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Sat, 14 Aug 2021 02:57:49 +0000 (UTC) Received: from [10.64.54.103] (vpn2-54-103.bne.redhat.com [10.64.54.103]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2097F5C1A1; Sat, 14 Aug 2021 02:57:41 +0000 (UTC) Reply-To: Gavin Shan Subject: Re: [PATCH v6 00/12] mm/debug_vm_pgtable: Enhancements To: Vineet Gupta , Anshuman Khandual , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, gerald.schaefer@linux.ibm.com, aneesh.kumar@linux.ibm.com, christophe.leroy@csgroup.eu, cai@lca.pw, catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, chuhu@redhat.com, shan.gavin@gmail.com, arcml References: <20210809092631.1888748-1-gshan@redhat.com> <25018384-acc5-dcf7-5125-378499ab4555@kernel.org> From: Gavin Shan Message-ID: <828d44a7-525f-c507-00d1-8e323c8956bc@redhat.com> Date: Sat, 14 Aug 2021 12:57:38 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: <25018384-acc5-dcf7-5125-378499ab4555@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Rspamd-Queue-Id: EB0379000701 Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=VJ3DPrys; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf23.hostedemail.com: domain of gshan@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=gshan@redhat.com X-Rspamd-Server: rspam04 X-Stat-Signature: ssa16975j3qaojnufuo7otik9377jtrf X-HE-Tag: 1628909873-68285 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: Hi Vineet, On 8/14/21 5:43 AM, Vineet Gupta wrote: > On 8/13/21 2:25 AM, Gavin Shan wrote: >> On 8/12/21 9:11 PM, Anshuman Khandual wrote: >>> On 8/9/21 2:56 PM, Gavin Shan wrote: >>>> There are couple of issues with current implementations and this ser= ies >>>> tries to resolve the issues: >>>> >>>> =C2=A0=C2=A0 (a) All needed information are scattered in variables, = passed to various >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 test functions. The code is org= anized in pretty much relaxed fashion. >>>> >>>> =C2=A0=C2=A0 (b) The page isn't allocated from buddy during page tab= le entry modifying >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 tests. The page can be invalid,= conflicting to the implementations >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 of set_xxx_at() on ARM64. The t= arget page is accessed so that the >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 iCache can be flushed when exec= ution permission is given on ARM64. >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Besides, the target page can be= unmapped and accessing to it causes >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 kernel crash. >>>> >>>> "struct pgtable_debug_args" is introduced to address issue (a). For = issue >>>> (b), the used page is allocated from buddy in page table entry modif= ying >>>> tests. The corresponding tets will be skipped if we fail to allocate= the >>>> (huge) page. For other test cases, the original page around to kerne= l >>>> symbol (@start_kernel) is still used. >>>> >>>> The patches are organized as below. PATCH[2-10] could be combined to= one >>>> patch, but it will make the review harder: >>>> >>>> =C2=A0=C2=A0 PATCH[1] introduces "struct pgtable_debug_args" as plac= e holder of all >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 n= eeded information. With it, the old and new implementation >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 c= an coexist. >>>> =C2=A0=C2=A0 PATCH[2-10] uses "struct pgtable_debug_args" in various= test functions. >>>> =C2=A0=C2=A0 PATCH[11] removes the unused code for old implementatio= n. >>>> =C2=A0=C2=A0 PATCH[12] fixes the issue of corrupted page flag for AR= M64 >>>> >>>> Changelog >>>> =3D=3D=3D=3D=3D=3D=3D=3D=3D >>>> v6: >>>> =C2=A0=C2=A0=C2=A0 * Populate saved page table entry pointers after >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 they're allocated in init_args() (Ans= human) >>>> =C2=A0=C2=A0=C2=A0 * Fix imbalanced preemption count issue by replac= ing >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pte_alloc_mmap() with pte_alloc() in = init_args() (syzbot) >>> >>> + vgupta@kernel.org >=20 > Please also keep linux-snps-arc CC'ed for ARC changes. >=20 Sure. >>> >>> Hello Gavin/Vineet, >>> >>> This series still need to be tested on ARC ? >>> >> >> Yes, I'm unable to test ARC as it's not supported by QEMU yet. >> It would great if Vineet can give it a try on ARC :) >=20 > We do have a working QEMU (in the process of being upstreamed) you coul= d try > https://github.com/foss-for-synopsys-dwc-arc-processors/qemu #master >=20 > Is this code in some shared git repo we can pull - instead of apply 8 f= iles. >=20 Here is repo with v6 series included. Please help to have a try. https://github.com/gwshan/linux # kvm/arm64_debug I tried to build the cross-compiler with buildroot with following 2 repos. Unfortunately, none of them worked for me. The QEMU binary can be built successfully with the provided repo though. [1] git://github.com/foss-for-synopsys-dwc-arc-processors/buildroot.git (branch: master) There are build errors after choosing little-endian ARM from "make menuconfig" [2] https://github.com/buildroot/buildroot (branch: master) The build is successful, but the kernel can't be built because of the following errors: =20 # make ARCH=3Darc CROSS_COMPILE=3Darc-linux- axs103_smp_defconfig # make -j 40 : LD vmlinux.o arc-linux-ld: error: attempting to link /home/gavin/sandbox/buildroo= t/buildroot.arc/output/host/lib /gcc/arc-buildroot-linux-uclibc/10.2.0/libgcc.a(_muldi3.o) with a bi= nary vmlinux.o of different architecture Thanks, Gavin