KVM: s390: Change virtual to physical address access in diag 0x258 handler

The parameters for the diag 0x258 are real addresses, not virtual, but
KVM was using them as virtual addresses. This only happened to work, since
the Linux kernel as a guest used to have a 1:1 mapping for physical vs
virtual addresses.

Fix KVM so that it correctly uses the addresses as real addresses.

Cc: [email protected]
Fixes: 8ae04b8 ("KVM: s390: Guest's memory access functions get access registers")
Suggested-by: Vasily Gorbik <[email protected]>
Signed-off-by: Michael Mueller <[email protected]>
Signed-off-by: Nico Boehr <[email protected]>
Reviewed-by: Christian Borntraeger <[email protected]>
Reviewed-by: Heiko Carstens <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Acked-by: Janosch Frank <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>

Author: Michael Mueller

arch/s390/kvm/diag.c

@@ -77,7 +77,7 @@ static int __diag_page_ref_service(struct kvm_vcpu *vcpu)
 	vcpu->stat.instruction_diagnose_258++;
 	if (vcpu->run->s.regs.gprs[rx] & 7)
 		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
-	rc = read_guest(vcpu, vcpu->run->s.regs.gprs[rx], rx, &parm, sizeof(parm));
+	rc = read_guest_real(vcpu, vcpu->run->s.regs.gprs[rx], &parm, sizeof(parm));
 	if (rc)
 		return kvm_s390_inject_prog_cond(vcpu, rc);
 	if (parm.parm_version != 2 || parm.parm_len < 5 || parm.code != 0x258)