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From:   Qian Cai <cai@lca.pw>
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Subject: Re: [PATCH v15 00/23] Generic page walk and ptdump
Date:   Thu, 5 Dec 2019 08:15:02 -0500
Message-Id: <A22DE6B7-23A1-41FA-AF82-9613778277C7@lca.pw>
References: <20191204163235.GA1597@arm.com>
Cc:     David Hildenbrand <david@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux-MM <linux-mm@kvack.org>,
        Mark Rutland <Mark.Rutland@arm.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        =?utf-8?Q?J=C3=A9r=C3=B4me_Glisse?= <jglisse@redhat.com>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Andy Lutomirski <luto@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        James Morse <James.Morse@arm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Will Deacon <will@kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "Liang, Kan" <kan.liang@linux.intel.com>,
        Thomas Hellstrom <thellstrom@vmware.com>
In-Reply-To: <20191204163235.GA1597@arm.com>
To:     Steven Price <Steven.Price@arm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> On Dec 4, 2019, at 11:32 AM, Steven Price <Steven.Price@arm.com> wrote:
>=20
> I've bisected this problem and it's a merge conflict with:
>=20
> ace88f1018b8 ("mm: pagewalk: Take the pagetable lock in walk_pte_range()")=


Sigh, how does that commit end up merging in the mainline without going thro=
ugh Andrew=E2=80=99s tree and missed all the linux-next testing? It was merg=
ed into the mainline Oct 4th?

> Reverting that commit "fixes" the problem. That commit adds a call to
> pte_offset_map_lock(), however that isn't necessarily safe when
> considering an "unusual" mapping in the kernel. Combined with my patch
> set this leads to the BUG when walking the kernel's page tables.
>=20
> At this stage I think it's best if Andrew drops my series and I'll try
> to rework it on top -rc1 fixing up this conflict and the other x86
> 32-bit issue that has cropped up.