Re: [kvm-unit-tests PATCH v3 3/7] s390x: Introduce and use CALL_INT_HANDLER macro

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Mon, 22 Feb 2021 03:57:52 -0500
Janosch Frank <frankja@linux.ibm.com> wrote:

> The ELF ABI dictates that we need to allocate 160 bytes of stack space
> for the C functions we're calling. Since we would need to do that for
> every interruption handler which, combined with the new stack argument
> being saved in GR2, makes cstart64.S look a bit messy.
> 
> So let's introduce the CALL_INT_HANDLER macro that handles all of
> that, calls the C interrupt handler and handles cleanup afterwards.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  s390x/cstart64.S | 28 +++++-----------------------
>  s390x/macros.S   | 17 +++++++++++++++++
>  2 files changed, 22 insertions(+), 23 deletions(-)
> 
> diff --git a/s390x/cstart64.S b/s390x/cstart64.S
> index 35d20293..666a9567 100644
> --- a/s390x/cstart64.S
> +++ b/s390x/cstart64.S
> @@ -92,37 +92,19 @@ memsetxc:
>  
>  .section .text
>  pgm_int:
> -	SAVE_REGS_STACK
> -	lgr     %r2, %r15
> -	brasl	%r14, handle_pgm_int
> -	RESTORE_REGS_STACK
> -	lpswe	GEN_LC_PGM_OLD_PSW
> +	CALL_INT_HANDLER handle_pgm_int, GEN_LC_PGM_OLD_PSW
>  
>  ext_int:
> -	SAVE_REGS_STACK
> -	lgr     %r2, %r15
> -	brasl	%r14, handle_ext_int
> -	RESTORE_REGS_STACK
> -	lpswe	GEN_LC_EXT_OLD_PSW
> +	CALL_INT_HANDLER handle_ext_int, GEN_LC_EXT_OLD_PSW
>  
>  mcck_int:
> -	SAVE_REGS_STACK
> -	brasl	%r14, handle_mcck_int
> -	RESTORE_REGS_STACK
> -	lpswe	GEN_LC_MCCK_OLD_PSW
> +	CALL_INT_HANDLER handle_mcck_int, GEN_LC_MCCK_OLD_PSW
>  
>  io_int:
> -	SAVE_REGS_STACK
> -	lgr     %r2, %r15
> -	brasl	%r14, handle_io_int
> -	RESTORE_REGS_STACK
> -	lpswe	GEN_LC_IO_OLD_PSW
> +	CALL_INT_HANDLER handle_io_int, GEN_LC_IO_OLD_PSW
>  
>  svc_int:
> -	SAVE_REGS_STACK
> -	brasl	%r14, handle_svc_int
> -	RESTORE_REGS_STACK
> -	lpswe	GEN_LC_SVC_OLD_PSW
> +	CALL_INT_HANDLER handle_svc_int, GEN_LC_SVC_OLD_PSW
>  
>  	.align	8
>  initial_psw:
> diff --git a/s390x/macros.S b/s390x/macros.S
> index a7d62c6f..11f4397a 100644
> --- a/s390x/macros.S
> +++ b/s390x/macros.S
> @@ -11,6 +11,23 @@
>   *  David Hildenbrand <david@redhat.com>
>   */
>  #include <asm/asm-offsets.h>
> +/*
> + * Exception handler macro that saves registers on the stack,
> + * allocates stack space and calls the C handler function. Afterwards
> + * we re-load the registers and load the old PSW.
> + */
> +	.macro CALL_INT_HANDLER c_func, old_psw
> +	SAVE_REGS_STACK
> +	/* Save the stack address in GR2 which is the first function
> argument */
> +	lgr     %r2, %r15
> +	/* Allocate stack space for called C function, as specified
> in s390 ELF ABI */
> +	slgfi   %r15, 160
> +	brasl	%r14, \c_func
> +	algfi   %r15, 160
> +	RESTORE_REGS_STACK
> +	lpswe	\old_psw
> +	.endm
> +
>  	.macro SAVE_REGS
>  	/* save grs 0-15 */
>  	stmg	%r0, %r15, GEN_LC_SW_INT_GRS