From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.4 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6D88AC433E2 for ; Wed, 2 Sep 2020 03:58:31 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0D8B9206EB for ; Wed, 2 Sep 2020 03:58:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="Lez2m5b2" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0D8B9206EB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id AE0DE6B005A; Tue, 1 Sep 2020 23:58:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A6B638E0003; Tue, 1 Sep 2020 23:58:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 95B1B8E0001; Tue, 1 Sep 2020 23:58:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0176.hostedemail.com [216.40.44.176]) by kanga.kvack.org (Postfix) with ESMTP id 7BDA46B005A for ; Tue, 1 Sep 2020 23:58:30 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 499CF180AD806 for ; Wed, 2 Sep 2020 03:58:30 +0000 (UTC) X-FDA: 77216764380.10.man97_301857b2709d Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin10.hostedemail.com (Postfix) with ESMTP id 1BBD216A0DD for ; Wed, 2 Sep 2020 03:58:30 +0000 (UTC) X-HE-Tag: man97_301857b2709d X-Filterd-Recvd-Size: 9123 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by imf01.hostedemail.com (Postfix) with ESMTP for ; Wed, 2 Sep 2020 03:58:29 +0000 (UTC) Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 0823WoJu151620; Tue, 1 Sep 2020 23:58:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=NRMxz31et6UNTlJA7+QKz+EOKxjkgpK3zxuT1c6AiN4=; b=Lez2m5b261V98rccfFzz0hwukbPMRg+fN6kpKMbUHKhoQx6ijiHRiHmZ5z7/SjEtQYIa Lotrl01VlG6KIIbqDAQ7eQdCrJOOgn91SVwSSQlK5kFFNRjIMAZNWSM/vApHas8Z9ypp 10pujNky2D9tyeDZU3GnQEWmrjm+UHgynRi/sxhWndiLR3n7XeJS2janOBgaT4V/Ej2/ Pc0QBGcQ7iWfP2rkuvEOGs1JstKp4ovpzGwSsrXpvndrk6Mdj7sRawxwtUiUzmwi0EJJ GLPdrHJ8Icf+KFWxCy0l6WwIhLdzvgmQENJQJY5Fg7mQYua1prtkWi4IzFlATglVucEl Ng== Received: from ppma06fra.de.ibm.com (48.49.7a9f.ip4.static.sl-reverse.com [159.122.73.72]) by mx0a-001b2d01.pphosted.com with ESMTP id 33a3dern4m-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 01 Sep 2020 23:58:17 -0400 Received: from pps.filterd (ppma06fra.de.ibm.com [127.0.0.1]) by ppma06fra.de.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 0823vMJ3016533; Wed, 2 Sep 2020 03:58:15 GMT Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by ppma06fra.de.ibm.com with ESMTP id 337e9h2k3j-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 02 Sep 2020 03:58:14 +0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 0823wCjS30998800 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 2 Sep 2020 03:58:12 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7544EA404D; Wed, 2 Sep 2020 03:58:12 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 89808A4055; Wed, 2 Sep 2020 03:58:09 +0000 (GMT) Received: from [9.199.61.124] (unknown [9.199.61.124]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 2 Sep 2020 03:58:09 +0000 (GMT) Subject: Re: [PATCH v3 13/13] mm/debug_vm_pgtable: populate a pte entry before fetching it To: Anshuman Khandual , linux-mm@kvack.org, akpm@linux-foundation.org Cc: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, linux-snps-arc@lists.infradead.org, x86@kernel.org, linux-arch@vger.kernel.org, Gerald Schaefer , Christophe Leroy , Vineet Gupta , Mike Rapoport , Qian Cai References: <20200827080438.315345-1-aneesh.kumar@linux.ibm.com> <20200827080438.315345-14-aneesh.kumar@linux.ibm.com> <7ef7c302-e7e6-570e-3100-5dd1bf9551be@linux.ibm.com> <4ba15b8f-ac90-17ec-9b95-0451e2a38e98@arm.com> From: "Aneesh Kumar K.V" Message-ID: <7de344c3-26ea-be34-4435-8842360ed565@linux.ibm.com> Date: Wed, 2 Sep 2020 09:28:08 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <4ba15b8f-ac90-17ec-9b95-0451e2a38e98@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-09-02_02:2020-09-01,2020-09-02 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 bulkscore=0 malwarescore=0 suspectscore=0 mlxlogscore=999 phishscore=0 lowpriorityscore=0 mlxscore=0 impostorscore=0 adultscore=0 priorityscore=1501 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009020028 X-Rspamd-Queue-Id: 1BBD216A0DD X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 9/2/20 9:19 AM, Anshuman Khandual wrote: >=20 >=20 > On 09/01/2020 03:28 PM, Aneesh Kumar K.V wrote: >> On 9/1/20 1:08 PM, Anshuman Khandual wrote: >>> >>> >>> On 09/01/2020 12:07 PM, Aneesh Kumar K.V wrote: >>>> On 9/1/20 8:55 AM, Anshuman Khandual wrote: >>>>> >>>>> >>>>> On 08/27/2020 01:34 PM, Aneesh Kumar K.V wrote: >>>>>> pte_clear_tests operate on an existing pte entry. Make sure that i= s not a none >>>>>> pte entry. >>>>>> >>>>>> Signed-off-by: Aneesh