[PATCH] xen/arm64: Use virtual address when setting up early_printk fixmap

[PATCH] xen/arm64: Use virtual address when setting up early_printk fixmap

[Chen Baozi]

From: Chen Baozi <baozich@gmail.com>

We have already had the boot pagetable when reaching the point
of early_printk fixmap setup. Thus there is no longer necessary
to caculate physical address of xen_fixmap.

Signed-off-by: Chen Baozi <baozich@gmail.com>
---
 xen/arch/arm/arm64/head.S | 1 -
 1 file changed, 1 deletion(-)

diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 75b7ee1..a2ac2d4 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -520,7 +520,6 @@ paging:
 
         /* Add UART to the fixmap table */
         ldr   x1, =xen_fixmap
-        add   x1, x1, x20            /* x1 := paddr (xen_fixmap) */
         lsr   x2, x23, #THIRD_SHIFT
         lsl   x2, x2, #THIRD_SHIFT   /* 4K aligned paddr of UART */
         mov   x3, #PT_DEV_L3
-- 
2.1.4

Re: [PATCH] xen/arm64: Use virtual address when setting up early_printk fixmap

[Julien Grall]

Hi Chen,

On 07/04/2015 08:33, Chen Baozi wrote:
> From: Chen Baozi <baozich@gmail.com>
>
> We have already had the boot pagetable when reaching the point
> of early_printk fixmap setup. Thus there is no longer necessary
> to caculate physical address of xen_fixmap.

s/caculate/calculate/


OOI, is it a bug or a clean up?

>
> Signed-off-by: Chen Baozi <baozich@gmail.com>
> ---
>   xen/arch/arm/arm64/head.S | 1 -
>   1 file changed, 1 deletion(-)
>
> diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
> index 75b7ee1..a2ac2d4 100644
> --- a/xen/arch/arm/arm64/head.S
> +++ b/xen/arch/arm/arm64/head.S
> @@ -520,7 +520,6 @@ paging:
>
>           /* Add UART to the fixmap table */
>           ldr   x1, =xen_fixmap
> -        add   x1, x1, x20            /* x1 := paddr (xen_fixmap) */

You need to add a comment on "ldr x1..." in order to explain what x1 
contains. i.e /* x1 := vaddr (xen_fixmap) */

Regards,

-- 
Julien Grall

Re: [PATCH] xen/arm64: Use virtual address when setting up early_printk fixmap

[Chen Baozi]

On Tue, Apr 07, 2015 at 12:07:28PM +0100, Julien Grall wrote:
> Hi Chen,
> 
> On 07/04/2015 08:33, Chen Baozi wrote:
> >From: Chen Baozi <baozich@gmail.com>
> >
> >We have already had the boot pagetable when reaching the point
> >of early_printk fixmap setup. Thus there is no longer necessary
> >to caculate physical address of xen_fixmap.
> 
> s/caculate/calculate/
> 

Oops, ;-)

> 
> OOI, is it a bug or a clean up?

I think it should be a clean up. There is 1:1 mapping at early stage.
So it is all right to access the 'physical' address.

> 
> >
> >Signed-off-by: Chen Baozi <baozich@gmail.com>
> >---
> >  xen/arch/arm/arm64/head.S | 1 -
> >  1 file changed, 1 deletion(-)
> >
> >diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
> >index 75b7ee1..a2ac2d4 100644
> >--- a/xen/arch/arm/arm64/head.S
> >+++ b/xen/arch/arm/arm64/head.S
> >@@ -520,7 +520,6 @@ paging:
> >
> >          /* Add UART to the fixmap table */
> >          ldr   x1, =xen_fixmap
> >-        add   x1, x1, x20            /* x1 := paddr (xen_fixmap) */
> 
> You need to add a comment on "ldr x1..." in order to explain what x1
> contains. i.e /* x1 := vaddr (xen_fixmap) */

Ok. I'll add it in V2.

Cheers,

Baozi.