Re: [Qemu-devel] [qemu-s390x] [PATCH v4 1/1] s390x/ipl: Try to detect Linux vs non Linux for initial IPL PSW

[Thomas Huth <thuth@redhat.com>]

On 12.06.2018 14:59, Christian Borntraeger wrote:
> Right now the IPL device always starts from address 0x10000 (the usual
> Linux entry point). To run other guests (e.g. test programs) it is
> useful to use the IPL PSW from address 0. We can use the Linux magic
> at 0x10008 to decide.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
> v3->v4:
> 	- iplpsw-> ipl_psw
> 	- move check for load failures into the non-elf case
> 	- change comment about ipl psw
> v2->v3:
> 	- check for iplpsw to avoid assert on file errors
> 	- use 4 bytes at 4 instead of 8 bytes at 0
> v1->v2:
> 	- use LINUX_MAGIC_ADDR define
> 	- use assert for valid iplpsw pointer
> 	- add endianess conversion
>  hw/s390x/ipl.c | 27 ++++++++++++++++++++++-----
>  1 file changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
> index 04245b5258..0d67349004 100644
> --- a/hw/s390x/ipl.c
> +++ b/hw/s390x/ipl.c
> @@ -29,6 +29,7 @@
>  #include "exec/exec-all.h"
>  
>  #define KERN_IMAGE_START                0x010000UL
> +#define LINUX_MAGIC_ADDR                0x010008UL
>  #define KERN_PARM_AREA                  0x010480UL
>  #define INITRD_START                    0x800000UL
>  #define INITRD_PARM_START               0x010408UL
> @@ -105,7 +106,9 @@ static uint64_t bios_translate_addr(void *opaque, uint64_t srcaddr)
>  static void s390_ipl_realize(DeviceState *dev, Error **errp)
>  {
>      S390IPLState *ipl = S390_IPL(dev);
> -    uint64_t pentry = KERN_IMAGE_START;
> +    uint32_t *ipl_psw;
> +    uint64_t pentry;
> +    char *magic;
>      int kernel_size;
>      Error *err = NULL;
>  
> @@ -157,10 +160,24 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp)
>                                 NULL, 1, EM_S390, 0, 0);
>          if (kernel_size < 0) {
>              kernel_size = load_image_targphys(ipl->kernel, 0, ram_size);
> -        }
> -        if (kernel_size < 0) {
> -            error_setg(&err, "could not load kernel '%s'", ipl->kernel);
> -            goto error;
> +            if (kernel_size < 0) {
> +                error_setg(&err, "could not load kernel '%s'", ipl->kernel);
> +                goto error;
> +            }
> +            /* if this is Linux use KERN_IMAGE_START */
> +            magic = rom_ptr(LINUX_MAGIC_ADDR);
> +            if (magic && !memcmp(magic, "S390EP", 6)) {
> +                pentry = KERN_IMAGE_START;
> +            } else {
> +                /* if not Linux load the address of the (short) IPL PSW */
> +                ipl_psw = rom_ptr(4);
> +                if (ipl_psw) {
> +                    pentry = be32_to_cpu(*ipl_psw) & 0x7fffffffUL;
> +                } else {
> +                    error_setg(&err, "Could not get IPL PSW");
> +                    goto error;
> +                }
> +            }
>          }
>          /*
>           * Is it a Linux kernel (starting at 0x10000)? If yes, we fill in the
> 

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