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From:   Qian Cai <cai@lca.pw>
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Subject: Re: [mm/debug] fa6726c1e7: kernel_BUG_at_include/linux/mm.h
Date:   Mon, 27 Apr 2020 22:51:04 -0400
Message-Id: <D30E4C88-408A-438B-803B-D9F8F82D87A7@lca.pw>
References: <096a07fc-4525-feb6-5658-40bcffbd0a58@arm.com>
Cc:     kernel test robot <lkp@intel.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Christophe Leroy <christophe.leroy@c-s.fr>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Ingo Molnar <mingo@kernel.org>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Vineet Gupta <vgupta@synopsys.com>,
        Will Deacon <will@kernel.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>, lkp@lists.01.org
In-Reply-To: <096a07fc-4525-feb6-5658-40bcffbd0a58@arm.com>
To:     Anshuman Khandual <Anshuman.Khandual@arm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> On Apr 27, 2020, at 10:35 PM, Anshuman Khandual <Anshuman.Khandual@arm.com=
> wrote:
>=20
> Letting CONFIG_DEBUG_VM_PGTABLE enabled via CONFIG_EXPERT for unsupported
> platforms i.e without ARCH_HAS_DEBUG_VM_PGTABLE, was a conscious decision
> meant to expand it's adaptability and coverage without requiring any code
> (i.e Kconfig) change. The easier it is to enable the test on unsupported
> platforms right now, more folks are likely to try it out thus increasing
> it's probability to get fixed on those platforms. That is a valid enough
> reason to have CONFIG_EXPERT based enablement method, IMHO. Also even with=

> CONFIG_EXPERT set, CONFIG_DEBUG_VM_PGTABLE does not get enabled by default=

> automatically.

No, I am talking about PAE. There is a distinction between known broken that=
 nobody cares (like arm32) and in-progress/unknown status (like s390).

Also, it is not very nice to introduce regressions for robots when testing P=
AE because they always select CONFIG__EXPERT and CONFIG_DEBUG_VM.=