Re: [PATCH v17 21/23] arm64: mm: Convert mm/dump.c to use walk_page_range()

From: Ard Biesheuvel <ardb@kernel.org>
To: Steven Price <steven.price@arm.com>
Cc: "Mark Rutland" <Mark.Rutland@arm.com>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Catalin Marinas" <Catalin.Marinas@arm.com>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>,
	"Jérôme 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>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Will Deacon" <will@kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	"Liang, Kan" <kan.liang@linux.intel.com>
Subject: Re: [PATCH v17 21/23] arm64: mm: Convert mm/dump.c to use walk_page_range()
Date: Mon, 17 Feb 2020 11:16:23 +0100	[thread overview]
Message-ID: <CAKv+Gu-iLwjZvavQud9o+5nTB0ORAAn32qKMScxYHJ64k7HExA@mail.gmail.com> (raw)
In-Reply-To: <ee4f53ec-601b-3698-1479-f7aeaada38ad@arm.com>

On Mon, 17 Feb 2020 at 11:01, Steven Price <steven.price@arm.com> wrote:
>
> On 16/02/2020 16:25, Ard Biesheuvel wrote:
> > On Wed, 18 Dec 2019 at 17:25, Steven Price <steven.price@arm.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@arm.com>
> >> Signed-off-by: Steven Price <steven.price@arm.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?
>

Not at all, I just got confused.

IIRC we did have support for dumping the EFI pages tables on 32-bit
ARM at *some* point, but it obviously wasn't your patch that removed
it.

Apologies for the noise.

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