Re: [kvm-unit-tests v2 PATCH] s390x: sie: Test whether the epoch extension field is working as expected

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

On Thu,  8 Dec 2022 18:05:02 +0100
Thomas Huth <thuth@redhat.com> wrote:

> We recently discovered a bug with the time management in nested scenarios
> which got fixed by kernel commit "KVM: s390: vsie: Fix the initialization
> of the epoch extension (epdx) field". This adds a simple test for this
> bug so that it is easier to determine whether the host kernel of a machine
> has already been fixed or not.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>

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

> ---
>  v2: Remove the spurious "2" from the diag 44 opcode
> 
>  s390x/sie.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/s390x/sie.c b/s390x/sie.c
> index 87575b29..cd3cea10 100644
> --- a/s390x/sie.c
> +++ b/s390x/sie.c
> @@ -58,6 +58,33 @@ static void test_diags(void)
>  	}
>  }
>  
> +static void test_epoch_ext(void)
> +{
> +	u32 instr[] = {
> +		0xb2780000,	/* STCKE 0 */
> +		0x83000044	/* DIAG 0x44 to intercept */
> +	};
> +
> +	if (!test_facility(139)) {
> +		report_skip("epdx: Multiple Epoch Facility is not available");
> +		return;
> +	}
> +
> +	guest[0] = 0x00;
> +	memcpy(guest_instr, instr, sizeof(instr));
> +
> +	vm.sblk->gpsw.addr = PAGE_SIZE * 2;
> +	vm.sblk->gpsw.mask = PSW_MASK_64;
> +
> +	vm.sblk->ecd |= ECD_MEF;
> +	vm.sblk->epdx = 0x47;	/* Setting the epoch extension here ... */
> +
> +	sie(&vm);
> +
> +	/* ... should result in the same epoch extension here: */
> +	report(guest[0] == 0x47, "epdx: different epoch is visible in the guest");
> +}
> +
>  static void setup_guest(void)
>  {
>  	setup_vm();
> @@ -80,6 +107,7 @@ int main(void)
>  
>  	setup_guest();
>  	test_diags();
> +	test_epoch_ext();
>  	sie_guest_destroy(&vm);
>  
>  done: