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

Claudio Imbrenda
2021-11-29T09:15:40Z

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>

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 ?

(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;