We are running low on CPU feature bits, so we only want to use them when
it's really necessary.
CPU_FTR_SUBCORE is only used in one place, and only in C, so we don't
need it in order to make asm patching work. It can only be set on
"Power8" CPUs, which in practice means POWER8, POWER8E and POWER8NVL.
There are no plans to implement it on future CPUs, but if there ever
were we could retrofit it then.
Although KVM uses subcores, it never looks at the CPU feature, it either
looks at the ISA level or the threads_per_subcore value.
So drop the CPU feature and do a PVR check instead. Drop the device tree
"subcore" feature as we no longer support doing anything with it, and we
will drop it from skiboot too.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Provide a dt_cpu_ftrs= cmdline option to disable the dt_cpu_ftrs CPU
feature discovery, and fall back to the "cputable" based version.
Also allow control of advertising unknown features to userspace and
with this parameter, and remove the clunky CONFIG option.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Add explicit early check of bootargs in dt_cpu_ftrs_init()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
The ibm,powerpc-cpu-features device tree binding describes CPU features with
ASCII names and extensible compatibility, privilege, and enablement metadata
that allows improved flexibility and compatibility with new hardware.
The interface is described in detail in ibm,powerpc-cpu-features.txt in this
patch.
Currently this code is not enabled by default, and there are no released
firmwares that provide the binding.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Michael Ellerman