Re: [qemu-s390x] [kvm-unit-tests PATCH 1/5] s390x: Make tests bootable from disk

[Janosch Frank]

On 04.12.18 15:06, David Hildenbrand wrote:
> On 04.12.18 14:58, Janosch Frank wrote:
>> On 04.12.18 14:52, David Hildenbrand wrote:
>>> On 04.12.18 14:48, Janosch Frank wrote:
>>>> Currently tests are run with the --kernel option of Qemu, which will
>>>> load the ELF file and jump to the start address. When booting from
>>>> disk, we need to specify a start address. This is done by setting the
>>>> initial short PSW at 0x0.
>>>>
>>>> For later compatibility with other hypervisors the short psw has 31
>>>> bit addressing specified.
>>>>
>>>> Signed-off-by: Janosch Frank <address@hidden>
>>>> ---
>>>>  s390x/cstart64.S | 9 +++++++--
>>>>  s390x/flat.lds   | 8 +++++++-
>>>>  2 files changed, 14 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/s390x/cstart64.S b/s390x/cstart64.S
>>>> index dc7ddd6..abd6b58 100644
>>>> --- a/s390x/cstart64.S
>>>> +++ b/s390x/cstart64.S
>>>> @@ -14,12 +14,17 @@
>>>>  
>>>>  .section .init
>>>>  
>>>> -/* entry point - for KVM + TCG we directly start in 64 bit mode */
>>>> +/*
>>>> + * Short init between 0x10000 and 0x10480 and then jump to 0x11000.
>>>> + * 0x10480 - 0x11000 are written to by bootloader.
>>>> + */
>>>>    .globl start
>>>>  start:
>>>> +  sam64                           # Set addressing mode to 64 bit
>>>
>>> I guess this was supposed to go into patch #2?
>>
>> No, the short PSW has only BA set because we want to boot on lpar and
>> zvm  later on and they start with esam, not esame.
>>
>> So when booting from disk we need to sam64, as we'll run with 31 at this
>> point in time.
> 
> Please add that to the description (and remove it from the description
> of patch #2). Thanks!
> 

Sure, I'll also try to add some more comments to the assembly.

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