On 6/18/19 12:53 PM, Arnd Bergmann wrote: > ARM64 randdconfig builds regularly run into a build error, especially > when NUMA_BALANCING and SPARSEMEM are enabled but not SPARSEMEM_VMEMMAP: > > #error "KASAN: not enough bits in page flags for tag" > > The last-cpuid bits are already contitional on the available space, > so the result of the calculation is a bit random on whether they > were already left out or not. > > Adding the kasan tag bits before last-cpuid makes it much more likely > to end up with a successful build here, and should be reliable for > randconfig at least, as long as that does not randomize NR_CPUS > or NODES_SHIFT but uses the defaults. > > In order for the modified check to not trigger in the x86 vdso32 code > where all constants are wrong (building with -m32), enclose all the > definitions with an #ifdef. > Why not keep "#error "KASAN: not enough bits in page flags for tag"" under "#ifdef CONFIG_KASAN_SW_TAGS" ?
