Re: [Qemu-devel] [PATCH v2 1/1] s390x/ipl: Try to detect Linux vs non Linux for initial IPL PSW

[David Hildenbrand <david@redhat.com>]

On 11.06.2018 18:11, Thomas Huth wrote:
> On 11.06.2018 15:56, David Hildenbrand wrote:
>> On 11.06.2018 15:52, 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>
>>> ---
>>> v1->v2:
>>> 	- use LINUX_MAGIC_ADDR define
>>> 	- use assert for valid iplpsw pointer
>>> 	- add endianess conversion
>>>  hw/s390x/ipl.c | 15 ++++++++++++++-
>>>  1 file changed, 14 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
>>> index 04245b5258..3790153fa9 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;
>>> +    uint64_t *iplpsw;
>>> +    uint64_t pentry;
>>> +    char *magic;
>>>      int kernel_size;
>>>      Error *err = NULL;
>>>  
>>> @@ -157,6 +160,16 @@ 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 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 use the IPL PSW */
>>> +                iplpsw = rom_ptr(0);
>>> +                assert(iplpsw);
>>> +                pentry = be64_to_cpu(*iplpsw) & 0x7fffffffUL;
>>> +            }
>>>          }
>>>          if (kernel_size < 0) {
>>>              error_setg(&err, "could not load kernel '%s'", ipl->kernel);
>>>
>>
>> Have you tried this with kvm-unit-tests? (no magic but we rely on 0x10000)
> 
> kvm-unit-tests are elf files which should be handled by the load_elf()
> some lines earlier already, so I think we should be fine there,
> shouldn't we?

Indeed, this should work.

> 
>  Thomas
> 
> 


-- 

Thanks,

David / dhildenb