On Thu, Jun 23, 2022 at 05:15:20PM +0200, Christian Borntraeger wrote:

stable team, please consider commit 3ae11dbcfac906a8c3a480e98660a823130dc16a It will noticeable reduce system overhead when this happens on multiple CPUs.

----snip---- commit 3ae11dbcfac906a8c3a480e98660a823130dc16a s390/mm: use non-quiescing sske for KVM switch to keyed guest 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 Link: https://lore.kernel.org/r/20220530092706.11637-3-borntraeger@linux.ibm.com Signed-off-by: Christian Borntraeger borntraeger@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com

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();

}

Now queued up to all stable branches (as you didn't mention otherwise...)

thanks,

greg k-h