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Subject: Re: [PATCH v1 5/5] KVM: s390: vsie: gmap_table_walk() simplifications
To:     David Hildenbrand <david@redhat.com>, kvm@vger.kernel.org
Cc:     linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        Vasily Gorbik <gor@linux.ibm.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Cornelia Huck <cohuck@redhat.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>
References: <20200402184819.34215-1-david@redhat.com>
 <20200402184819.34215-6-david@redhat.com>
From:   Janosch Frank <frankja@linux.ibm.com>
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Date:   Fri, 3 Apr 2020 15:03:04 +0200
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On 4/2/20 8:48 PM, David Hildenbrand wrote:
> Let's use asce_type where applicable. Also, simplify our sanity check f=
or
> valid table levels and convert it into a WARN_ON_ONCE(). Check if we ev=
en
> have a valid gmap shadow as the very first step.
>=20
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  arch/s390/mm/gmap.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>=20
> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> index fd32ab566f57..3c801dae7988 100644
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -790,17 +790,18 @@ static inline unsigned long *gmap_table_walk(stru=
ct gmap *gmap,
>  	const int asce_type =3D gmap->asce & _ASCE_TYPE_MASK;
>  	unsigned long *table;
> =20
> -	if ((gmap->asce & _ASCE_TYPE_MASK) + 4 < (level * 4))
> -		return NULL;
>  	if (gmap_is_shadow(gmap) && gmap->removed)
>  		return NULL;
> =20
> +	if (WARN_ON_ONCE(level > (asce_type >> 2) + 1))
> +		return NULL;
> +
>  	if (WARN_ON_ONCE(asce_type !=3D _ASCE_TYPE_REGION1) &&
>  			 gaddr & (-1UL << (31 + (asce_type >> 2) * 11)))
>  		return NULL;
> =20
>  	table =3D gmap->table;

We could also initialize this variable at the top, no?

> -	switch (gmap->asce & _ASCE_TYPE_MASK) {
> +	switch (asce_type) {
>  	case _ASCE_TYPE_REGION1:
>  		table +=3D (gaddr & _REGION1_INDEX) >> _REGION1_SHIFT;
>  		if (level =3D=3D 4)
>=20


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