Re: [PATCH v3 3/5] pc-bios: s390x: Use reset PSW if avaliable

[Thomas Huth <thuth@redhat.com>]

On 02/09/2020 10.46, Janosch Frank wrote:
> On 9/1/20 6:59 PM, Thomas Huth wrote:
>> On 31/08/2020 17.09, Janosch Frank wrote:
>>> If a blob provides a reset PSW then we should use it instead of
>>> branching to the PSW address and using our own mask.
>>>
>>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>>> ---
>>>  pc-bios/s390-ccw/bootmap.c  |  3 ++-
>>>  pc-bios/s390-ccw/jump2ipl.c | 22 +++++++++++++++++-----
>>>  pc-bios/s390-ccw/s390-ccw.h |  1 +
>>>  3 files changed, 20 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/pc-bios/s390-ccw/bootmap.c b/pc-bios/s390-ccw/bootmap.c
>>> index 8747c4ea26..5a03b1eb8b 100644
>>> --- a/pc-bios/s390-ccw/bootmap.c
>>> +++ b/pc-bios/s390-ccw/bootmap.c
>>> @@ -515,7 +515,8 @@ static void zipl_run(ScsiBlockPtr *pte)
>>>      IPL_assert(entry->component_type == ZIPL_COMP_ENTRY_EXEC, "No EXEC entry");
>>>  
>>>      /* should not return */
>>> -    jump_to_IPL_code(entry->compdat.load_psw & PSW_MASK_SHORT_ADDR);
>>> +    write_reset_psw(entry->compdat.load_psw);
>>> +    jump_to_IPL_code(0);
>>>  }
>>>  
>>>  static void ipl_scsi(void)
>>> diff --git a/pc-bios/s390-ccw/jump2ipl.c b/pc-bios/s390-ccw/jump2ipl.c
>>> index b6aad32def..5b8352d257 100644
>>> --- a/pc-bios/s390-ccw/jump2ipl.c
>>> +++ b/pc-bios/s390-ccw/jump2ipl.c
>>> @@ -12,15 +12,21 @@
>>>  
>>>  #define KERN_IMAGE_START 0x010000UL
>>>  #define RESET_PSW_MASK (PSW_MASK_SHORTPSW | PSW_MASK_64)
>>> +#define RESET_PSW ((uint64_t)&jump_to_IPL_addr | RESET_PSW_MASK)
>>>  
>>>  static uint64_t *reset_psw = 0, save_psw, ipl_continue;
>>>  
>>> +void write_reset_psw(uint64_t psw)
>>> +{
>>> +    *reset_psw = psw;
>>> +}
>>> +
>>>  static void jump_to_IPL_addr(void)
>>>  {
>>>      __attribute__((noreturn)) void (*ipl)(void) = (void *)ipl_continue;
>>>  
>>>      /* Restore reset PSW */
>>> -    *reset_psw = save_psw;
>>> +    write_reset_psw(save_psw);
>>>  
>>>      ipl();
>>>      /* should not return */
>>> @@ -43,9 +49,10 @@ 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.
>>>       */
>>> -    save_psw = *reset_psw;
>>> -    *reset_psw = (uint64_t) &jump_to_IPL_addr;
>>> -    *reset_psw |= RESET_PSW_MASK;
>>> +    if (address) {
>>> +        save_psw = *reset_psw;
>>> +        write_reset_psw(RESET_PSW);
>>> +    }
>>>      ipl_continue = address;
>>>      debug_print_int("set IPL addr to", ipl_continue);
>>
>> In case you respin this series, I think I'd move the "ipl_continue =
>> address" into the if-statement, too, and change the debug_print_int line
>> to use address instead of ipl_continue.
> 
> Hmm, my intention was to always have something printed.
> But I guess it would make more sense to print the reset psw addr in the
> ~address case.

I meant to only move the "ipl_continue = address" line and keep the
debug_print_int() at its current place (you just have to replace
ipl_continue there). But you're right, it would make more sense to print
the PSW at address 0 in that case instead.

 Thomas