From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Robert Richter <robert.richter@cavium.com>
Cc: Will Deacon <will.deacon@arm.com>,
Robert Richter <rric@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
David Daney <david.daney@cavium.com>,
Hanjun Guo <hanjun.guo@linaro.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] arm64: mm: Fix memmap to be initialized for the entire section
Date: Sun, 20 Nov 2016 17:07:44 +0000 [thread overview]
Message-ID: <CAKv+Gu-2uGJGovqQL-gbB54u=fQ9L9YUbDdRo6u3oWqF6znn6Q@mail.gmail.com> (raw)
In-Reply-To: <20161117151805.GJ2151@rric.localdomain>
On 17 November 2016 at 15:18, Robert Richter <robert.richter@cavium.com> wrote:
> Thanks for your answer.
>
> On 17.11.16 14:25:29, Will Deacon wrote:
>> On Wed, Nov 09, 2016 at 08:51:32PM +0100, Robert Richter wrote:
>> > Thus, I don't see where my patch breaks code. Even acpi_os_ioremap()
>> > keeps the same behaviour as before since it still uses memblock_is_
>> > memory(). Could you more describe your concerns why do you think this
>> > patch breaks the kernel and moves the problem somewhere else? I
>> > believe it fixes the problem at all.
>>
>> acpi_os_ioremap always ends up in __ioremap_caller, regardless of
>> memblock_is_memory(). __ioremap_caller then fails if pfn_valid is true.
>
> But that's the reason my patch changed the code to use memblock_is_
> map_memory() instead. I was looking into the users of pfn_valid() esp.
> in arm64 code and changed it where required.
>
> This week I looked into the kernel again for code that might break by
> a pfn_valid() change. I found try_ram_remap() in memremap.c that has
> changed behaviour now, but this is explicit for MEMREMAP_WB, so it
> should be fine.
>
> Maybe it might be better to use page_is_ram() in addition to
> pfn_valid() where necessary. This should work now after commit:
>
> e7cd190385d1 arm64: mark reserved memblock regions explicitly in iomem
>
> I still think pfn_valid() is not the correct use to determine the mem
> attributes for mappings, there are further checks required.
>
> The risk of breaking something with my patch is small and limited only
> to the mapping of efi reserved regions (which is the state of 4.4). If
> something breaks anyway it can easily be fixed by adding more checks
> to pfn_valid() as suggested above.
>
As I noted before, it looks to me like setting CONFIG_HOLES_IN_ZONE is
the correct way to address this. However, doing that does uncover a
bug in move_freepages() where the VM_BUG_ON_PAGE() dereferences struct
page fields before the pfn_valid_within() check, so it seems those
need to be switched around.
Robert, you mentioned that CONFIG_HOLES_IN_ZONE seems inappropriate
for sparsemem. Care to elaborate why?
next prev parent reply other threads:[~2016-11-20 17:07 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-06 9:52 [PATCH] arm64: mm: Fix memmap to be initialized for the entire section Robert Richter
2016-10-06 10:00 ` Ard Biesheuvel
2016-10-06 16:11 ` Robert Richter
2016-10-17 18:58 ` Robert Richter
2016-10-27 16:01 ` Will Deacon
2016-10-28 9:19 ` Robert Richter
2016-11-07 21:05 ` Will Deacon
2016-11-09 19:51 ` Robert Richter
2016-11-17 14:25 ` Will Deacon
2016-11-17 15:18 ` Robert Richter
2016-11-20 17:07 ` Ard Biesheuvel [this message]
2016-11-23 21:15 ` Robert Richter
2016-11-23 21:25 ` Ard Biesheuvel
2016-11-24 13:42 ` Robert Richter
2016-11-24 13:44 ` Ard Biesheuvel
2016-11-24 13:51 ` Robert Richter
2016-11-24 13:58 ` Ard Biesheuvel
2016-11-24 14:11 ` Robert Richter
2016-11-24 14:23 ` Ard Biesheuvel
2016-11-24 15:09 ` Robert Richter
2016-11-24 19:26 ` Robert Richter
2016-11-24 19:42 ` Ard Biesheuvel
2016-11-25 11:29 ` Robert Richter
2016-11-25 12:28 ` Ard Biesheuvel
2016-11-25 17:01 ` Ard Biesheuvel
2016-10-18 10:18 ` Mark Rutland
2016-10-18 15:02 ` Robert Richter
2016-10-10 15:33 ` David Daney
2016-11-01 16:55 ` Robert Richter
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