Subject: [RFC PATCH 0/2] 2nd attempt at PR KVM + SCV and syscall

From: Nicholas Piggin <[email-masked]>
Date: Tue, 18 Jan 2022 15:58:19 +1000

The more I looked into system call emulation, the harder it seems to
get.

Second proposal is remove it entirely because it's already broken, and
just boot-time restrict SCV support if we run with PR possible, in hash
mode, on pseries. Unfortunately that catches Power9 PowerVM, but at
least OpenPOWER and Power10 by default is okay.

We probably have to do this as a minimal backport at first even if we
did later decide we need to fix things in a better way because it looks
like it would take a lot of work.

Any comments? mpe helped with looking at the tracing logic and history
of the code (thanks) but any mistakes are mine, Naveen are we on the
right track here?

Thanks,
Nick

Nicholas Piggin (2):
  powerpc/64: remove system call instruction emulation
  KVM: PPC: Book3S PR: Disable SCV when running AIL is disabled

 arch/powerpc/kernel/exceptions-64s.S |  4 ++++
 arch/powerpc/kernel/setup_64.c       | 15 ++++++++++++
 arch/powerpc/kvm/book3s_pr.c         | 20 +++++++++++-----
 arch/powerpc/lib/sstep.c             | 36 ----------------------------
 4 files changed, 33 insertions(+), 42 deletions(-)

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