Re: [PATCH v8 03/12] x86/mm: consolidate full flush threshold decision

Peter Zijlstra
2025-02-05T14:17:17Z

On Wed, Feb 05, 2025 at 01:20:07PM +0100, Peter Zijlstra wrote:
> On Tue, Feb 04, 2025 at 08:39:52PM -0500, Rik van Riel wrote:
>
> > diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> > index 6cf881a942bb..02e1f5c5bca3 100644
> > --- a/arch/x86/mm/tlb.c
> > +++ b/arch/x86/mm/tlb.c
> > @@ -1000,8 +1000,13 @@ static struct flush_tlb_info *get_flush_tlb_info(struct mm_struct *mm,
> > BUG_ON(this_cpu_inc_return(flush_tlb_info_idx) != 1);
> > #endif
> >
> > - info->start = start;
> > - info->end = end;
> > + /*
> > + * Round the start and end addresses to the page size specified
> > + * by the stride shift. This ensures partial pages at the end of
> > + * a range get fully invalidated.
> > + */
> > + info->start = round_down(start, 1 << stride_shift);
> > + info->end = round_up(end, 1 << stride_shift);
> > info->mm = mm;
> > info->stride_shift = stride_shift;
> > info->freed_tables = freed_tables;
>
> Rather than doing this; should we not fix whatever dodgy users are
> feeding us non-page-aligned addresses for invalidation?

That is, I feel this is worthy of WARN_ONCE at the very least.