Re: [PATCH v3 2/5] pc-bios: s390x: Save PSW rework

[Thomas Huth]

On 31/08/2020 17.09, Janosch Frank wrote:
> We don't need to save the ipl_continue variable in lowcore and have it
> limited to 32 bits because of the lowcore layout. Let's move it to a
> new 64 bit variable and get rid of the reset info struct.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
>  pc-bios/s390-ccw/jump2ipl.c | 33 +++++++++++++--------------------
>  1 file changed, 13 insertions(+), 20 deletions(-)
> 
> diff --git a/pc-bios/s390-ccw/jump2ipl.c b/pc-bios/s390-ccw/jump2ipl.c
> index 767012bf0c..b6aad32def 100644
> --- a/pc-bios/s390-ccw/jump2ipl.c
> +++ b/pc-bios/s390-ccw/jump2ipl.c
> @@ -13,20 +13,17 @@
>  #define KERN_IMAGE_START 0x010000UL
>  #define RESET_PSW_MASK (PSW_MASK_SHORTPSW | PSW_MASK_64)
>  
> -typedef struct ResetInfo {
> -    uint64_t ipl_psw;
> -    uint32_t ipl_continue;
> -} ResetInfo;
> +static uint64_t *reset_psw = 0, save_psw, ipl_continue;
>  
> -static ResetInfo save;
> -
> -static void jump_to_IPL_2(void)
> +static void jump_to_IPL_addr(void)
>  {
> -    ResetInfo *current = 0;
> +    __attribute__((noreturn)) void (*ipl)(void) = (void *)ipl_continue;
>  
> -    void (*ipl)(void) = (void *) (uint64_t) current->ipl_continue;
> -    *current = save;
> -    ipl(); /* should not return */
> +    /* Restore reset PSW */
> +    *reset_psw = save_psw;
> +
> +    ipl();
> +    /* should not return */
>  }
>  
>  void jump_to_IPL_code(uint64_t address)
> @@ -46,15 +43,11 @@ void jump_to_IPL_code(uint64_t address)
>       * content of non-BIOS memory after we loaded the guest, so we
>       * save the original content and restore it in jump_to_IPL_2.
>       */
> -    ResetInfo *current = 0;
> -
> -    save = *current;
> -
> -    current->ipl_psw = (uint64_t) &jump_to_IPL_2;
> -    current->ipl_psw |= RESET_PSW_MASK;
> -    current->ipl_continue = address & PSW_MASK_SHORT_ADDR;
> -
> -    debug_print_int("set IPL addr to", current->ipl_continue);
> +    save_psw = *reset_psw;
> +    *reset_psw = (uint64_t) &jump_to_IPL_addr;
> +    *reset_psw |= RESET_PSW_MASK;
> +    ipl_continue = address;
> +    debug_print_int("set IPL addr to", ipl_continue);
>  
>      /* Ensure the guest output starts fresh */
>      sclp_print("\n");

Reviewed-by: Thomas Huth <thuth@redhat.com>