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SubjectRe: [PATCH v2 2/2] s390/kvm: VSIE: fix MVPG handling for prefixing and MSO
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On 22.03.21 15:05, 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>
> Reported-by: Janosch Frank <frankja@linux.ibm.com>
> ---
> arch/s390/kvm/vsie.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
> index 48aab6290a77..ac86f11e46dc 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, dest, src, 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 = scb_s->mso & ~(1UL << 20);
> + prefix = scb_s->prefix << GUEST_PREFIX_SHIFT;
>
> dest = vsie_get_register(vcpu, vsie_page, scb_s->ipb >> 16) & mask;
> + dest = _kvm_s390_real_to_abs(prefix, dest) + mso;
> src = vsie_get_register(vcpu, vsie_page, scb_s->ipb >> 20) & mask;
> + src = _kvm_s390_real_to_abs(prefix, src) + 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);
>

mso is always confusing, but I think this should be correct.

Reviewed-by: David Hildenbrand <david@redhat.com>

--
Thanks,

David / dhildenb

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