On Fri, Oct 09, 2020 at 11:24:38AM +0100, Mark Rutland wrote: > On Fri, Oct 09, 2020 at 10:43:18AM +0100, Mark Rutland wrote: > > Hi Qian, > > > > On Fri, Oct 09, 2020 at 09:51:15AM +0100, Will Deacon wrote: > > > On Thu, Oct 08, 2020 at 09:18:24PM -0400, Qian Cai wrote: > > > > On Mon, 2020-10-05 at 17:43 +0100, Mark Rutland wrote: > > > > > The current initialization of the per-cpu offset register is difficult > > > > > to follow and this initialization is not always early enough for > > > > > upcoming instrumentation with KCSAN, where the instrumentation callbacks > > > > > use the per-cpu offset. > > > > > > > > > > To make it possible to support KCSAN, and to simplify reasoning about > > > > > early bringup code, let's initialize the per-cpu offset earlier, before > > > > > we run any C code that may consume it. To do so, this patch adds a new > > > > > init_this_cpu_offset() helper that's called before the usual > > > > > primary/secondary start functions. For consistency, this is also used to > > > > > re-initialize the per-cpu offset after the runtime per-cpu areas have > > > > > been allocated (which can change CPU0's offset). > > > > > > > > > > So that init_this_cpu_offset() isn't subject to any instrumentation that > > > > > might consume the per-cpu offset, it is marked with noinstr, preventing > > > > > instrumentation. > > > > > > > > > > Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx> > > > > > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > > > > > Cc: James Morse <james.morse@xxxxxxx> > > > > > Cc: Will Deacon <will@xxxxxxxxxx> > > > > > > > > Reverting this commit on the top of today's linux-next fixed an issue that > > > > Thunder X2 is unable to boot: > > > > > > > > .config: https://gitlab.com/cailca/linux-mm/-/blob/master/arm64.config > > > > Sorry about this. :/ > > > > Will, to save you reading all the below, I think the right thing to do > > for now is to revert this. > > > > Looking at the assembly, task_cpu() gets instrumented (which puts this > > patch on dodgy ground generally and I think warrants the revert), but as > > it's instrumented with KASAN_INLINE that doesn't immediately explain the > > issue since the shadow should be up and so we shouldn't call the report > > function. I'll dig into this some more. > > Ok; that's my fault due to trying to do this before kasan_early_init. > > I see what's going on now. If you're happy to take a fixup instead of a > revert, patch below. Otherwise I'll a complete patch atop of the revert > after rc1. For now, I've reverted the patch on for-next/core and redone the tag. Will
