A bisect for arch/powerpc/ shows this is the first bad commit on 4.15: $ git bisect bad 7d10952e8a56f87a53fc57594078555a9dfd4a07 is the first bad commit commit 7d10952e8a56f87a53fc57594078555a9dfd4a07 Author: Michael Ellerman <m...@ellerman.id.au> Date: Thu May 28 00:58:42 2020 +1000
powerpc/64s: Save FSCR to init_task.thread.fscr after feature init BugLink: https://bugs.launchpad.net/bugs/1885176 commit 912c0a7f2b5daa3cbb2bc10f303981e493de73bd upstream. At boot the FSCR is initialised via one of two paths. On most systems it's set to a hard coded value in __init_FSCR(). On newer skiboot systems we use the device tree CPU features binding, where firmware can tell Linux what bits to set in FSCR (and HFSCR). In both cases the value that's configured at boot is not propagated into the init_task.thread.fscr value prior to the initial fork of init (pid 1), which means the value is not used by any processes other than swapper (the idle task). For the __init_FSCR() case this is OK, because the value in init_task.thread.fscr is initialised to something sensible. However it does mean that the value set in __init_FSCR() is not used other than for swapper, which is odd and confusing. The bigger problem is for the device tree CPU features case it prevents firmware from setting (or clearing) FSCR bits for use by user space. This means all existing kernels can not have features enabled/disabled by firmware if those features require setting/clearing FSCR bits. We can handle both cases by saving the FSCR value into init_task.thread.fscr after we have initialised it at boot. This fixes the bug for device tree CPU features, and will allow us to simplify the initialisation for the __init_FSCR() case in a future patch. Fixes: 5a61ef74f269 ("powerpc/64s: Support new device tree binding for discovering CPU features") Cc: sta...@vger.kernel.org # v4.12+ Signed-off-by: Michael Ellerman <m...@ellerman.id.au> Link: https://lore.kernel.org/r/20200527145843.2761782-3-...@ellerman.id.au Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> Signed-off-by: Kamal Mostafa <ka...@canonical.com> Signed-off-by: Khalid Elmously <khalid.elmou...@canonical.com> :040000 040000 9c654d310ed9b7c4a1cf16620d120ec93624eda3 05b34a61190e63ccde3b7d02e2183dc64b32c812 M arch $ git bisect log git bisect start '--' 'arch/powerpc/' \# bad: [f4daf25f7f8608d1c14c85ea0b73c9e1e1eb2dba] UBUNTU: Ubuntu-4.15.0-114.115 git bisect bad f4daf25f7f8608d1c14c85ea0b73c9e1e1eb2dba \# good: [495149ddc61a5997857fda041ccd4c81cac46e00] UBUNTU: Ubuntu-4.15.0-112.113 git bisect good 495149ddc61a5997857fda041ccd4c81cac46e00 \# bad: [07ad1246146fa49430d2455bd45db1c8da4d521c] powerpc/perf/hv-24x7: Fix inconsistent output values incase multiple hv-24x7 events run git bisect bad 07ad1246146fa49430d2455bd45db1c8da4d521c \# good: [f30471f4138df69bd4585d91c1f31a282daa41e7] powerpc/64s: Don't let DT CPU features set FSCR_DSCR git bisect good f30471f4138df69bd4585d91c1f31a282daa41e7 \# bad: [0e198dfae237e9a9654d87b7c6df12146feaec26] sched/core: Fix illegal RCU from offline CPUs git bisect bad 0e198dfae237e9a9654d87b7c6df12146feaec26 \# bad: [7d10952e8a56f87a53fc57594078555a9dfd4a07] powerpc/64s: Save FSCR to init_task.thread.fscr after feature init git bisect bad 7d10952e8a56f87a53fc57594078555a9dfd4a07 \# first bad commit: [7d10952e8a56f87a53fc57594078555a9dfd4a07] powerpc/64s: Save FSCR to init_task.thread.fscr after feature init -- 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/1888332 Title: [Potential Regression] dscr_inherit_exec_test from powerpc in ubuntu_kernel_selftests failed on B/E/F Status in ubuntu-kernel-tests: New Status in linux package in Ubuntu: Incomplete Status in linux source package in Eoan: Incomplete Bug description: Issue found on 5.3.0-64.58 with P8 node modoc (passed with P9 node) # selftests: powerpc/dscr: dscr_inherit_exec_test # test: dscr_inherit_exec_test # tags: git_version:unknown # Parent DSCR 1 was not inherited over exec (kernel value) # Child didn't exit cleanly # failure: dscr_inherit_exec_test not ok 5 selftests: powerpc/dscr: dscr_inherit_exec_test # exit=1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-kernel-tests/+bug/1888332/+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