Re: [PATCH v1 1/4] s390x: saving regs for interrupts

David Hildenbrand
2019-11-14T10:28:33Z

> Am 14.11.2019 um 11:11 schrieb Pierre Morel <pmorel@linux.ibm.com>:
>
> ﻿
>> On 2019-11-13 17:12, Janosch Frank wrote:
>>> On 11/13/19 1:23 PM, Pierre Morel wrote:
>>> If we use multiple source of interrupts, for exemple, using SCLP console
>>> to print information while using I/O interrupts or during exceptions, we
>>> need to have a re-entrant register saving interruption handling.
>>>
>>> Instead of saving at a static place, let's save the base registers on
>>> the stack.
>>>
>>> Note that we keep the static register saving that we need for the RESET
>>> tests.
>>>
>>> We also care to give the handlers a pointer to the save registers in
>>> case the handler needs it (fixup_pgm_int needs the old psw address).
>> So you're still ignoring the FPRs...
>> I disassembled a test and looked at all stds and it looks like printf
>> and related functions use them. Wouldn't we overwrite test FPRs if
>> printing in a handler?
>
> If printf uses the FPRs in my opinion we should modify the compilation options for the library.
>
> What is the reason for printf and related functions to use floating point?
>

Register spilling. This can and will be done.

Cheers.

> I will have a deeper look at this.
>
>
> Regards,
>
> Pierre
>
>
> --
> Pierre Morel
> IBM Lab Boeblingen
>