On Fri, 15 Dec, 2023 23:44:49 +1100 Michael Ellerman <m...@ellerman.id.au> wrote: > There are reports of kernels crashing due to stack overflow while > running OpenShift (Kubernetes). The primary contributor to the stack > usage seems to be openvswitch, which is used by OVN-Kubernetes (based on > OVN (Open Virtual Network)), but NFS also contributes in some stack > traces. > > There may be some opportunities to reduce stack usage in the openvswitch > code, but doing so potentially require tradeoffs vs performance, and > also requires testing across architectures. > > Looking at stack usage across the kernel (using -fstack-usage), shows > that ppc64le stack frames are on average 50-100% larger than the > equivalent function built for x86-64. Which is not surprising given the > minimum stack frame size is 32 bytes on ppc64le vs 16 bytes on x86-64. > > So increase the default stack size to 32KB for the modern 64-bit Book3S > platforms, ie. pseries (virtualised) and powernv (bare metal). That > leaves the older systems like G5s, and the AmigaOne (pasemi) with a 16KB > stack which should be sufficient on those machines. > > Signed-off-by: Michael Ellerman <m...@ellerman.id.au> > ---
We noticed this change is causing assembler issues for us when building the kernel. make ARCH=powerpc KERNELRELEASE=6.8.0-rc2_for_upstream_debug_2024_02_06_20_01 KBUILD_BUILD_VERSION=1 arch/powerpc/kernel/switch.S: Assembler messages: arch/powerpc/kernel/switch.S:249: Error: operand out of range (0x000000000000fe50 is not between 0xffffffffffff8000 and 0x0000000000007fff) make[6]: *** [scripts/Makefile.build:361: arch/powerpc/kernel/switch.o] Error 1 make[5]: *** [scripts/Makefile.build:481: arch/powerpc/kernel] Error 2 make[5]: *** Waiting for unfinished jobs.... make[4]: *** [scripts/Makefile.build:481: arch/powerpc] Error 2 make[4]: *** Waiting for unfinished jobs.... make[3]: *** [Makefile:1921: .] Error 2 The issue lies with the do_switch_64 macro. -- Thanks, Rahul Rameshbabu
