[PATCH] powerpc: Always select HAVE_EFFICIENT_UNALIGNED_ACCESS

[PATCH] powerpc: Always select HAVE_EFFICIENT_UNALIGNED_ACCESS

[Michael Ellerman]

Currently powerpc selects HAVE_EFFICIENT_UNALIGNED_ACCESS in all cases
but one. The exception is if the kernel is being built little endian and
explicitly targetted for Power7.

The combination of Power7 and little endian was never commercially
supported, or widely used. It was only ever possible on bare metal
machines, using unofficial firmware, or in qemu guests hosted on those
machines.

The bare metal firmware support for Power7 was removed in 2019, see
skiboot commit 16b7ae64 ("Remove POWER7 and POWER7+ support").

Little endian kernel builds were switched to target Power8 or later in
2018, in commit a73657ea19ae ("powerpc/64: Add GENERIC_CPU support for
little endian"). Since then it's only been possible to boot a Power7/LE
kernel by explicitly building for Power7.

So drop the exception and always select HAVE_EFFICIENT_UNALIGNED_ACCESS.
If anyone does still have a Power7/LE machine it should hopefully
continue to boot, just with some performance penality, and if not they
can report a bug.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
 arch/powerpc/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 4c466acdc70d..7dc46dc2e387 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -211,7 +211,7 @@ config PPC
 	select HAVE_DYNAMIC_FTRACE_WITH_ARGS	if MPROFILE_KERNEL || PPC32
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS	if MPROFILE_KERNEL || PPC32
 	select HAVE_EBPF_JIT
-	select HAVE_EFFICIENT_UNALIGNED_ACCESS	if !(CPU_LITTLE_ENDIAN && POWER7_CPU)
+	select HAVE_EFFICIENT_UNALIGNED_ACCESS
 	select HAVE_FAST_GUP
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_FUNCTION_DESCRIPTORS	if PPC64_ELF_ABI_V1
-- 
2.37.2

Re: [PATCH] powerpc: Always select HAVE_EFFICIENT_UNALIGNED_ACCESS

[Michael Ellerman]

On Fri, 16 Sep 2022 23:15:23 +1000, Michael Ellerman wrote:
> Currently powerpc selects HAVE_EFFICIENT_UNALIGNED_ACCESS in all cases
> but one. The exception is if the kernel is being built little endian and
> explicitly targetted for Power7.
> 
> The combination of Power7 and little endian was never commercially
> supported, or widely used. It was only ever possible on bare metal
> machines, using unofficial firmware, or in qemu guests hosted on those
> machines.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc: Always select HAVE_EFFICIENT_UNALIGNED_ACCESS
      https://git.kernel.org/powerpc/c/ecf8f36446f53866727d9670df1746f8d20130a8

cheers