powerpc: Add denormalisation exception handling for POWER6/7
On POWER6 and POWER7 if the input operand to an instruction is a
denormalised single precision binary floating point value we can take
a denormalisation exception where it's expected that the hypervisor
(HV=1) will fix up the inputs before the instruction is run.
This adds code to handle this denormalisation exception for POWER6 and
POWER7.
It also add a CONFIG_PPC_DENORMALISATION option and sets it in
pseries/ppc64_defconfig.
This is useful on bare metal systems only. Based on patch from Milton
Miller.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 98e513b..748ccaa 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -560,6 +560,14 @@
when dealing with POWER5 cpus at a cost of slightly increased
overhead in some places. If unsure say N here.
+config PPC_DENORMALISATION
+ bool "PowerPC denormalisation exception handling"
+ depends on PPC_BOOK3S_64
+ default "n"
+ ---help---
+ Add support for handling denormalisation of single precision
+ values. Useful for bare metal only. If unsure say Y here.
+
config CMDLINE_BOOL
bool "Default bootloader kernel arguments"