Re: [PATCH v1 3/8] xen/riscv: introduce stack stuff

[Julien Grall <julien@xen.org>]

Hi,

On 06/01/2023 13:14, Oleksii Kurochko wrote:
> The patch introduces and sets up a stack in order to go to C environment
> 
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
> ---
>   xen/arch/riscv/Makefile       | 1 +
>   xen/arch/riscv/riscv64/head.S | 8 +++++++-
>   xen/arch/riscv/setup.c        | 6 ++++++
>   3 files changed, 14 insertions(+), 1 deletion(-)
>   create mode 100644 xen/arch/riscv/setup.c
> 
> diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
> index 248f2cbb3e..5a67a3f493 100644
> --- a/xen/arch/riscv/Makefile
> +++ b/xen/arch/riscv/Makefile
> @@ -1,4 +1,5 @@
>   obj-$(CONFIG_RISCV_64) += riscv64/
> +obj-y += setup.o
>   
>   $(TARGET): $(TARGET)-syms
>   	$(OBJCOPY) -O binary -S $< $@
> diff --git a/xen/arch/riscv/riscv64/head.S b/xen/arch/riscv/riscv64/head.S
> index 990edb70a0..ddc7104701 100644
> --- a/xen/arch/riscv/riscv64/head.S
> +++ b/xen/arch/riscv/riscv64/head.S
> @@ -1,4 +1,10 @@
>           .section .text.header, "ax", %progbits
>   
>   ENTRY(start)
> -        j  start
> +        la      sp, cpu0_boot_stack
> +        li      t0, PAGE_SIZE

I would recommend to a define STACK_SIZE. So you don't make assumption 
on the size in the code and it is easier to update.

> +        add     sp, sp, t0
> +
> +_start_hang:
> +        wfi
> +        j  _start_hang
> diff --git a/xen/arch/riscv/setup.c b/xen/arch/riscv/setup.c
> new file mode 100644
> index 0000000000..2c7dca1daa
> --- /dev/null
> +++ b/xen/arch/riscv/setup.c
> @@ -0,0 +1,6 @@
> +#include <xen/init.h>
> +#include <xen/compile.h>
> +
> +/* Xen stack for bringing up the first CPU. */
> +unsigned char __initdata cpu0_boot_stack[PAGE_SIZE]
> +    __aligned(PAGE_SIZE);

Cheers,

-- 
Julien Grall