On 21/02/18 17:39, Andrew Jones wrote: > On Thu, Feb 15, 2018 at 10:03:02PM +0100, Christoffer Dall wrote: >> The debug save/restore functions can be improved by using the has_vhe() >> static key instead of the instruction alternative. Using the static key >> uses the same paradigm as we're going to use elsewhere, it makes the >> code more readable, and it generates slightly better code (no >> stack setups and function calls unless necessary). >> >> We also use a static key on the restore path, because it will be >> marginally faster than loading a value from memory. >> >> Finally, we don't have to conditionally clear the debug dirty flag if >> it's set, we can just clear it. >> >> Reviewed-by: Marc Zyngier <marc.zyngier@xxxxxxx> >> Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> >> --- >> >> Notes: >> Changes since v1: >> - Change dot to comma in comment >> - Rename __debug_restore_spe to __debug_restore_spe_nvhe >> >> arch/arm64/kvm/hyp/debug-sr.c | 26 ++++++++++++-------------- >> 1 file changed, 12 insertions(+), 14 deletions(-) >> > > Maybe after this series is merged, if there are any hyp_alternate_select's > left, we can replace all the remaining ones with has_vhe() and then just > completely remove hyp_alternate_select. Note that older compilers (such as GCC 4.8) will generate horrible code with static keys, as they do not support "asm goto". Not that I want to preserve the home brew hyp_alternate_select mechanism, but I just want to make it plain that some distros will definitely suffer from the transition. M. -- Jazz is not dead. It just smells funny...
