# git rev-parse -q --verify d899987759d5c18c26204a3defc15a3fb55048c0^{commit}
# git fetch -q -n -f git://gitlab.ozlabs.ibm.com/mirror/linux-npiggin.git kerkins
# git rev-parse -q --verify d899987759d5c18c26204a3defc15a3fb55048c0^{commit}
d899987759d5c18c26204a3defc15a3fb55048c0
# git checkout -q -f -B kisskb d899987759d5c18c26204a3defc15a3fb55048c0
# git clean -qxdf
# < git log -1
# commit d899987759d5c18c26204a3defc15a3fb55048c0
# Author: Nicholas Piggin <npiggin@gmail.com>
# Date:   Thu Aug 2 17:36:57 2018 +1000
# 
#     powerpc/64s: reimplement book3s idle code in C
#     
#     Reimplement Book3S idle code in C, moving POWER7/8/9 implementation
#     speific HV idle code to the powernv platform code.
#     
#     Book3S assembly stubs are kept in common code and used only to save
#     the stack frame and non-volatile GPRs before executing architected
#     idle instructions, and restoring the stack and reloading GPRs then
#     returning to C after waking from idle.
#     
#     The complex logic dealing with threads and subcores, locking, SPRs,
#     HMIs, timebase resync, etc., is all done in C which makes it more
#     maintainable.
#     
#     This is not a strict translation to C code, there are some
#     significant differences:
#     
#     - Idle wakeup no longer uses the ->cpu_restore call to reinit SPRs,
#       but saves and restores them itself.
#     
#     - The optimisation where EC=ESL=0 idle modes did not have to save GPRs
#       or change MSR is restored, because it's now simple to do. ESL=1
#       sleeps that do not lose GPRs can use this optimization too.
#     
#     - KVM secondary entry and cede is now more of a call/return style
#       rather than branchy. nap_state_lost is not required because KVM
#       always returns via NVGPR restoring path.
#     
#     Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
#     Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
#     
#     Left to do:
#     - KVM could use more review, it's pretty tricky. Not sure if what
#       I'm doing with the emergency stack is kosher. But it runs pretty fine
#       here with a POWER8 SMP+SMT guest. Possible to streamline
#       KVM cede code now that idle function saves nv gprs for us?
#     
#     Open question:
#     - Why does P9 restore some of the PMU SPRs (but not others), and
#       P8 only zeroes them? (A: Unclear. First pass conversion patch will not
#       try to tidy this up, but it will become much easier to do afterward).
#     
#     Since RFC v1:
#     - Now tested and working with POWER9 hash and radix.
#     - KVM support added. This took a bit of work to untangle and might
#       still have some issues, but POWER9 seems to work including hash on
#       radix with dependent threads mode.
#     - This snowballed a bit because of KVM and other details making it
#       not feasible to leave POWER7/8 code alone. That's only half done
#       at the moment.
#     - So far this trades about 800 lines of asm for 500 of C. With POWER7/8
#       support done it might be another hundred or so lines of C.
#     
#     Since RFC v2:
#     - Fixed deep state SLB reloading
#     - Now tested and working with POWER8.
#     - Accounted for most feedback.
#     
#     Since RFC v3:
#     - Rebased to powerpc merge + idle state bugfix
#     - Split SLB flush/restore code out and shared with MCE code (pseries
#       MCE patches can also use).
#     - More testing on POWER8 including KVM with secondaries.
#     - Performance testing looks good. EC=ESL=0 is about 5% faster, other
#       stop states look a little faster too.
#     - Adjusted SPR saving to handler POWER7, haven't tested it.
#     
#     Since submission v1:
#     - More review comments from Gautham.
#     - Rename isa3_ to isa300_ prefix.
#     - Tinkered with some comments, copyright notice, changelog.
#     - Cede and regular idle do not go via KVM secondary wakeup code path,
#       so hwthread_state stores and barriers can be simplified, and some
#       KVM code paths simplified a little.
#     
#     Since v2:
#     - Rebase, SLB reload patch has been merged.
#     - More testing. Tested machine check idle wakeup path with mambo stepping
#       through instructions.
# < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/x86_64-linux/bin/x86_64-linux-gcc --version
# < git log --format=%s --max-count=1 d899987759d5c18c26204a3defc15a3fb55048c0
# < make -s -j 48 ARCH=x86_64 O=/kisskb/build/npiggin_x86_64-allnoconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/x86_64-linux/bin/x86_64-linux-  allnoconfig
# make -s -j 48 ARCH=x86_64 O=/kisskb/build/npiggin_x86_64-allnoconfig_x86_64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/x86_64-linux/bin/x86_64-linux-  
Completed OK
# rm -rf /kisskb/build/npiggin_x86_64-allnoconfig_x86_64-gcc8
# Build took: 0:03:14.585538