Re: [PATCH v12 5/5] arm64: Allow huge io mappings again

[Chintan Pandya]

On 6/4/2018 5:44 PM, Will Deacon wrote:
> On Fri, Jun 01, 2018 at 06:09:18PM +0530, Chintan Pandya wrote:
> > Huge mappings have had stability issues due to stale
> > TLB entry and memory leak issues. Since, those are
> > addressed in this series of patches, it is now safe
> > to allow huge mappings.
> >
> > Signed-off-by: Chintan Pandya <cpandya@xxxxxxxxxxxxxx>
> > ---
> >   arch/arm64/mm/mmu.c | 18 ++----------------
> >   1 file changed, 2 insertions(+), 16 deletions(-)
> >
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > index 6e7e16c..c65abc4 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -934,15 +934,8 @@ int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
> >   {
> >   	pgprot_t sect_prot = __pgprot(PUD_TYPE_SECT |
> >   					pgprot_val(mk_sect_prot(prot)));
> > -	pud_t new_pud = pfn_pud(__phys_to_pfn(phys), sect_prot);
> > -
> > -	/* Only allow permission changes for now */
> > -	if (!pgattr_change_is_safe(READ_ONCE(pud_val(*pudp)),
> > -				   pud_val(new_pud)))
> > -		return 0;
>
> Do you actually need to remove these checks? If we're doing
> break-before-make properly, then the check won't fire but it would be
> good to keep it there so we can catch misuse of these in future.
>
> In other words, can we drop this patch?

Yes, we don't need this patch as BBM is happening before this. I missed
that. I'll remove this patch in v13.

> Will

Chintan
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