Re: [PATCH 4/4] KVM: s390: Fix skey emulation permission check

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On 05.12.2017 09:33, Christian Borntraeger wrote:
> From: Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>
> 
> All skey functions call skey_check_enable at their start, which checks
> if we are in the PSTATE and injects a privileged operation exception
> if we are.

Correct thing to do, are we sure we even get an intercept?
(no documentation at hand :( )

> 
> Unfortunately they continue processing afterwards and perform the
> operation anyhow as skey_check_enable does not deliver an error if the
> exception injection was successful.
> 
> Let's move the PSTATE check into the skey functions and exit them on
> such an occasion, also we now do not enable skey handling anymore in
> such a case.
> 
> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>
> Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> Fixes: a7e19ab ("KVM: s390: handle missing storage-key facility")
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.8+
> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> ---
>  arch/s390/kvm/priv.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index 28b69ab..572496c 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -232,8 +232,6 @@ static int try_handle_skey(struct kvm_vcpu *vcpu)
>  		VCPU_EVENT(vcpu, 4, "%s", "retrying storage key operation");
>  		return -EAGAIN;
>  	}
> -	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
> -		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
>  	return 0;
>  }
>  
> @@ -244,6 +242,9 @@ static int handle_iske(struct kvm_vcpu *vcpu)
>  	int reg1, reg2;
>  	int rc;
>  
> +	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
> +		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
> +
>  	rc = try_handle_skey(vcpu);
>  	if (rc)
>  		return rc != -EAGAIN ? rc : 0;
> @@ -273,6 +274,9 @@ static int handle_rrbe(struct kvm_vcpu *vcpu)
>  	int reg1, reg2;
>  	int rc;
>  
> +	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
> +		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
> +
>  	rc = try_handle_skey(vcpu);
>  	if (rc)
>  		return rc != -EAGAIN ? rc : 0;
> @@ -308,6 +312,9 @@ static int handle_sske(struct kvm_vcpu *vcpu)
>  	int reg1, reg2;
>  	int rc;
>  
> +	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
> +		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
> +
>  	rc = try_handle_skey(vcpu);
>  	if (rc)
>  		return rc != -EAGAIN ? rc : 0;
> 


-- 

Thanks,

David / dhildenb
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