# git rev-parse -q --verify d9c57d3ed52a92536f5fa59dc5ccdd58b4875076^{commit}
# git fetch -q -n -f git://gitlab.ozlabs.ibm.com/linuxppc/linux.git fixes-test
# git rev-parse -q --verify d9c57d3ed52a92536f5fa59dc5ccdd58b4875076^{commit}
d9c57d3ed52a92536f5fa59dc5ccdd58b4875076
# git checkout -q -f -B kisskb d9c57d3ed52a92536f5fa59dc5ccdd58b4875076
# git clean -qxdf
# < git log -1
# commit d9c57d3ed52a92536f5fa59dc5ccdd58b4875076
# Author: Nicholas Piggin <npiggin@gmail.com>
# Date:   Thu Jul 8 21:26:22 2021 +1000
# 
#     KVM: PPC: Book3S HV Nested: Sanitise H_ENTER_NESTED TM state
#     
#     The H_ENTER_NESTED hypercall is handled by the L0, and it is a request
#     by the L1 to switch the context of the vCPU over to that of its L2
#     guest, and return with an interrupt indication. The L1 is responsible
#     for switching some registers to guest context, and the L0 switches
#     others (including all the hypervisor privileged state).
#     
#     If the L2 MSR has TM active, then the L1 is responsible for
#     recheckpointing the L2 TM state. Then the L1 exits to L0 via the
#     H_ENTER_NESTED hcall, and the L0 saves the TM state as part of the exit,
#     and then it recheckpoints the TM state as part of the nested entry and
#     finally HRFIDs into the L2 with TM active MSR. Not efficient, but about
#     the simplest approach for something that's horrendously complicated.
#     
#     Problems arise if the L1 exits to the L0 with a TM state which does not
#     match the L2 TM state being requested. For example if the L1 is
#     transactional but the L2 MSR is non-transactional, or vice versa. The
#     L0's HRFID can take a TM Bad Thing interrupt and crash.
#     
#     Fix this by disallowing H_ENTER_NESTED in TM[T] state entirely, and then
#     ensuring that if the L1 is suspended then the L2 must have TM active,
#     and if the L1 is not suspended then the L2 must not have TM active.
#     
#     Fixes: 360cae313702 ("KVM: PPC: Book3S HV: Nested guest entry via hypercall")
#     Cc: stable@vger.kernel.org # v4.20+
#     Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
#     Acked-by: Michael Neuling <mikey@neuling.org>
#     Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/x86_64-linux/bin/x86_64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/x86_64-linux/bin/x86_64-linux-ld --version
# < git log --format=%s --max-count=1 d9c57d3ed52a92536f5fa59dc5ccdd58b4875076
# < make -s -j 32 ARCH=x86_64 O=/kisskb/build/powerpc-fixes_x86_64-allnoconfig_x86_64-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/x86_64-linux/bin/x86_64-linux-  allnoconfig
# < make -s -j 32 ARCH=x86_64 O=/kisskb/build/powerpc-fixes_x86_64-allnoconfig_x86_64-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/x86_64-linux/bin/x86_64-linux-  help
# make -s -j 32 ARCH=x86_64 O=/kisskb/build/powerpc-fixes_x86_64-allnoconfig_x86_64-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/x86_64-linux/bin/x86_64-linux-  olddefconfig
# make -s -j 32 ARCH=x86_64 O=/kisskb/build/powerpc-fixes_x86_64-allnoconfig_x86_64-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/x86_64-linux/bin/x86_64-linux-  
Completed OK
# rm -rf /kisskb/build/powerpc-fixes_x86_64-allnoconfig_x86_64-gcc4.9
# Build took: 0:02:01.358745