linux-kernel - Re: [PATCH v15 00/23] Generic page walk and ptdump

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Message-Id: <A22DE6B7-23A1-41FA-AF82-9613778277C7@lca.pw>
Date:   Thu, 5 Dec 2019 08:15:02 -0500
From:   Qian Cai <cai@....pw>
To:     Steven Price <Steven.Price@....com>
Cc:     David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        Mark Rutland <Mark.Rutland@....com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jérôme Glisse <jglisse@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        James Morse <James.Morse@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "Liang, Kan" <kan.liang@...ux.intel.com>,
        Thomas Hellstrom <thellstrom@...are.com>
Subject: Re: [PATCH v15 00/23] Generic page walk and ptdump



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

Sigh, how does that commit end up merging in the mainline without going through Andrew’s tree and missed all the linux-next testing? It was merged 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.
> 
> 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.