Re: [PATCH v3 1/1] KVM: s390: vsie: clarifications on setting the APCB

Janosch Frank
2023-02-16T13:41:34Z

On 2/14/23 13:28, Pierre Morel wrote:
> The APCB is part of the CRYCB.
> The calculation of the APCB origin can be done by adding
> the APCB offset to the CRYCB origin.
>
> Current code makes confusing transformations, converting
> the CRYCB origin to a pointer to calculate the APCB origin.
>
> Let's make things simpler and keep the CRYCB origin to make
> these calculations.
>
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

LGTM:
Acked-by: Janosch Frank <frankja@linux.ibm.com>

> ---
> arch/s390/kvm/vsie.c | 50 +++++++++++++++++++++++++-------------------
> 1 file changed, 29 insertions(+), 21 deletions(-)
>
> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
> index b6a0219e470a..8d6b765abf29 100644
> --- a/arch/s390/kvm/vsie.c
> +++ b/arch/s390/kvm/vsie.c
> @@ -138,11 +138,15 @@ static int prepare_cpuflags(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> }
> /* Copy to APCB FORMAT1 from APCB FORMAT0 */
> static int setup_apcb10(struct kvm_vcpu *vcpu, struct kvm_s390_apcb1 *apcb_s,
> - unsigned long apcb_o, struct kvm_s390_apcb1 *apcb_h)
> + unsigned long crycb_gpa, struct kvm_s390_apcb1 *apcb_h)
> {
> struct kvm_s390_apcb0 tmp;
> + unsigned long apcb_gpa;
>
> - if (read_guest_real(vcpu, apcb_o, &tmp, sizeof(struct kvm_s390_apcb0)))
> + apcb_gpa = crycb_gpa + offsetof(struct kvm_s390_crypto_cb, apcb0);
> +
> + if (read_guest_real(vcpu, apcb_gpa, &tmp,
> + sizeof(struct kvm_s390_apcb0)))
> return -EFAULT;
>
> apcb_s->apm[0] = apcb_h->apm[0] & tmp.apm[0];
> @@ -157,15 +161,19 @@ static int setup_apcb10(struct kvm_vcpu *vcpu, struct kvm_s390_apcb1 *apcb_s,
> * setup_apcb00 - Copy to APCB FORMAT0 from APCB FORMAT0
> * @vcpu: pointer to the virtual CPU
> * @apcb_s: pointer to start of apcb in the shadow crycb
> - * @apcb_o: pointer to start of original apcb in the guest2
> + * @crycb_gpa: guest physical address to start of original guest crycb
> * @apcb_h: pointer to start of apcb in the guest1
> *
> * Returns 0 and -EFAULT on error reading guest apcb
> */
> static int setup_apcb00(struct kvm_vcpu *vcpu, unsigned long *apcb_s,
> - unsigned long apcb_o, unsigned long *apcb_h)
> + unsigned long crycb_gpa, unsigned long *apcb_h)
> {
> - if (read_guest_real(vcpu, apcb_o, apcb_s,
> + unsigned long apcb_gpa;
> +
> + apcb_gpa = crycb_gpa + offsetof(struct kvm_s390_crypto_cb, apcb0);
> +
> + if (read_guest_real(vcpu, apcb_gpa, apcb_s,
> sizeof(struct kvm_s390_apcb0)))
> return -EFAULT;
>
> @@ -178,16 +186,20 @@ static int setup_apcb00(struct kvm_vcpu *vcpu, unsigned long *apcb_s,
> * setup_apcb11 - Copy the FORMAT1 APCB from the guest to the shadow CRYCB
> * @vcpu: pointer to the virtual CPU
> * @apcb_s: pointer to start of apcb in the shadow crycb
> - * @apcb_o: pointer to start of original guest apcb
