[kbuild-all] Re: arch/powerpc/kvm/book3s_hv_nested.c:264:6: error: stack frame size of 2304 bytes in function 'kvmhv_enter_nested_guest'

On 6/20/2021 4:59 PM, Nicholas Piggin wrote: > Excerpts from kernel test robot's message of April 3, 2021 8:47 pm: >> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master >> head: d93a0d43e3d0ba9e19387be4dae4a8d5b175a8d7 >> commit: 97e4910232fa1f81e806aa60c25a0450276d99a2 linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP* >> date: 3 weeks ago >> config: powerpc64-randconfig-r006-20210403 (attached as .config) >> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 0fe8af94688aa03c01913c2001d6a1a911f42ce6) >> reproduce (this is a W=1 build): >> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross >> chmod +x ~/bin/make.cross >> # install powerpc64 cross compiling tool for clang build >> # apt-get install binutils-powerpc64-linux-gnu >> # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit... >> git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git >> git fetch --no-tags linus master >> git checkout 97e4910232fa1f81e806aa60c25a0450276d99a2 >> # save the attached .config to linux build tree >> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=powerpc64 >> >> If you fix the issue, kindly add following tag as appropriate >> Reported-by: kernel test robot <lkp(a)intel.com&gt; >> >> All errors (new ones prefixed by >>): >> >>>> arch/powerpc/kvm/book3s_hv_nested.c:264:6: error: stack frame size of 2304 bytes in function 'kvmhv_enter_nested_guest' [-Werror,-Wframe-larger-than=] >> long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu) >> ^ >> 1 error generated. >> >> >> vim +/kvmhv_enter_nested_guest +264 arch/powerpc/kvm/book3s_hv_nested.c > > Not much changed here recently. It's not that big a concern because it's > only called in the KVM ioctl path, not in any deep IO paths or anything, > and doesn't recurse. Might be a bit of inlining or stack spilling put it > over the edge. It appears to be the fact that LLVM's PowerPC backend does not emit efficient byteswap assembly: https://github.com/ClangBuiltLinux/linux/issues/1292 https://bugs.llvm.org/show_bug.cgi?id=49610 > powerpc does make it an error though, would be good to avoid that so the > robot doesn't keep tripping over. Marking byteswap_pt_regs as 'noinline_for_stack' drastically reduces the stack usage. If that is an acceptable solution, I can send it along tomorrow.