Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Mon, 30 Mar 2020 14:51:21 +0100
From: Will Deacon <>
To: Ard Biesheuvel <>
Subject: Re: [RFC PATCH] arm64: remove CONFIG_DEBUG_ALIGN_RODATA feature

On Sun, Mar 29, 2020 at 04:12:58PM +0200, Ard Biesheuvel wrote:
> When CONFIG_DEBUG_ALIGN_RODATA is enabled, kernel segments mapped with
> different permissions (r-x for .text, r-- for .rodata, rw- for .data,
> etc) are rounded up to 2 MiB so they can be mapped more efficiently.
> In particular, it permits the segments to be mapped using level 2
> block entries when using 4k pages, which is expected to result in less
> TLB pressure.
> However, the mappings for the bulk of the kernel will use level 2
> entries anyway, and the misaligned fringes are organized such that they
> can take advantage of the contiguous bit, and use far fewer level 3
> entries than would be needed otherwise.
> This makes the value of this feature dubious at best, and since it is not
> enabled in defconfig or in the distro configs, it does not appear to be
> in wide use either. So let's just remove it.
> Signed-off-by: Ard Biesheuvel <>
> ---
>  arch/arm64/Kconfig.debug                  | 13 -------------
>  arch/arm64/include/asm/memory.h           | 12 +-----------
>  drivers/firmware/efi/libstub/arm64-stub.c |  8 +++-----
>  3 files changed, 4 insertions(+), 29 deletions(-)

Acked-by: Will Deacon <>

But I would really like to go a step further and rip out the block mapping
support altogether so that we can fix non-coherent DMA aliases:


Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.