Re: [kvm-unit-tests PATCH v3 2/7] s390x: Fully commit to stack save area for exceptions

Thomas Huth
2021-03-04T11:40:31Z

On 22/02/2021 09.57, Janosch Frank wrote:
> Having two sets of macros for saving registers on exceptions makes
> maintaining harder. Also we have limited space in the lowcore to save
> stuff and by using the stack as a save area, we can stack exceptions.
>
> So let's use the SAVE/RESTORE_REGS_STACK as the default. When we also
> move the diag308 macro over we can remove the old SAVE/RESTORE_REGS
> macros.
>
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
[...]
> diff --git a/lib/s390x/asm/interrupt.h b/lib/s390x/asm/interrupt.h
> index 1a2e2cd8..31e4766d 100644
> --- a/lib/s390x/asm/interrupt.h
> +++ b/lib/s390x/asm/interrupt.h
> @@ -14,8 +14,8 @@
> #define EXT_IRQ_SERVICE_SIG 0x2401
>
> void register_pgm_cleanup_func(void (*f)(void));
> -void handle_pgm_int(void);
> -void handle_ext_int(void);
> +void handle_pgm_int(struct stack_frame_int *stack);
> +void handle_ext_int(struct stack_frame_int *stack);
> void handle_mcck_int(void);
> void handle_io_int(void);

So handle_io_int() does not get a *stack parameter here...

> void handle_svc_int(void);
> diff --git a/lib/s390x/interrupt.c b/lib/s390x/interrupt.c
> index 1ce36073..a59df80e 100644
> --- a/lib/s390x/interrupt.c
> +++ b/lib/s390x/interrupt.c
> @@ -56,7 +56,7 @@ void register_pgm_cleanup_func(void (*f)(void))
> pgm_cleanup_func = f;
> }
>
> -static void fixup_pgm_int(void)
> +static void fixup_pgm_int(struct stack_frame_int *stack)
> {
> /* If we have an error on SIE we directly move to sie_exit */
> if (lc->pgm_old_psw.addr >= (uint64_t)&sie_entry &&
> @@ -76,7 +76,7 @@ static void fixup_pgm_int(void)
> /* Handling for iep.c test case. */
> if (lc->trans_exc_id & 0x80UL && lc->trans_exc_id & 0x04UL &&
> !(lc->trans_exc_id & 0x08UL))
> - lc->pgm_old_psw.addr = lc->sw_int_grs[14];
> + lc->pgm_old_psw.addr = stack->grs0[12];

I'd maybe put a "/* GR14 */" comment at the end of the line, to make it more
obvious which register we're aiming here at.

> break;
> case PGM_INT_CODE_SEGMENT_TRANSLATION:
> case PGM_INT_CODE_PAGE_TRANSLATION:
> @@ -115,7 +115,7 @@ static void fixup_pgm_int(void)
> /* suppressed/terminated/completed point already at the next address */
> }
>
> -void handle_pgm_int(void)
> +void handle_pgm_int(struct stack_frame_int *stack)
> {
> if (!pgm_int_expected) {
> /* Force sclp_busy to false, otherwise we will loop forever */
> @@ -130,10 +130,10 @@ void handle_pgm_int(void)
> if (pgm_cleanup_func)
> (*pgm_cleanup_func)();
> else
> - fixup_pgm_int();
> + fixup_pgm_int(stack);
> }
>
> -void handle_ext_int(void)
> +void handle_ext_int(struct stack_frame_int *stack)
> {
> if (!ext_int_expected &&
> lc->ext_int_code != EXT_IRQ_SERVICE_SIG) {
> @@ -143,13 +143,13 @@ void handle_ext_int(void)
> }
>
> if (lc->ext_int_code == EXT_IRQ_SERVICE_SIG) {
> - lc->sw_int_crs[0] &= ~(1UL << 9);
> + stack->crs[0] &= ~(1UL << 9);
> sclp_handle_ext();
> } else {
> ext_int_expected = false;
> }
>
> - if (!(lc->sw_int_crs[0] & CR0_EXTM_MASK))
> + if (!(stack->crs[0] & CR0_EXTM_MASK))
> lc->ext_old_psw.mask &= ~PSW_MASK_EXT;
> }
>
> diff --git a/s390x/cstart64.S b/s390x/cstart64.S
> index ace0c0d9..35d20293 100644
> --- a/s390x/cstart64.S
> +++ b/s390x/cstart64.S
> @@ -92,33 +92,36 @@ memsetxc:
>
> .section .text
> pgm_int:
> - SAVE_REGS
> + SAVE_REGS_STACK
> + lgr %r2, %r15
> brasl %r14, handle_pgm_int
> - RESTORE_REGS
> + RESTORE_REGS_STACK
> lpswe GEN_LC_PGM_OLD_PSW
>
> ext_int:
> - SAVE_REGS
> + SAVE_REGS_STACK
> + lgr %r2, %r15
> brasl %r14, handle_ext_int
> - RESTORE_REGS
> + RESTORE_REGS_STACK
> lpswe GEN_LC_EXT_OLD_PSW
>
> mcck_int:
> - SAVE_REGS
> + SAVE_REGS_STACK
> brasl %r14, handle_mcck_int
> - RESTORE_REGS
> + RESTORE_REGS_STACK
> lpswe GEN_LC_MCCK_OLD_PSW
>
> io_int:
> SAVE_REGS_STACK
> + lgr %r2, %r15

... and here you're passing the stack pointer as a parameter, though
handle_io_int() does not use it... well, ok, it gets reworked again in the
next patch, but maybe you could still remove the above line when picking up
the patch?

Anyway:
Acked-by: Thomas Huth <thuth@redhat.com>