Re: [PATCH v3 06/11] selftests: Fix arm64 IO barriers to match kernel

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, Jul 16, 2026 at 04:22:10PM -0700, Nathan Chancellor wrote:
> On Thu, Jul 16, 2026 at 02:03:22PM -0300, Jason Gunthorpe wrote:
> > The tools/include readl/writel MMIO accessors on arm64 use
> > inner-shareable barriers (dmb ish) while the kernel uses
> > outer-shareable (dmb osh).  Fix them to match.
> > 
> > Add __io_bw() and __io_ar() definitions matching the kernel's
> > arch/arm64/include/asm/io.h, including the dummy control dependency
> > in __io_ar() that orders MMIO reads against all subsequent
> > instructions.
> > 
> > Assisted-by: Claude:claude-opus-4.6
> > Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ...
> > diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk
> > index f02cc8a2e4ae32..fdd22df9174b88 100644
> > --- a/tools/testing/selftests/lib.mk
> > +++ b/tools/testing/selftests/lib.mk
> > @@ -5,9 +5,14 @@ ifneq ($(filter %/,$(LLVM)),)
> >  LLVM_PREFIX := $(LLVM)
> >  else ifneq ($(filter -%,$(LLVM)),)
> >  LLVM_SUFFIX := $(LLVM)
> > +else ifneq ($(LLVM),1)
> > +$(error Invalid value for LLVM, see Documentation/kbuild/llvm.rst)
> >  endif
> >  
> >  CLANG := $(LLVM_PREFIX)clang$(LLVM_SUFFIX)
> > +LD := $(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX)
> > +# Selftests link through $(CC), so point clang at the LLVM linker.
> > +LDFLAGS += --ld-path=$(LD)
> >  
> >  CLANG_TARGET_FLAGS_arm          := arm-linux-gnueabi
> >  CLANG_TARGET_FLAGS_arm64        := aarch64-linux-gnu
> 
> Was this hunk intended to be included in this change? It is not
> mentioned anywhere. I assume this is the only reason that the LLVM folks
> were CC'd on this series.

Er no, I can no longer remember what that was about, it wasn't in
v2. Actually I also see I forgot to delete this patch as Will
suggested in the first place.

Jason