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

Janis Schoetterl-Glausch
2021-11-29T09:19:50Z

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

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;
>