Re: [PATCH v3 3/3] KVM: s390: gaccess: Cleanup access to guest pages

[Janis Schoetterl-Glausch]

On 11/29/21 09:59, Claudio Imbrenda wrote:
> On Fri, 26 Nov 2021 17:45:49 +0100
> Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx> wrote:
> 
>> Introduce a helper function for guest frame access.
>>
>> Signed-off-by: Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx>
>> Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
> 
> Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>

Thanks.
> 
> see a small nit below
> 
>> ---
>>  arch/s390/kvm/gaccess.c | 24 ++++++++++++++++--------
>>  1 file changed, 16 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
>> index c09659609d68..9193f0de40b1 100644
>> --- a/arch/s390/kvm/gaccess.c
>> +++ b/arch/s390/kvm/gaccess.c
>> @@ -866,6 +866,20 @@ static int guest_range_to_gpas(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
>>  	return 0;
>>  }
>>  
>> +static int access_guest_page(struct kvm *kvm, enum gacc_mode mode, gpa_t gpa,
>> +			     void *data, unsigned int len)
>> +{
>> +	const unsigned int offset = offset_in_page(gpa);
>> +	const gfn_t gfn = gpa_to_gfn(gpa);
>> +	int rc;
>> +
>> +	if (mode == GACC_STORE)
>> +		rc = kvm_write_guest_page(kvm, gfn, data, offset, len);
> 
> why not just return ?

No clue, maybe I wanted to look at the rc while debugging something?
> 
> (but don't bother with a v4, it's ok anyway)
> 
>> +	else
>> +		rc = kvm_read_guest_page(kvm, gfn, data, offset, len);
>> +	return rc;
>> +}
>> +
>>  int access_guest(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data,
>>  		 unsigned long len, enum gacc_mode mode)
>>  {
>> @@ -896,10 +910,7 @@ int access_guest(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data,
>>  	rc = guest_range_to_gpas(vcpu, ga, ar, gpas, len, asce, mode);
>>  	for (idx = 0; idx < nr_pages && !rc; idx++) {
>>  		fragment_len = min(PAGE_SIZE - offset_in_page(gpas[idx]), len);
>> -		if (mode == GACC_STORE)
>> -			rc = kvm_write_guest(vcpu->kvm, gpas[idx], data, fragment_len);
>> -		else
>> -			rc = kvm_read_guest(vcpu->kvm, gpas[idx], data, fragment_len);
>> +		rc = access_guest_page(vcpu->kvm, mode, gpas[idx], data, fragment_len);
>>  		len -= fragment_len;
>>  		data += fragment_len;
>>  	}
>> @@ -920,10 +931,7 @@ int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra,
>>  	while (len && !rc) {
>>  		gpa = kvm_s390_real_to_abs(vcpu, gra);
>>  		fragment_len = min(PAGE_SIZE - offset_in_page(gpa), len);
>> -		if (mode)
>> -			rc = write_guest_abs(vcpu, gpa, data, fragment_len);
>> -		else
>> -			rc = read_guest_abs(vcpu, gpa, data, fragment_len);
>> +		rc = access_guest_page(vcpu->kvm, mode, gpa, data, fragment_len);
>>  		len -= fragment_len;
>>  		gra += fragment_len;
>>  		data += fragment_len;
>