linux-kernel - Re: [PATCH v17 21/23] arm64: mm: Convert mm/dump.c to use walk_page

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Date:   Mon, 17 Feb 2020 10:01:00 +0000
From:   Steven Price <steven.price@....com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>, Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <Catalin.Marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        James Morse <James.Morse@....com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Rutland <Mark.Rutland@....com>,
        "Liang, Kan" <kan.liang@...ux.intel.com>
Subject: Re: [PATCH v17 21/23] arm64: mm: Convert mm/dump.c to use
 walk_page_range()

On 16/02/2020 16:25, Ard Biesheuvel wrote:
> On Wed, 18 Dec 2019 at 17:25, Steven Price <steven.price@....com> wrote:
>>
>> Now walk_page_range() can walk kernel page tables, we can switch the
>> arm64 ptdump code over to using it, simplifying the code.
>>
>> Reviewed-by: Catalin Marinas <catalin.marinas@....com>
>> Signed-off-by: Steven Price <steven.price@....com>
> 
> I did not realize this at the time, but this patch removes the ability
> to dump the EFI page tables on 32-bit ARM. Was that intentional?

No that wasn't intentional, but I can't instantly see how this change
affects 32-bit ARM.

<snip (files in arch/arm64)>
>> diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
>> index 899b803842bb..9dda2602c862 100644
>> --- a/drivers/firmware/efi/arm-runtime.c
>> +++ b/drivers/firmware/efi/arm-runtime.c
>> @@ -27,7 +27,7 @@
>>
>>  extern u64 efi_system_table;
>>
>> -#ifdef CONFIG_ARM64_PTDUMP_DEBUGFS
>> +#if defined(CONFIG_PTDUMP_DEBUGFS) && defined(CONFIG_ARM64)

The previous define was *ARM64* so should never have been true when
building for arm. The new condition should be equivalent (arm64 &&
ptdump enabled).

Am I missing something?

Steve