Re: [PATCH v1 2/2] s390/kvm: VSIE: fix MVPG handling for prefixing and MSO

David Hildenbrand
2021-03-22T09:56:41Z

On 19.03.21 20:33, Claudio Imbrenda wrote:
> Prefixing needs to be applied to the guest real address to translate it
> into a guest absolute address.
>
> The value of MSO needs to be added to a guest-absolute address in order to
> obtain the host-virtual.
>
> Fixes: 223ea46de9e79 ("s390/kvm: VSIE: correctly handle MVPG when in VSIE")
> Cc: stable@vger.kernel.org
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
> arch/s390/kvm/vsie.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
> index 48aab6290a77..92864f9b3d84 100644
> --- a/arch/s390/kvm/vsie.c
> +++ b/arch/s390/kvm/vsie.c
> @@ -1002,7 +1002,7 @@ static u64 vsie_get_register(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page,
> static int vsie_handle_mvpg(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> {
> struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
> - unsigned long pei_dest, pei_src, src, dest, mask;
> + unsigned long pei_dest, pei_src, r1, r2, src, dest, mask, mso, prefix;
> u64 *pei_block = &vsie_page->scb_o->mcic;
> int edat, rc_dest, rc_src;
> union ctlreg0 cr0;
> @@ -1010,9 +1010,13 @@ static int vsie_handle_mvpg(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> cr0.val = vcpu->arch.sie_block->gcr[0];
> edat = cr0.edat && test_kvm_facility(vcpu->kvm, 8);
> mask = _kvm_s390_logical_to_effective(&scb_s->gpsw, PAGE_MASK);
> + mso = READ_ONCE(vsie_page->scb_o->mso) & ~(1UL << 20);

I think we should use the one stored in the shadow page - this is what
the SIE saw and will see when retrying.

> + prefix = scb_s->prefix << GUEST_PREFIX_SHIFT;
>
> - dest = vsie_get_register(vcpu, vsie_page, scb_s->ipb >> 16) & mask;
> - src = vsie_get_register(vcpu, vsie_page, scb_s->ipb >> 20) & mask;
> + r1 = vsie_get_register(vcpu, vsie_page, scb_s->ipb >> 16);
> + r2 = vsie_get_register(vcpu, vsie_page, scb_s->ipb >> 20);

Just reuse dest and src here?

> + dest = _kvm_s390_real_to_abs(prefix, r1 & mask) + mso;
> + src = _kvm_s390_real_to_abs(prefix, r2 & mask) + mso;
>
> rc_dest = kvm_s390_shadow_fault(vcpu, vsie_page->gmap, dest, &pei_dest);
> rc_src = kvm_s390_shadow_fault(vcpu, vsie_page->gmap, src, &pei_src);
>

Apart from that, looks good to me.

--
Thanks,

David / dhildenb