linux-kernel - Re: linux-next: manual merge of the arm64 tree with the arm64-fixes tree

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Date:   Thu, 21 Jul 2022 17:14:58 +0100
From:   Will Deacon <will@...nel.org>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Peter Collingbourne <pcc@...gle.com>
Subject: Re: linux-next: manual merge of the arm64 tree with the arm64-fixes
 tree

Hi Stephen,

On Thu, Jul 21, 2022 at 08:45:17PM +1000, Stephen Rothwell wrote:
> On Thu, 21 Jul 2022 09:45:12 +1000 Stephen Rothwell <sfr@...b.auug.org.au> wrote:
> >
> > Today's linux-next merge of the arm64 tree got a conflict in:
> > 
> >   arch/arm64/kernel/head.S
> > 
> > between commit:
> > 
> >   f7b4c3b82e7d ("arm64: set UXN on swapper page tables")
> > 
> > from the arm64-fixes tree and commits:
> > 
> >   e42ade29e3bc ("arm64: head: split off idmap creation code")
> >   c3cee924bd85 ("arm64: head: cover entire kernel image in initial ID map")
> > 
> > from the arm64 tree.
> > 
> > I didn't know if the change from the former was still needed after the
> > changes in the latter, so I left it out for now.
> 
> OK, so my arm64 defconfig build produced these errors:
> 
> arch/arm64/kernel/head.S: Assembler messages:
> arch/arm64/kernel/head.S:334: Error: immediate cannot be moved by a single instruction
> arch/arm64/kernel/head.S:343: Error: immediate cannot be moved by a single instruction
> arch/arm64/kernel/head.S:354: Error: immediate cannot be moved by a single instruction
> arch/arm64/kernel/head.S:379: Error: immediate cannot be moved by a single instruction
> arch/arm64/mm/proc.S:296: Error: immediate cannot be moved by a single instruction
> 
> So I tried this patch:
> 
> From: Stephen Rothwell <sfr@...b.auug.org.au>
> Date: Thu, 21 Jul 2022 20:21:36 +1000
> Subject: [PATCH] fixup for "arm64: set UXN on swapper page tables"
> 
> Signed-off-by: Stephen Rothwell <sfr@...b.auug.org.au>
> ---
>  arch/arm64/kernel/head.S | 8 ++++----
>  arch/arm64/mm/proc.S     | 2 +-
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index cefe6a73ee54..aa7c58689f68 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -331,7 +331,7 @@ SYM_FUNC_START_LOCAL(create_idmap)
>  	adrp	x0, init_idmap_pg_dir
>  	adrp	x3, _text
>  	adrp	x6, _end + MAX_FDT_SIZE + SWAPPER_BLOCK_SIZE
> -	mov	x7, SWAPPER_RX_MMUFLAGS
> +	mov_q	x7, SWAPPER_RX_MMUFLAGS

[...]

I think Marc posted something similar here:

https://lore.kernel.org/r/20220721124244.903567-1-maz@kernel.org

but in further discussion offline (and echoed on that thread), we've decided
to drop f7b4c3b82e7d ("arm64: set UXN on swapper page tables") for now; the
issue it addresses doesn't affect the hardware which is readily available at
the moment so we'll just get it into -stable instead rather than disrupt
everything at this stage in the release cycle.

> So I gave up and left arm64 broken for today :-(

No problem, thank you for trying and hopefully it will be better tomorrow
once we've dropped that commit.

Will