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powerpc/64s: system call rfscv workaround for TM bugs
commit ae7aaec upstream. The rfscv instruction does not work correctly with the fake-suspend mode in POWER9, which can end up with the hypervisor restoring an incorrect checkpoint. Work around this by setting the _TIF_RESTOREALL flag if a system call returns to a transaction active state, causing rfid to be used instead of rfscv to return, which will do the right thing. The contents of the registers are irrelevant because they will be overwritten in this case anyway. Fixes: 7fa95f9 ("powerpc/64s: system call support for scv/rfscv instructions") Reported-by: Eirik Fuller <efuller@redhat.com> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210908101718.118522-1-npiggin@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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