Kumar K.V >>>>>> --- >>>>>> =C2=A0=C2=A0 mm/debug_vm_pgtable.c | 6 ++++-- >>>>>> =C2=A0=C2=A0 1 file changed, 4 insertions(+), 2 deletions(-) >>>>>> >>>>>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c >>>>>> index 21329c7d672f..8527ebb75f2c 100644 >>>>>> --- a/mm/debug_vm_pgtable.c >>>>>> +++ b/mm/debug_vm_pgtable.c >>>>>> @@ -546,7 +546,7 @@ static void __init pgd_populate_tests(struct m= m_struct *mm, pgd_t *pgdp, >>>>>> =C2=A0=C2=A0 static void __init pte_clear_tests(struct mm_struct = *mm, pte_t *ptep, >>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 unsigned lon= g vaddr) >>>>>> =C2=A0=C2=A0 { >>>>>> -=C2=A0=C2=A0=C2=A0 pte_t pte =3D ptep_get(ptep); >>>>>> +=C2=A0=C2=A0=C2=A0 pte_t pte =3D=C2=A0 ptep_get_and_clear(mm, vad= dr, ptep); >>>>> >>>>> Seems like ptep_get_and_clear() here just clears the entry in prepa= ration >>>>> for a following set_pte_at() which otherwise would have been a prob= lem on >>>>> ppc64 as you had pointed out earlier i.e set_pte_at() should not up= date an >>>>> existing valid entry. So the commit message here is bit misleading. >>>>> >>>> >>>> and also fetch the pte value which is used further. >>>> >>>> >>>>>> =C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pr_debug("Validating = PTE clear\n"); >>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pte =3D __pte(pte_val(pte) |= RANDOM_ORVALUE); >>>>>> @@ -944,7 +944,7 @@ static int __init debug_vm_pgtable(void) >>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 p4d_t *p4dp, *saved_p4dp; >>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pud_t *pudp, *saved_pudp; >>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pmd_t *pmdp, *saved_pmdp, pm= d; >>>>>> -=C2=A0=C2=A0=C2=A0 pte_t *ptep; >>>>>> +=C2=A0=C2=A0=C2=A0 pte_t *ptep, pte; >>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pgtable_t saved_ptep; >>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pgprot_t prot, protnone; >>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 phys_addr_t paddr; >>>>>> @@ -1049,6 +1049,8 @@ static int __init debug_vm_pgtable(void) >>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 */ >>>>>> =C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ptep =3D pte_alloc_ma= p_lock(mm, pmdp, vaddr, &ptl); >>>>>> +=C2=A0=C2=A0=C2=A0 pte =3D pfn_pte(pte_aligned, prot); >>>>>> +=C2=A0=C2=A0=C2=A0 set_pte_at(mm, vaddr, ptep, pte); >>>>> >>>>> Not here, creating and populating an entry must be done in respecti= ve >>>>> test functions itself. Besides, this seems bit redundant as well. T= he >>>>> test pte_clear_tests() with the above change added, already >>>>> >>>>> - Clears the PTEP entry with ptep_get_and_clear() >>>> >>>> and fetch the old value set previously. >>> >>> In that case, please move above two lines i.e >>> >>> pte =3D pfn_pte(pte_aligned, prot); >>> set_pte_at(mm, vaddr, ptep, pte); >>> >>> from debug_vm_pgtable() to pte_clear_tests() and update it's argument= s >>> as required. >>> >> >> Frankly, I don't understand what these tests are testing. It all looks= like some random clear and set. >=20 > The idea here is to have some value with some randomness preferably, in > a given PTEP before attempting to clear the entry, in order to make sur= e > that pte_clear() is indeed clearing something of non-zero value. >=20 >> >> static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep, >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 unsigned long vaddr, unsigned lon= g pfn, >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pgprot_t prot) >> { >> >> =C2=A0=C2=A0=C2=A0=C2=A0pte_t pte =3D pfn_pte(pfn, prot); >> =C2=A0=C2=A0=C2=A0=C2=A0set_pte_at(mm, vaddr, ptep, pte); >> >> =C2=A0=C2=A0=C2=A0=C2=A0pte =3D=C2=A0 ptep_get_and_clear(mm, vaddr, p= tep); >=20 > Looking at this again, this preceding pfn_pte() followed by set_pte_at(= ) > is not really required. Its reasonable to start with what ever was ther= e > in the PTEP as a seed value which anyway gets added with RANDOM_ORVALUE= . > s/ptep_get/ptep_get_and_clear is sufficient to take care of the powerpc > set_pte_at() constraint. >=20 But the way test is written we had none pte before. That is why I added=20 that set_pte_at to put something there. With none pte the below sequence=20 fails. pte =3D __pte(pte_val(pte) | RANDOM_ORVALUE); set_pte_at(mm, vaddr, ptep, pte); because nobody is marking a _PAGE_PTE there. pte_t pte =3D pfn_pte(pfn, prot); pr_debug("Validating PTE clear\n"); pte =3D __pte(pte_val(pte) | RANDOM_ORVALUE); set_pte_at(mm, vaddr, ptep, pte); barrier(); pte_clear(mm, vaddr, ptep); pte =3D ptep_get(ptep); WARN_ON(!pte_none(pte)); will that work for you? -aneesh