Re: [PATCH 1/2] xen/arm32: head: Rework how the fixmap and early UART mapping are prepared

[Michal Orzel <michal.orzel@xxxxxxx>]

Hi Julien,

On 02/11/2023 00:30, Julien Grall wrote:
> 
> 
> From: Julien Grall <jgrall@xxxxxxxxxx>
> 
> Since commit 5e213f0f4d2c ("xen/arm32: head: Widen the use of the
> temporary mapping"), boot_second (used to cover regions like Xen and
> the fixmap) will not be mapped if the identity mapping overlap.
> 
> So it is ok to prepare the fixmap table and link it in boot_second
> earlier. With that, the fixmap can also be used earlier via the
> temporary mapping.
> 
> Therefore split setup_fixmap() in two:
>     * The table is now linked in create_page_tables() because
>       the boot page tables needs to be recreated for every CPU.
>     * The early UART mapping is only added for the boot CPU0 as the
>       fixmap table is not cleared when secondary CPUs boot.
> 
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
> ---
>  xen/arch/arm/arm32/head.S | 48 ++++++++-------------------------------
>  1 file changed, 9 insertions(+), 39 deletions(-)
> 
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index 33b038e7e0ca..fec2433e568f 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -183,12 +183,16 @@ past_zImage:
>          bl    check_cpu_mode
>          bl    cpu_init
>          bl    create_page_tables
> +        /* Add the UART mapping if requested */
> +#ifdef CONFIG_EARLY_PRINTK
> +        mov_w r0, EARLY_UART_VIRTUAL_ADDRESS
> +        create_mapping_entry xen_fixmap, r0, r11, type=PT_DEV_L3
When building this patch, I'm getting a "Bad instruction" build error.
Quick look shows that you are trying to use the macro create_mapping_entry 
before macro definition.
Unless, I'm using a different baseline (latest staging) than you, this needs to 
be fixed.

Apart from that:
Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>

~Michal