Re: [kvm-unit-tests PATCH v3 2/3] s390x: skey.c: rework the interrupt handler

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

On 7/13/22 12:45, Claudio Imbrenda wrote:
> The skey test currently uses a cleanup function to work around the
> issues that arise when the lowcore is not mapped, since the interrupt
> handler needs to access it.
> 
> Instead of a cleanup function, simply disable DAT for the interrupt
> handler for the tests that remap page 0. This is needed in preparation
> of and upcoming patch that will cause the interrupt handler to read
> from lowcore before calling the cleanup function.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

Acked-by: Janosch Frank <frankja@linux.ibm.com>

> ---
>   s390x/skey.c | 23 ++++++++---------------
>   1 file changed, 8 insertions(+), 15 deletions(-)
> 
> diff --git a/s390x/skey.c b/s390x/skey.c
> index 445476a0..d2752328 100644
> --- a/s390x/skey.c
> +++ b/s390x/skey.c
> @@ -250,19 +250,6 @@ static void set_prefix_key_1(uint32_t *prefix_ptr)
>   	);
>   }
>   
> -/*
> - * We remapped page 0, making the lowcore inaccessible, which breaks the normal
> - * handler and breaks skipping the faulting instruction.
> - * Just disable dynamic address translation to make things work.
> - */
> -static void dat_fixup_pgm_int(void)
> -{
> -	uint64_t psw_mask = extract_psw_mask();
> -
> -	psw_mask &= ~PSW_MASK_DAT;
> -	load_psw_mask(psw_mask);
> -}
> -
>   #define PREFIX_AREA_SIZE (PAGE_SIZE * 2)
>   static char lowcore_tmp[PREFIX_AREA_SIZE] __attribute__((aligned(PREFIX_AREA_SIZE)));
>   
> @@ -318,7 +305,13 @@ static void test_set_prefix(void)
>   	report(get_prefix() == old_prefix, "did not set prefix");
>   	report_prefix_pop();
>   
> -	register_pgm_cleanup_func(dat_fixup_pgm_int);
> +	/*
> +	 * Page 0 will be remapped, making the lowcore inaccessible, which
> +	 * breaks the normal handler and breaks skipping the faulting
> +	 * instruction. Disable dynamic address translation for the
> +	 * interrupt handler to make things work.
> +	 */
> +	lowcore.pgm_new_psw.mask &= ~PSW_MASK_DAT;
>   
>   	report_prefix_push("remapped page, fetch protection");
>   	set_prefix(old_prefix);
> @@ -356,7 +349,7 @@ static void test_set_prefix(void)
>   	report_prefix_pop();
>   
>   	ctl_clear_bit(0, CTL0_FETCH_PROTECTION_OVERRIDE);
> -	register_pgm_cleanup_func(NULL);
> +	lowcore.pgm_new_psw.mask |= PSW_MASK_DAT;
>   	report_prefix_pop();
>   	set_storage_key(pagebuf, 0x00, 0);
>   	report_prefix_pop();