With INIT_STACK_ALL_PATTERN or INIT_STACK_ALL_ZERO enabled the kernel will be compiled with -ftrivial-auto-var-init=<...> which causes initialization of stack variables at function entry time. In order to avoid the performance impact that comes with this users can use the "uninitialized" attribute to prevent such initialization. In particular code sections in s390 specific kernel code which use floating point or vector registers all come with a 520 byte stack variable to save already in use registers, if required. If the above named config options are enabled this stack variable will always be initialized on function entry in addition to saving register contents, which contradicts the intend (performance improvement) of such code sections. Therefore provide a generic __uninitialized macro and an s390 specific DECLARE_KERNEL_FPU_ONSTACK() macro which provides a kernel fpu variable with an __uninitialized attribute, and convert all existing code to use this. If people are ok which this approach, I'd like to carry this via the s390 tree to avoid potential merge conflicts, since there is a larger fpu code rework pending Thanks, Heiko Heiko Carstens (2): Compiler Attributes: Add __uninitialized macro s390/fpu: make use of __uninitialized macro arch/s390/crypto/chacha-glue.c | 2 +- arch/s390/crypto/crc32-vx.c | 2 +- arch/s390/include/asm/fpu/types.h | 3 +++ arch/s390/kernel/sysinfo.c | 2 +- include/linux/compiler_attributes.h | 12 ++++++++++++ lib/raid6/s390vx.uc | 4 ++-- 6 files changed, 20 insertions(+), 5 deletions(-) -- 2.40.1
