Re: [PATCH 29/30] tools/testing/vma: default VMA flag bits to 64-bit

[Gregory Price]

On Mon, Jun 29, 2026 at 01:23:40PM +0100, Lorenzo Stoakes wrote:
> With all of the sanitisers turned on, setting the VMA flag bits depth to
> 128 by default results in overly long build times.
> 
> Reduce this to 64 - we can always manipulate these later for testing of
> larger bitmaps as needed.
> 
> Signed-off-by: Lorenzo Stoakes <ljs@xxxxxxxxxx>

Seems like this causes instrumented inlining to go crazy.

static inline void bitmap_or(...) {
	if (small_const_nbits(nbits))
		*dst = *src1 | *src2;
	else
		__bitmap_or(dst, src1, src2, nbits);
	        ^^^^ this branch is being hit ^^^^
}

tl;dr: __bitmap_or() gets emitted and then the sanitizers have to
instrument a ton of inlined functions instead of the compiler simply
injecting a couple 'or' instructions.

if you wanted to keep the coverage you could do something like

# These can be varied to test different sizes.
NUM_VMA_FLAG_BITS ?= 64
NUM_MM_FLAG_BITS  ?= 64
CFLAGS += -DNUM_VMA_FLAG_BITS=$(NUM_VMA_FLAG_BITS) -DNUM_MM_FLAG_BITS=$(NUM_MM_FLAG_BITS)

w/ 

make NUM_VMA_FLAG_BITS=128

would let you still test the branch but not by default.

anyway:

Reviewed-by: Gregory Price <gourry@xxxxxxxxxx>

~Gregory