc4 Author: Michael Neuling <mi...@neuling.org> Date: Fri Sep 15 15:25:48 2017 +1000 powerpc/64s: Add workaround for P9 vector CI load issue Contact Information = sathe...@in.ibm.com Stack trace output: no Oops output: no System Dump Info: The system is not configured to capture a system dump. *Additional Instructions for sathe...@in.ibm.com: -Attach sysctl -a output output to the bug. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-power-systems/+bug/1751834/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
