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Re: [PATCH 1/2] xen/arm32: head: Rework how the fixmap and early UART mapping are prepared
- To: Julien Grall <julien@xxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Thu, 2 Nov 2023 02:29:57 +0000
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- Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>, Julien Grall <jgrall@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Thu, 02 Nov 2023 02:30:39 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [PATCH 1/2] xen/arm32: head: Rework how the fixmap and early UART mapping are prepared
Hi Julien,
> On Nov 2, 2023, at 07:30, Julien Grall <julien@xxxxxxx> 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
I tried to test this series today and found a corner case in this patch:
If we build Xen only with this patch, and CONFIG_EARLY_PRINTK=y, we
will get below from compiler:
```
arch/arm/arm32/head.S: Assembler messages:
arch/arm/arm32/head.S:189: Error: bad instruction `create_mapping_entry
xen_fixmap,r0,r11,type=0xe73'
make[3]: *** [Rules.mk:253: arch/arm/arm32/head.o] Error 1
```
With the second patch applied, the above error will disappear and I confirm
arm32 will work fine with both patch applied + either CONFIG_EARLY_PRINTK={y,n}.
Kind regards,
Henry
|
