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Tue, 14 Sep 2021 16:54:52 +0000 (GMT) Received: from p-imbrenda (unknown [9.145.8.12]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id 0706C52050; Tue, 14 Sep 2021 16:54:51 +0000 (GMT) Date: Tue, 14 Sep 2021 18:54:49 +0200 From: Claudio Imbrenda To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, Christian Borntraeger , Janosch Frank , Cornelia Huck , Heiko Carstens , Vasily Gorbik , Niklas Schnelle , Gerald Schaefer , Ulrich Weigand Subject: Re: [PATCH resend RFC 7/9] s390/mm: no need for pte_alloc_map_lock() if we know the pmd is present Message-ID: <20210914185449.42d7d5ca@p-imbrenda> In-Reply-To: <20210909162248.14969-8-david@redhat.com> References: <20210909162248.14969-1-david@redhat.com> <20210909162248.14969-8-david@redhat.com> Organization: IBM X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: CzbilcmD8M7zTU8rtsHxUbv_j4RhfGJE X-Proofpoint-ORIG-GUID: cQpGxFB86TjgA5GPQXTyYbkzLxtXB232 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.182.1,Aquarius:18.0.687,Hydra:6.0.235,FMLib:17.0.607.475 definitions=2020-10-13_15,2020-10-13_02,2020-04-07_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 adultscore=0 malwarescore=0 mlxlogscore=999 mlxscore=0 lowpriorityscore=0 clxscore=1015 impostorscore=0 phishscore=0 bulkscore=0 spamscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109030001 definitions=main-2109140090 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Thu, 9 Sep 2021 18:22:46 +0200 David Hildenbrand wrote: > pte_map_lock() is sufficient. Can you explain the difference and why it is enough? > > Signed-off-by: David Hildenbrand > --- > arch/s390/mm/pgtable.c | 15 +++------------ > 1 file changed, 3 insertions(+), 12 deletions(-) > > diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c > index 5fb409ff7842..4e77b8ebdcc5 100644 > --- a/arch/s390/mm/pgtable.c > +++ b/arch/s390/mm/pgtable.c > @@ -814,10 +814,7 @@ int set_guest_storage_key(struct mm_struct *mm, unsigned long addr, > } > spin_unlock(ptl); > > - ptep = pte_alloc_map_lock(mm, pmdp, addr, &ptl); > - if (unlikely(!ptep)) > - return -EFAULT; > - > + ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); > new = old = pgste_get_lock(ptep); > pgste_val(new) &= ~(PGSTE_GR_BIT | PGSTE_GC_BIT | > PGSTE_ACC_BITS | PGSTE_FP_BIT); > @@ -912,10 +909,7 @@ int reset_guest_reference_bit(struct mm_struct *mm, unsigned long addr) > } > spin_unlock(ptl); > > - ptep = pte_alloc_map_lock(mm, pmdp, addr, &ptl); > - if (unlikely(!ptep)) > - return -EFAULT; > - > + ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); > new = old = pgste_get_lock(ptep); > /* Reset guest reference bit only */ > pgste_val(new) &= ~PGSTE_GR_BIT; > @@ -977,10 +971,7 @@ int get_guest_storage_key(struct mm_struct *mm, unsigned long addr, > } > spin_unlock(ptl); > > - ptep = pte_alloc_map_lock(mm, pmdp, addr, &ptl); > - if (unlikely(!ptep)) > - return -EFAULT; > - > + ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); > pgste = pgste_get_lock(ptep); > *key = (pgste_val(pgste) & (PGSTE_ACC_BITS | PGSTE_FP_BIT)) >> 56; > paddr = pte_val(*ptep) & PAGE_MASK;