Re: [PATCH v14 13/13] x86/mm: only invalidate final translations with INVLPGB

[Borislav Petkov]

On Mon, Mar 03, 2025 at 02:40:49PM -0800, Dave Hansen wrote:
> On 2/25/25 19:00, Rik van Riel wrote:
> >  static inline void __invlpgb_flush_user_nr_nosync(unsigned long pcid,
> >  						  unsigned long addr,
> >  						  u16 nr,
> > -						  bool pmd_stride)
> > +						  bool pmd_stride,
> > +						  bool freed_tables)
> >  {
> > -	__invlpgb(0, pcid, addr, nr, pmd_stride, INVLPGB_PCID | INVLPGB_VA);
> > +	u8 flags = INVLPGB_PCID | INVLPGB_VA;
> > +
> > +	if (!freed_tables)
> > +		flags |= INVLPGB_FINAL_ONLY;
> > +
> > +	__invlpgb(0, pcid, addr, nr, pmd_stride, flags);
> >  }
> 
> I'm not sure this is OK.
> 
> Think of a hugetlbfs mapping with shared page tables. Say you had a
> 1GB-sized and 1GB-aligned mapping. It might zap the one PUD that it
> needs, set tlb->cleared_puds=1 but it never sets ->freed_tables because
> it didn't actually free the shared page table page.
> 
> I'd honestly just throw this patch out of the series for now. All of the
> other TLB invalidation that the kernel does implicitly toss out the
> mid-level paging structure caches.

Right, I guess we can revisit this later, once the dust settles.

Thx.

-- 
Regards/Gruss,
    Boris.

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