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Wed, 17 May 2023 10:35:48 GMT Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B38752004B; Wed, 17 May 2023 10:35:48 +0000 (GMT) Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C636820043; Wed, 17 May 2023 10:35:47 +0000 (GMT) Received: from p-imbrenda (unknown [9.152.224.66]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 17 May 2023 10:35:47 +0000 (GMT) Date: Wed, 17 May 2023 12:35:46 +0200 From: Claudio Imbrenda To: Hugh Dickins Subject: Re: [PATCH 15/23] s390: allow pte_offset_map_lock() to fail Message-ID: <20230517123546.672fb9b0@p-imbrenda> In-Reply-To: <94aec8fe-383f-892-dcbf-d4c14e460a7@google.com> References: <77a5d8c-406b-7068-4f17-23b7ac53bc83@google.com> <94aec8fe-383f-892-dcbf-d4c14e460a7@google.com> Organization: IBM X-Mailer: Claws Mail 4.1.1 (GTK 3.24.37; 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: 8y_E68kURQ0ih8Y_-pXj5N6bPDOiuEZv X-Proofpoint-ORIG-GUID: ot2a0roI6HKgv_SkGdPLAhcx7gRQDDOX X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.957,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-05-17_02,2023-05-16_01,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 bulkscore=0 clxscore=1011 mlxscore=0 phishscore=0 spamscore=0 mlxlogscore=972 malwarescore=0 lowpriorityscore=0 impostorscore=0 priorityscore=1501 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2304280000 definitions=main-2305170081 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-ia64@vger.kernel.org, David Hildenbrand , Catalin Marinas , Qi Zheng , linux-kernel@vger.kernel.org, Max Filippov , sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, Will Deacon , Greg Ungerer , linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, Helge Deller , x86@kernel.org, Russell King , Matthew Wilcox , Geert Uytterhoeven , Christian Borntraeger , Alexandre Ghiti , Heiko Carstens , linux-m68k@lists.linux-m68k.org, John Paul Adrian Glaubitz , John David Anglin , Suren Baghdasaryan , linux-arm-kernel@lists.infradead.org, Chris Zankel , Michal Simek , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, linux-mm@kvack.org, linux-mips@vger.kernel.org, Palmer Dabbelt , "Kirill A. Shutemov" , "Aneesh Kumar K.V" , Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S. Miller" , Mike Rapoport , Mike Kravetz Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, 9 May 2023 22:01:16 -0700 (PDT) Hugh Dickins wrote: > In rare transient cases, not yet made possible, pte_offset_map() and > pte_offset_map_lock() may not find a page table: handle appropriately. > > Signed-off-by: Hugh Dickins > --- > arch/s390/kernel/uv.c | 2 ++ > arch/s390/mm/gmap.c | 2 ++ > arch/s390/mm/pgtable.c | 12 +++++++++--- > 3 files changed, 13 insertions(+), 3 deletions(-) > > diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c > index cb2ee06df286..3c62d1b218b1 100644 > --- a/arch/s390/kernel/uv.c > +++ b/arch/s390/kernel/uv.c > @@ -294,6 +294,8 @@ int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb) > > rc = -ENXIO; > ptep = get_locked_pte(gmap->mm, uaddr, &ptelock); > + if (!ptep) > + goto out; > if (pte_present(*ptep) && !(pte_val(*ptep) & _PAGE_INVALID) && pte_write(*ptep)) { > page = pte_page(*ptep); > rc = -EAGAIN; > diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c > index dc90d1eb0d55..d198fc9475a2 100644 > --- a/arch/s390/mm/gmap.c > +++ b/arch/s390/mm/gmap.c > @@ -2549,6 +2549,8 @@ static int __zap_zero_pages(pmd_t *pmd, unsigned long start, > spinlock_t *ptl; > > ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); > + if (!ptep) > + break; so if pte_offset_map_lock fails, we abort and skip both the failed entry and the rest of the entries? can pte_offset_map_lock be retried immediately if it fails? (consider that we currently don't allow THP with KVM guests) Would something like this: do { ptep = pte_offset_map_lock(...); mb(); /* maybe? */ } while (!ptep); make sense? otherwise maybe it's better to return an error and retry the whole walk_page_range() in s390_enable_sie() ? it's a slow path anyway. > if (is_zero_pfn(pte_pfn(*ptep))) > ptep_xchg_direct(walk->mm, addr, ptep, __pte(_PAGE_INVALID)); > pte_unmap_unlock(ptep, ptl); [...]