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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 7 Jun 2019 06:35:58 +0100 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x575Zveh17629308 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 7 Jun 2019 05:35:57 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BF9634C052; Fri, 7 Jun 2019 05:35:57 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2A3F44C05C; Fri, 7 Jun 2019 05:35:57 +0000 (GMT) Received: from skywalker.linux.ibm.com (unknown [9.124.35.207]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 7 Jun 2019 05:35:56 +0000 (GMT) X-Mailer: emacs 26.2 (via feedmail 11-beta-1 I) From: "Aneesh Kumar K.V" To: Nicholas Piggin , linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 2/2] powerpc/64s: __find_linux_pte synchronization vs pmdp_invalidate In-Reply-To: <20190607035636.5446-2-npiggin@gmail.com> References: <20190607035636.5446-1-npiggin@gmail.com> <20190607035636.5446-2-npiggin@gmail.com> Date: Fri, 07 Jun 2019 11:05:56 +0530 MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 x-cbid: 19060705-0028-0000-0000-000003782026 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19060705-0029-0000-0000-000024380282 Message-Id: <87wohyez43.fsf@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-06-07_02:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906070039 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: Nicholas Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Nicholas Piggin writes: > The change to pmdp_invalidate to mark the pmd with _PAGE_INVALID broke > the synchronisation against lock free lookups, __find_linux_pte's > pmd_none check no longer returns true for such cases. > > Fix this by adding a check for this condition as well. > Reviewed-by: Aneesh Kumar K.V > Fixes: da7ad366b497 ("powerpc/mm/book3s: Update pmd_present to look at _PAGE_PRESENT bit") > Cc: Christophe Leroy > Suggested-by: Aneesh Kumar K.V > Signed-off-by: Nicholas Piggin > --- > arch/powerpc/mm/pgtable.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c > index db4a6253df92..533fc6fa6726 100644 > --- a/arch/powerpc/mm/pgtable.c > +++ b/arch/powerpc/mm/pgtable.c > @@ -372,13 +372,25 @@ pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea, > pdshift = PMD_SHIFT; > pmdp = pmd_offset(&pud, ea); > pmd = READ_ONCE(*pmdp); > + > /* > - * A hugepage collapse is captured by pmd_none, because > - * it mark the pmd none and do a hpte invalidate. > + * A hugepage collapse is captured by this condition, see > + * pmdp_collapse_flush. > */ > if (pmd_none(pmd)) > return NULL; > > +#ifdef CONFIG_PPC_BOOK3S_64 > + /* > + * A hugepage split is captured by this condition, see > + * pmdp_invalidate. > + * > + * Huge page modification can be caught here too. > + */ > + if (pmd_is_serializing(pmd)) > + return NULL; > +#endif > + > if (pmd_trans_huge(pmd) || pmd_devmap(pmd)) { > if (is_thp) > *is_thp = true; > -- > 2.20.1