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

[Julien Grall <julien@xxxxxxx>]

Hi Michal,

On 02/11/2023 09:29, Michal Orzel wrote:
> 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.
You are using the correct baseline. I have just ended up fix the build 
in patch #2 by mistake. I will move the change here.
> Apart from that:
> Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
Thanks!

Cheers,

--
Julien Grall