As this patch set solved the performance issue and even led to the highest scores I ever saw on the benchmark tool I used, let me add a:

Tested-by: Howard Spoelstra <hsp.cat7@gmail.com>

On Thu, Jan 30, 2020 at 12:50 AM Richard Henderson <richard.henderson@linaro.org> wrote:

The first two address the performance regression noticed
by Howard Spoelstra. The last two are just something I
noticed at the same time.

r~

Richard Henderson (4):
target/ppc: Use probe_access for LSW, STSW
target/ppc: Use probe_access for LMW, STMW
target/ppc: Remove redundant mask in DCBZ
target/ppc: Use probe_write for DCBZ

target/ppc/mem_helper.c | 197 +++++++++++++++++++++++++++++++++-------
1 file changed, 162 insertions(+), 35 deletions(-)

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2.20.1