Re: [kvm-unit-tests PATCH v3 2/6] s390x: add function to set DAT mode for all interrupts

[Janosch Frank <frankja@linux.ibm.com>]

On 6/1/23 09:01, Nico Boehr wrote:
> When toggling DAT or switch address space modes, it is likely that

s/switch/switching/

> interrupts should be handled in the same DAT or address space mode.
> 
> Add a function which toggles DAT and address space mode for all
> interruptions, except restart interrupts.
> 
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> ---
>   lib/s390x/asm/interrupt.h |  4 ++++
>   lib/s390x/interrupt.c     | 35 +++++++++++++++++++++++++++++++++++
>   lib/s390x/mmu.c           |  5 +++--
>   3 files changed, 42 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/s390x/asm/interrupt.h b/lib/s390x/asm/interrupt.h
> index 35c1145f0349..55759002dce2 100644
> --- a/lib/s390x/asm/interrupt.h
> +++ b/lib/s390x/asm/interrupt.h
> @@ -83,6 +83,10 @@ void expect_ext_int(void);
>   uint16_t clear_pgm_int(void);
>   void check_pgm_int_code(uint16_t code);
>   
> +#define IRQ_DAT_ON	true
> +#define IRQ_DAT_OFF	false
> +void irq_set_dat_mode(bool dat, uint64_t as);
> +
>   /* Activate low-address protection */
>   static inline void low_prot_enable(void)
>   {
> diff --git a/lib/s390x/interrupt.c b/lib/s390x/interrupt.c
> index 3f993a363ae2..d97b5a3a7e97 100644
> --- a/lib/s390x/interrupt.c
> +++ b/lib/s390x/interrupt.c
> @@ -9,6 +9,7 @@
>    */
>   #include <libcflat.h>
>   #include <asm/barrier.h>
> +#include <asm/mem.h>
>   #include <asm/asm-offsets.h>
>   #include <sclp.h>
>   #include <interrupt.h>
> @@ -104,6 +105,40 @@ void register_ext_cleanup_func(void (*f)(struct stack_frame_int *))
>   	THIS_CPU->ext_cleanup_func = f;
>   }
>   
> +/**
> + * irq_set_dat_mode - Set the DAT mode of all interrupt handlers, except for
> + * restart.
> + * This will update the DAT mode and address space mode of all interrupt new
> + * PSWs.
> + *
> + * Since enabling DAT needs initalized CRs and the restart new PSW is often used

s/initalized/initialized/

That seems to be a problematic word.

> + * to initalize CRs, the restart new PSW is never touched to avoid the chicken
> + * and egg situation.

Same here.

> + *
> + * @dat specifies whether to use DAT or not
> + * @as specifies the address space mode to use - one of AS_PRIM, AS_ACCR,
> + * AS_SECN or AS_HOME.
> + */
> +void irq_set_dat_mode(bool dat, uint64_t as)
> +{
> +	struct psw* irq_psws[] = {
> +		OPAQUE_PTR(GEN_LC_EXT_NEW_PSW),
> +		OPAQUE_PTR(GEN_LC_SVC_NEW_PSW),
> +		OPAQUE_PTR(GEN_LC_PGM_NEW_PSW),
> +		OPAQUE_PTR(GEN_LC_MCCK_NEW_PSW),
> +		OPAQUE_PTR(GEN_LC_IO_NEW_PSW),
> +		NULL /* sentinel */
> +	};
> +
> +	assert(as == AS_PRIM || as == AS_ACCR || as == AS_SECN || as == AS_HOME);

/* There are only 4 spaces */
assert(as < 4); ?

> +
> +	for (struct psw *psw = irq_psws[0]; psw != NULL; psw++) {

While this is ok in gnu99/c99 I generally prefer declaring the variable 
outside of the loop since it's more readable when using structs and unions.

> +		psw->dat = dat;
> +		if (dat)
> +			psw->as = as;

Does that check even matter?

> +	}
> +}
> +
>   static void fixup_pgm_int(struct stack_frame_int *stack)
>   {
>   	/* If we have an error on SIE we directly move to sie_exit */
> diff --git a/lib/s390x/mmu.c b/lib/s390x/mmu.c
> index b474d7021d3f..199bd3fbc9c8 100644
> --- a/lib/s390x/mmu.c
> +++ b/lib/s390x/mmu.c
> @@ -12,6 +12,7 @@
>   #include <asm/pgtable.h>
>   #include <asm/arch_def.h>
>   #include <asm/barrier.h>
> +#include <asm/interrupt.h>
>   #include <vmalloc.h>
>   #include "mmu.h"
>   
> @@ -41,8 +42,8 @@ static void mmu_enable(pgd_t *pgtable)
>   	/* enable dat (primary == 0 set as default) */
>   	enable_dat();
>   
> -	/* we can now also use DAT unconditionally in our PGM handler */
> -	lowcore.pgm_new_psw.mask |= PSW_MASK_DAT;
> +	/* we can now also use DAT in all interrupt handlers */
> +	irq_set_dat_mode(IRQ_DAT_ON, AS_PRIM);
>   }
>   
>   /*