Re: [PATCH 2/2] s390/pgtable: use non-quiescing sske for KVM switch to keyed

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Mon, 30 May 2022 11:27:06 +0200
Christian Borntraeger <borntraeger@linux.ibm.com> wrote:

> The switch to a keyed guest does not require a classic sske as the other
> guest CPUs are not accessing the key before the switch is complete.
> By using the NQ SSKE things are faster especially with multiple guests.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
> Suggested-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  arch/s390/mm/pgtable.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
> index 697df02362af..4909dcd762e8 100644
> --- a/arch/s390/mm/pgtable.c
> +++ b/arch/s390/mm/pgtable.c
> @@ -748,7 +748,7 @@ void ptep_zap_key(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
>  	pgste_val(pgste) |= PGSTE_GR_BIT | PGSTE_GC_BIT;
>  	ptev = pte_val(*ptep);
>  	if (!(ptev & _PAGE_INVALID) && (ptev & _PAGE_WRITE))
> -		page_set_storage_key(ptev & PAGE_MASK, PAGE_DEFAULT_KEY, 1);
> +		page_set_storage_key(ptev & PAGE_MASK, PAGE_DEFAULT_KEY, 0);
>  	pgste_set_unlock(ptep, pgste);
>  	preempt_enable();
>  }