Re: [PATCH v3 3/6] xen/riscv: introduce stack stuff

[Alistair Francis <alistair23@xxxxxxxxx>]

On Wed, Jan 11, 2023 at 1:18 AM Oleksii Kurochko
<oleksii.kurochko@xxxxxxxxx> wrote:
>
> The patch introduces and sets up a stack in order to go to C environment
>
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>

Reviewed-by: Alistair Francis <alistair.francis@xxxxxxx>

Alistair

> ---
> Changes in V3:
>     - reorder headers in alphabetical order
>     - merge changes related to start_xen() function from "[PATCH v2 7/8]
>       xen/riscv: print hello message from C env" to this patch
>     - remove unneeded parentheses in definition of STACK_SIZE
> ---
> Changes in V2:
>     - introduce STACK_SIZE define.
>     - use consistent padding between instruction mnemonic and operand(s)
> ---
>  xen/arch/riscv/Makefile             |  1 +
>  xen/arch/riscv/include/asm/config.h |  2 ++
>  xen/arch/riscv/riscv64/head.S       |  6 +++++-
>  xen/arch/riscv/setup.c              | 14 ++++++++++++++
>  4 files changed, 22 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/include/asm/config.h 
> b/xen/arch/riscv/include/asm/config.h
> index 0370f865f3..763a922a04 100644
> --- a/xen/arch/riscv/include/asm/config.h
> +++ b/xen/arch/riscv/include/asm/config.h
> @@ -43,6 +43,8 @@
>
>  #define SMP_CACHE_BYTES (1 << 6)
>
> +#define STACK_SIZE PAGE_SIZE
> +
>  #endif /* __RISCV_CONFIG_H__ */
>  /*
>   * Local variables:
> diff --git a/xen/arch/riscv/riscv64/head.S b/xen/arch/riscv/riscv64/head.S
> index 990edb70a0..d444dd8aad 100644
> --- a/xen/arch/riscv/riscv64/head.S
> +++ b/xen/arch/riscv/riscv64/head.S
> @@ -1,4 +1,8 @@
>          .section .text.header, "ax", %progbits
>
>  ENTRY(start)
> -        j  start
> +        la      sp, cpu0_boot_stack
> +        li      t0, STACK_SIZE
> +        add     sp, sp, t0
> +
> +        tail    start_xen
> diff --git a/xen/arch/riscv/setup.c b/xen/arch/riscv/setup.c
> new file mode 100644
> index 0000000000..13e24e2fe1
> --- /dev/null
> +++ b/xen/arch/riscv/setup.c
> @@ -0,0 +1,14 @@
> +#include <xen/compile.h>
> +#include <xen/init.h>
> +
> +/* Xen stack for bringing up the first CPU. */
> +unsigned char __initdata cpu0_boot_stack[STACK_SIZE]
> +    __aligned(STACK_SIZE);
> +
> +void __init noreturn start_xen(void)
> +{
> +    for ( ;; )
> +        asm volatile ("wfi");
> +
> +    unreachable();
> +}
> --
> 2.38.1
>
>