Re: [PATCH v2 23/42] KVM: s390: protvirt: Write sthyi data to instruction data area

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On 14.02.20 23:26, Christian Borntraeger wrote:
> From: Janosch Frank <frankja@xxxxxxxxxxxxx>
> 
> STHYI data has to go through the bounce buffer.
> 
> 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/intercept.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
> index 1e231058e4b3..cfabeecbb777 100644
> --- a/arch/s390/kvm/intercept.c
> +++ b/arch/s390/kvm/intercept.c
> @@ -392,7 +392,7 @@ int handle_sthyi(struct kvm_vcpu *vcpu)
>  		goto out;
>  	}
>  
> -	if (addr & ~PAGE_MASK)
> +	if (!kvm_s390_pv_is_protected(vcpu->kvm) && (addr & ~PAGE_MASK))
>  		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
>  
>  	sctns = (void *)get_zeroed_page(GFP_KERNEL);
> @@ -403,10 +403,15 @@ int handle_sthyi(struct kvm_vcpu *vcpu)
>  
>  out:
>  	if (!cc) {
> -		r = write_guest(vcpu, addr, reg2, sctns, PAGE_SIZE);
> -		if (r) {
> -			free_page((unsigned long)sctns);
> -			return kvm_s390_inject_prog_cond(vcpu, r);
> +		if (kvm_s390_pv_is_protected(vcpu->kvm)) {

I have the feeling that we might have to think about proper locking for
kvm_s390_pv_is_protected(). We have to make sure there cannot be any
races with user space. Smells like a new r/w lock maybe.


-- 
Thanks,

David / dhildenb




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