Re: [PATCH v2 24/42] KVM: s390: protvirt: STSI handling

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On 14.02.20 23:26, Christian Borntraeger wrote:
> From: Janosch Frank <frankja@xxxxxxxxxxxxx>
> 
> Save response to sidad and disable address checking for protected
> guests.
> 
> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
> Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
> Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>
> [borntraeger@xxxxxxxxxx: patch merging, splitting, fixing]
> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> ---
>  arch/s390/kvm/priv.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index ed52ffa8d5d4..b2de7dc5f58d 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -872,7 +872,7 @@ static int handle_stsi(struct kvm_vcpu *vcpu)
>  
>  	operand2 = kvm_s390_get_base_disp_s(vcpu, &ar);
>  
> -	if (operand2 & 0xfff)
> +	if (!kvm_s390_pv_is_protected(vcpu->kvm) && (operand2 & 0xfff))
>  		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);

Why is that needed? I'd assume the hardware handles this for us and this
case can never happen for PV? (IOW, change is not necessary)

>  
>  	switch (fc) {
> @@ -893,8 +893,13 @@ static int handle_stsi(struct kvm_vcpu *vcpu)
>  		handle_stsi_3_2_2(vcpu, (void *) mem);
>  		break;
>  	}
> -
> -	rc = write_guest(vcpu, operand2, ar, (void *)mem, PAGE_SIZE);
> +	if (kvm_s390_pv_is_protected(vcpu->kvm)) {
> +		memcpy((void *)sida_origin(vcpu->arch.sie_block), (void *)mem,
> +		       PAGE_SIZE);
> +		rc = 0;
> +	} else {
> +		rc = write_guest(vcpu, operand2, ar, (void *)mem, PAGE_SIZE);
> +	}
>  	if (rc) {
>  		rc = kvm_s390_inject_prog_cond(vcpu, rc);
>  		goto out;
> 

I'd pull the interrupt injection into the else case, makes things clearer.

What about user_stsi? Will that still work? (I assume user space will
write to the sida and it should work just fine)

(I assume races regarding kvm_s390_pv_is_protected() will be dealt with
in your next series)

In general, looks good to me.

-- 
Thanks,

David / dhildenb





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