> + * @crycb_gpa: guest physical address to start of original guest crycb
> * @apcb_h: pointer to start of apcb in the host
> *
> * Returns 0 and -EFAULT on error reading guest apcb
> */
> static int setup_apcb11(struct kvm_vcpu *vcpu, unsigned long *apcb_s,
> - unsigned long apcb_o,
> + unsigned long crycb_gpa,
> unsigned long *apcb_h)
> {
> - if (read_guest_real(vcpu, apcb_o, apcb_s,
> + unsigned long apcb_gpa;
> +
> + apcb_gpa = crycb_gpa + offsetof(struct kvm_s390_crypto_cb, apcb1);
> +
> + if (read_guest_real(vcpu, apcb_gpa, apcb_s,
> sizeof(struct kvm_s390_apcb1)))
> return -EFAULT;
>
> @@ -200,7 +212,7 @@ static int setup_apcb11(struct kvm_vcpu *vcpu, unsigned long *apcb_s,
> * setup_apcb - Create a shadow copy of the apcb.
> * @vcpu: pointer to the virtual CPU
> * @crycb_s: pointer to shadow crycb
> - * @crycb_o: pointer to original guest crycb
> + * @crycb_gpa: guest physical address of original guest crycb
> * @crycb_h: pointer to the host crycb
> * @fmt_o: format of the original guest crycb.
> * @fmt_h: format of the host crycb.
> @@ -211,50 +223,46 @@ static int setup_apcb11(struct kvm_vcpu *vcpu, unsigned long *apcb_s,
> * Return 0 or an error number if the guest and host crycb are incompatible.
> */
> static int setup_apcb(struct kvm_vcpu *vcpu, struct kvm_s390_crypto_cb *crycb_s,
> - const u32 crycb_o,
> + const u32 crycb_gpa,
> struct kvm_s390_crypto_cb *crycb_h,
> int fmt_o, int fmt_h)
> {
> - struct kvm_s390_crypto_cb *crycb;
> -
> - crycb = (struct kvm_s390_crypto_cb *) (unsigned long)crycb_o;
> -
> switch (fmt_o) {
> case CRYCB_FORMAT2:
> - if ((crycb_o & PAGE_MASK) != ((crycb_o + 256) & PAGE_MASK))
> + if ((crycb_gpa & PAGE_MASK) != ((crycb_gpa + 256) & PAGE_MASK))
> return -EACCES;
> if (fmt_h != CRYCB_FORMAT2)
> return -EINVAL;
> return setup_apcb11(vcpu, (unsigned long *)&crycb_s->apcb1,
> - (unsigned long) &crycb->apcb1,
> + crycb_gpa,
> (unsigned long *)&crycb_h->apcb1);
> case CRYCB_FORMAT1:
> switch (fmt_h) {
> case CRYCB_FORMAT2:
> return setup_apcb10(vcpu, &crycb_s->apcb1,
> - (unsigned long) &crycb->apcb0,
> + crycb_gpa,
> &crycb_h->apcb1);
> case CRYCB_FORMAT1:
> return setup_apcb00(vcpu,
> (unsigned long *) &crycb_s->apcb0,
> - (unsigned long) &crycb->apcb0,
> + crycb_gpa,
> (unsigned long *) &crycb_h->apcb0);
> }
> break;
> case CRYCB_FORMAT0:
> - if ((crycb_o & PAGE_MASK) != ((crycb_o + 32) & PAGE_MASK))
> + if ((crycb_gpa & PAGE_MASK) != ((crycb_gpa + 32) & PAGE_MASK))
> return -EACCES;
>
> switch (fmt_h) {
> case CRYCB_FORMAT2:
> return setup_apcb10(vcpu, &crycb_s->apcb1,
> - (unsigned long) &crycb->apcb0,
> + crycb_gpa,
> &crycb_h->apcb1);
> case CRYCB_FORMAT1:
> case CRYCB_FORMAT0:
> return setup_apcb00(vcpu,
> (unsigned long *) &crycb_s->apcb0,
> - (unsigned long) &crycb->apcb0,
> + crycb_gpa,
> (unsigned long *) &crycb_h->apcb0);
> }
> }