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

[Janosch Frank]

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.


> 
>> @@ -77,7 +84,12 @@ void jump_to_low_kernel(void)
>>  
>>      /* Trying to get PSW at zero address */
>>      if (*((uint64_t *)0) & RESET_PSW_MASK) {
>> -        jump_to_IPL_code((*((uint64_t *)0)) & PSW_MASK_SHORT_ADDR);
>> +        /*
>> +         * Surely nobody will try running directly from lowcore, so
>> +         * let's use 0 as an indication that we want to load the reset
>> +         * psw at 0x0 and not jump to the entry.
>> +         */
>> +        jump_to_IPL_code(0);
>>      }
>>  
>>      /* No other option left, so use the Linux kernel start address */
>> diff --git a/pc-bios/s390-ccw/s390-ccw.h b/pc-bios/s390-ccw/s390-ccw.h
>> index 36b884cced..7090720422 100644
>> --- a/pc-bios/s390-ccw/s390-ccw.h
>> +++ b/pc-bios/s390-ccw/s390-ccw.h
>> @@ -78,6 +78,7 @@ int virtio_read(ulong sector, void *load_addr);
>>  void zipl_load(void);
>>  
>>  /* jump2ipl.c */
>> +void write_reset_psw(uint64_t psw);
>>  void jump_to_IPL_code(uint64_t address);
>>  void jump_to_low_kernel(void);
> 
> Looks sane to me:
> 
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> 
>

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