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Mon, 27 Sep 2021 17:02:18 +0000 (GMT) Date: Mon, 27 Sep 2021 19:02:07 +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 9/9] s390/mm: optimize reset_guest_reference_bit() Message-ID: <20210927190207.4b1e487a@p-imbrenda> In-Reply-To: <20210909162248.14969-10-david@redhat.com> References: <20210909162248.14969-1-david@redhat.com> <20210909162248.14969-10-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: AESESzveP29-fVex9la2Gcm_TcSPcwXJ X-Proofpoint-ORIG-GUID: 6eEy48gifxIhW1q5wkzVafrPtnS0nwKj X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.182.1,Aquarius:18.0.790,Hydra:6.0.391,FMLib:17.0.607.475 definitions=2021-09-27_06,2021-09-24_02,2020-04-07_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 malwarescore=0 adultscore=0 mlxscore=0 phishscore=0 priorityscore=1501 impostorscore=0 bulkscore=0 suspectscore=0 mlxlogscore=999 lowpriorityscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109230001 definitions=main-2109270116 X-Rspamd-Queue-Id: 7D42D300010F X-Stat-Signature: 9amm3t1gxc9kqqmycachcygqj7i4iu15 Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=sDgYUJbH; spf=pass (imf09.hostedemail.com: domain of imbrenda@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=imbrenda@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com X-Rspamd-Server: rspam06 X-HE-Tag: 1632762148-214708 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 9 Sep 2021 18:22:48 +0200 David Hildenbrand wrote: > We already optimize get_guest_storage_key() to assume that if we don't have > a PTE table and don't have a huge page mapped that the storage key is 0. > > Similarly, optimize reset_guest_reference_bit() to simply do nothing if > there is no PTE table and no huge page mapped. > > Signed-off-by: David Hildenbrand Reviewed-by: Claudio Imbrenda > --- > arch/s390/mm/pgtable.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c > index 534939a3eca5..50ab2fed3397 100644 > --- a/arch/s390/mm/pgtable.c > +++ b/arch/s390/mm/pgtable.c > @@ -901,13 +901,23 @@ int reset_guest_reference_bit(struct mm_struct *mm, unsigned long addr) > pte_t *ptep; > int cc = 0; > > - if (pmd_lookup(mm, addr, &pmdp)) > + /* > + * If we don't have a PTE table and if there is no huge page mapped, > + * the storage key is 0 and there is nothing for us to do. > + */ > + switch (pmd_lookup(mm, addr, &pmdp)) { > + case -ENOENT: > + return 0; > + case 0: > + break; > + default: > return -EFAULT; > + } > > ptl = pmd_lock(mm, pmdp); > if (!pmd_present(*pmdp)) { > spin_unlock(ptl); > - return -EFAULT; > + return 0; > } > > if (pmd_large(*pmdp)) {