linux-kernel - Re: [PATCH RFC 1/2] s390x: mm: allow mixed page table types (2k and 4k)

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Date:   Thu, 1 Jun 2017 14:59:49 +0200
From:   David Hildenbrand <david@...hat.com>
To:     kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Thomas Huth <thuth@...hat.com>,
        Christian Borntraeger <borntraeger@...ibm.com>
Subject: Re: [PATCH RFC 1/2] s390x: mm: allow mixed page table types (2k and
 4k)


> diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
> index d4d409b..b22c2b6 100644
> --- a/arch/s390/mm/pgtable.c
> +++ b/arch/s390/mm/pgtable.c
> @@ -196,7 +196,7 @@ static inline pgste_t ptep_xchg_start(struct mm_struct *mm,
>  {
>  	pgste_t pgste = __pgste(0);
>  
> -	if (mm_has_pgste(mm)) {
> +	if (pgtable_has_pgste(mm, __pa(ptep))) {
>  		pgste = pgste_get_lock(ptep);
>  		pgste = pgste_pte_notify(mm, addr, ptep, pgste);
>  	}
> @@ -207,7 +207,7 @@ static inline pte_t ptep_xchg_commit(struct mm_struct *mm,
>  				    unsigned long addr, pte_t *ptep,
>  				    pgste_t pgste, pte_t old, pte_t new)
>  {
> -	if (mm_has_pgste(mm)) {
> +	if (pgtable_has_pgste(mm, __pa(ptep))) {
>  		if (pte_val(old) & _PAGE_INVALID)
>  			pgste_set_key(ptep, pgste, new, mm);
>  		if (pte_val(new) & _PAGE_INVALID) 

I think these two checks are wrong. We really have to test here the
mapcount bit only (relying on mm_has_pgste(mm) is wrong in case global
vm.allocate_pgste ist set).

But before I continue working on this, I think it makes sense to clarify
if something like that would be acceptable at all.

-- 

Thanks,

David