[kvm-unit-tests PATCH v5 12/29] powerpc/sprs: Avoid taking async interrupts caused by register fuzzing

[Thomas Huth]

On 16/12/2023 14.42, Nicholas Piggin wrote:
> Storing certain values in some registers can cause asynchronous
> interrupts that can crash the test case, for example decrementer
> or PMU interrupts.
> 
> Change the msleep to mdelay which does not enable MSR[EE] and so
> avoids the problem. This allows removing some of the SPR special
> casing.
> 
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> ---
>   powerpc/sprs.c | 14 ++------------
>   1 file changed, 2 insertions(+), 12 deletions(-)
> 
> diff --git a/powerpc/sprs.c b/powerpc/sprs.c
> index 01041912..313698e0 100644
> --- a/powerpc/sprs.c
> +++ b/powerpc/sprs.c
> @@ -481,12 +481,7 @@ static void set_sprs(uint64_t val)
>   			continue;
>   		if (sprs[i].type & SPR_HARNESS)
>   			continue;
> -		if (!strcmp(sprs[i].name, "MMCR0")) {
> -			/* XXX: could use a comment or better abstraction! */
> -			__mtspr(i, (val & 0xfffffffffbab3fffULL) | 0xfa0b2070);
> -		} else {
> -			__mtspr(i, val);
> -		}
> +		__mtspr(i, val);
>   	}
>   }
>   
> @@ -536,12 +531,7 @@ int main(int argc, char **argv)
>   	if (pause) {
>   		migrate_once();
>   	} else {
> -		msleep(2000);
> -
> -		/* Taking a dec updates SRR0, SRR1, SPRG1, so don't fail. */
> -		sprs[26].type |= SPR_ASYNC;
> -		sprs[27].type |= SPR_ASYNC;
> -		sprs[273].type |= SPR_ASYNC;
> +		mdelay(2000);
>   	}

IIRC I used the H_CEDE stuff here on purpose to increase the possibility 
that the guest gets rescheduled onto another CPU core on the host, and thus 
that it uncovers sprs that are not saved and restored on the host more 
easily. So I'd rather keep the msleep() here.

  Thomas