Re: [PATCH RFC v2 3/4] pc-bios: s390x: Save io and external new PSWs before overwriting them

[Janosch Frank]

On 8/27/20 2:52 PM, Thomas Huth wrote:
> On 27/08/2020 11.31, Janosch Frank wrote:
>> Currently we always overwrite the mentioned exception new PSWs before
>> loading the enabled wait PSW. Let's save the PSW before overwriting
>> and restore it right before starting the loaded kernel.
>>
>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>> ---
>>
>> Maybe we should rather statically allocate a lowcore so we don't dirty
>> 0x0 at all.
>>
>> ---
>>  pc-bios/s390-ccw/jump2ipl.c |  3 ++
>>  pc-bios/s390-ccw/start.S    | 62 +++++++++++++++++++++++++++----------
>>  2 files changed, 48 insertions(+), 17 deletions(-)
>>
>> diff --git a/pc-bios/s390-ccw/jump2ipl.c b/pc-bios/s390-ccw/jump2ipl.c
>> index 143d027bf7..a44f3ab5b3 100644
>> --- a/pc-bios/s390-ccw/jump2ipl.c
>> +++ b/pc-bios/s390-ccw/jump2ipl.c
>> @@ -13,12 +13,15 @@
>>  #define KERN_IMAGE_START 0x010000UL
>>  #define RESET_PSW_MASK (PSW_MASK_SHORTPSW | PSW_MASK_64)
>>  
>> +extern uint64_t *psw_save_io, *psw_save_ext;
> 
> I think that should be
> 
>  extern uint64_t psw_save_io[], psw_save_ext[];
> 
> instead ... otherwise you'll end up with some funny bugs here, won't you?

What kind of bugs are you expecting?

> 
>>  uint64_t *reset_psw = 0, save_psw, ipl_continue;
>>  
>>  static void jump_to_IPL_2(void)
>>  {
>>      /* Restore reset PSW and io and external new PSWs */
> 
> Ok, now the comment makes sense :-)
>>      *reset_psw = save_psw;
>> +    memcpy((void *)0x1f0, psw_save_io, 16);
>> +    memcpy((void *)0x1b0, psw_save_ext, 16);
> 
> Could you use &lowcore->external_new_psw and &lowcore->io_new_psw
> instead of the magic numbers?

I can, but that means that I need to declare lowcore in netmain.c as
well as including s390-arch.h

> 
>  Thomas
> 
> 
>

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