[RFC PATCH V3 3/6] arm: mm: implement get_user_pages_fast

[Peter Zijlstra]

On Wed, Mar 12, 2014 at 01:40:20PM +0000, Steve Capper wrote:
> +void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
> +			  pmd_t *pmdp)
> +{
> +	pmd_t pmd = pmd_mksplitting(*pmdp);
> +	VM_BUG_ON(address & ~PMD_MASK);
> +	set_pmd_at(vma->vm_mm, address, pmdp, pmd);
> +
> +	/* dummy IPI to serialise against fast_gup */
> +	smp_call_function(thp_splitting_flush_sync, NULL, 1);
> +}

do you really need to IPI the entire machine? Wouldn't the mm's TLB
invalidate mask be sufficient?