Re: [PATCH] s390: fix detection of vector enhancements facility 1 vs. vector packed decimal facility

[Christian Borntraeger]

On 03.05.21 14:12, David Hildenbrand wrote:
> The PoP documents:
> 	134: The vector packed decimal facility is installed in the
> 	     z/Architecture architectural mode. When bit 134 is
> 	     one, bit 129 is also one.
> 	135: The vector enhancements facility 1 is installed in
> 	     the z/Architecture architectural mode. When bit 135
> 	     is one, bit 129 is also one.
>
> Looks like we confuse the vector enhancements facility 1 ("EXT") with the
> Vector packed decimal facility ("BCD"). Let's fix the facility checks.
>
> Detected while working on QEMU/tcg z14 support and only unlocking
> the vector enhancements facility 1, but not the vector packed decimal
> facility.
>
> Fixes: 2583b848cad0 ("s390: report new vector facilities")
> Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> Cc: Sven Schnelle <svens@xxxxxxxxxxxxx>
> Cc: Alexander Egorenkov <egorenar@xxxxxxxxxxxxx>
> Cc: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
> Cc: Janosch Frank <frankja@xxxxxxxxxxxxx>
> Cc: linux-s390@xxxxxxxxxxxxxxx
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>

Yes looks correct. This should not be noticable on real machines as you either
have both or none, but of course with virtual machine this could happen.

Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>

> ---
>   arch/s390/kernel/setup.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
> index 72134f9f6ff5..5aab59ad5688 100644
> --- a/arch/s390/kernel/setup.c
> +++ b/arch/s390/kernel/setup.c
> @@ -937,9 +937,9 @@ static int __init setup_hwcaps(void)
>   	if (MACHINE_HAS_VX) {
>   		elf_hwcap |= HWCAP_S390_VXRS;
>   		if (test_facility(134))
> -			elf_hwcap |= HWCAP_S390_VXRS_EXT;
> -		if (test_facility(135))
>   			elf_hwcap |= HWCAP_S390_VXRS_BCD;
> +		if (test_facility(135))
> +			elf_hwcap |= HWCAP_S390_VXRS_EXT;
>   		if (test_facility(148))
>   			elf_hwcap |= HWCAP_S390_VXRS_EXT2;
>   		if (test_facility(152))