Re: [PATCH v2 1/2] KVM: s390: Don't indicate suppression on dirtying, failing memop

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

On Mon, 25 Apr 2022 12:01:46 +0200
Janis Schoetterl-Glausch <scgl@linux.ibm.com> wrote:

> If user space uses a memop to emulate an instruction and that
> memop fails, the execution of the instruction ends.
> Instruction execution can end in different ways, one of which is
> suppression, which requires that the instruction execute like a no-op.
> A writing memop that spans multiple pages and fails due to key
> protection can modified guest memory, as a result, the likely
> correct ending is termination. Therefore do not indicate a
> suppressing instruction ending in this case.
> 
> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>

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

> ---
>  arch/s390/kvm/gaccess.c | 47 ++++++++++++++++++++++++-----------------
>  1 file changed, 28 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
> index d53a183c2005..3b1fbef82288 100644
> --- a/arch/s390/kvm/gaccess.c
> +++ b/arch/s390/kvm/gaccess.c
> @@ -491,8 +491,8 @@ enum prot_type {
>  	PROT_TYPE_IEP  = 4,
>  };
>  
> -static int trans_exc(struct kvm_vcpu *vcpu, int code, unsigned long gva,
> -		     u8 ar, enum gacc_mode mode, enum prot_type prot)
> +static int trans_exc_ending(struct kvm_vcpu *vcpu, int code, unsigned long gva, u8 ar,
> +			    enum gacc_mode mode, enum prot_type prot, bool suppress)
>  {
>  	struct kvm_s390_pgm_info *pgm = &vcpu->arch.pgm;
>  	struct trans_exc_code_bits *tec;
> @@ -503,22 +503,24 @@ static int trans_exc(struct kvm_vcpu *vcpu, int code, unsigned long gva,
>  
>  	switch (code) {
>  	case PGM_PROTECTION:
> -		switch (prot) {
> -		case PROT_TYPE_IEP:
> -			tec->b61 = 1;
> -			fallthrough;
> -		case PROT_TYPE_LA:
> -			tec->b56 = 1;
> -			break;
> -		case PROT_TYPE_KEYC:
> -			tec->b60 = 1;
> -			break;
> -		case PROT_TYPE_ALC:
> -			tec->b60 = 1;
> -			fallthrough;
> -		case PROT_TYPE_DAT:
> -			tec->b61 = 1;
> -			break;
> +		if (suppress) {
> +			switch (prot) {
> +			case PROT_TYPE_IEP:
> +				tec->b61 = 1;
> +				fallthrough;
> +			case PROT_TYPE_LA:
> +				tec->b56 = 1;
> +				break;
> +			case PROT_TYPE_KEYC:
> +				tec->b60 = 1;
> +				break;
> +			case PROT_TYPE_ALC:
> +				tec->b60 = 1;
> +				fallthrough;
> +			case PROT_TYPE_DAT:
> +				tec->b61 = 1;
> +				break;
> +			}
>  		}
>  		fallthrough;
>  	case PGM_ASCE_TYPE:
> @@ -552,6 +554,12 @@ static int trans_exc(struct kvm_vcpu *vcpu, int code, unsigned long gva,
>  	return code;
>  }
>  
> +static int trans_exc(struct kvm_vcpu *vcpu, int code, unsigned long gva, u8 ar,
> +		     enum gacc_mode mode, enum prot_type prot)
> +{
> +	return trans_exc_ending(vcpu, code, gva, ar, mode, prot, true);
> +}
> +
>  static int get_vcpu_asce(struct kvm_vcpu *vcpu, union asce *asce,
>  			 unsigned long ga, u8 ar, enum gacc_mode mode)
>  {
> @@ -1110,7 +1118,8 @@ int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
>  		ga = kvm_s390_logical_to_effective(vcpu, ga + fragment_len);
>  	}
>  	if (rc > 0)
> -		rc = trans_exc(vcpu, rc, ga, ar, mode, prot);
> +		rc = trans_exc_ending(vcpu, rc, ga, ar, mode, prot,
> +				      (mode != GACC_STORE) || (idx == 0));
>  out_unlock:
>  	if (need_ipte_lock)
>  		ipte_unlock(vcpu);