Re: [Minios-devel] [UNIKRAFT early RFC PATCH 06/11] plat/kvm: arm64: Add a parameter to start_mmu

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 21/06/2019 07:57, Jia He wrote:
> This is to bypass invalidate and clean pgtable D-cache. This is not
> required when APs are booting up.
>
> Signed-off-by: Jia He <justin.he@xxxxxxx>
> ---
>   plat/kvm/arm/entry64.S     | 1 +
>   plat/kvm/arm/pagetable64.S | 7 ++++++-
>   2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/plat/kvm/arm/entry64.S b/plat/kvm/arm/entry64.S
> index ff63ee0..df59ef6 100644
> --- a/plat/kvm/arm/entry64.S
> +++ b/plat/kvm/arm/entry64.S
> @@ -125,6 +125,7 @@ ENTRY(_libkvmplat_entry)
>         msr VBAR_EL1, x29
>   
>   	/* Enable the mmu */
> +       mov x7, #0
Please try to document as much as possible assembly code. For instance, you set 
x7 here but it is used later in a different function. The diff of the patch 
makes it clear to understand. However, if you look at the code itself then it 
becomes impossible to find.
In this context, I think it would be best if start_mmu() is split in two 
functions. The boot CPU would call the two functions, while the secondary CPU 
would only call the one.
>         bl start_mmu
>   
>   	/* Load dtb address to x0 as a parameter */
> diff --git a/plat/kvm/arm/pagetable64.S b/plat/kvm/arm/pagetable64.S
> index 7899c19..abb024f 100644
> --- a/plat/kvm/arm/pagetable64.S
> +++ b/plat/kvm/arm/pagetable64.S
> @@ -36,6 +36,8 @@
>   #include <uk/asm.h>
>   #include <kvm-arm/mm.h>
>   #include <arm/cpu_defs.h>
> +#include <uk/config.h>
> +
>   /*
>    * The following is the Memory Layout of AArch64 Virtual Machine
>    * | 0 - 0x3FFFFFFF |   0x40000000 - 0x7FFFFFFFFF           |  512GB - 1TB   |
> @@ -234,6 +236,9 @@ ENTRY(start_mmu)
>         bfi x2, x3, #32, #3
>         msr tcr_el1, x2
>   
> +	cmp x7, #1
> +       beq 1f
> +
>         /* save lr */
>         mov x22, x30
>   
> @@ -262,7 +267,7 @@ ENTRY(start_mmu)
>   
>   	/* restore lr */
>         mov x30, x22
> -
> +1:
>         ret
>   END(start_mmu)
>   
--
Julien Grall

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