KVM: PPC: Book3S: Introduce hypervisor call H_GET_TCE

This introduces the H_GET_TCE hypervisor call, which is basically the
reverse of H_PUT_TCE, as defined in the Power Architecture Platform
Requirements (PAPR).

The hcall H_GET_TCE is required by the kdump kernel, which uses it to
retrieve TCEs set up by the previous (panicked) kernel.
Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/include/asm/kvm_ppc.h

@@ -129,6 +129,8 @@ extern long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
 				struct kvm_create_spapr_tce *args);
 extern long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
 			     unsigned long ioba, unsigned long tce);
+extern long kvmppc_h_get_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
+			     unsigned long ioba);
 extern struct kvm_rma_info *kvm_alloc_rma(void);
 extern void kvm_release_rma(struct kvm_rma_info *ri);
 extern struct page *kvm_alloc_hpt(unsigned long nr_pages);

arch/powerpc/kvm/book3s_64_vio_hv.c

@@ -75,3 +75,31 @@ long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
 	return H_TOO_HARD;
 }
 EXPORT_SYMBOL_GPL(kvmppc_h_put_tce);
+
+long kvmppc_h_get_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
+		      unsigned long ioba)
+{
+	struct kvm *kvm = vcpu->kvm;
+	struct kvmppc_spapr_tce_table *stt;
+
+	list_for_each_entry(stt, &kvm->arch.spapr_tce_tables, list) {
+		if (stt->liobn == liobn) {
+			unsigned long idx = ioba >> SPAPR_TCE_SHIFT;
+			struct page *page;
+			u64 *tbl;
+
+			if (ioba >= stt->window_size)
+				return H_PARAMETER;
+
+			page = stt->pages[idx / TCES_PER_PAGE];
+			tbl = (u64 *)page_address(page);
+
+			vcpu->arch.gpr[4] = tbl[idx % TCES_PER_PAGE];
+			return H_SUCCESS;
+		}
+	}
+
+	/* Didn't find the liobn, punt it to userspace */
+	return H_TOO_HARD;
+}
+EXPORT_SYMBOL_GPL(kvmppc_h_get_tce);

arch/powerpc/kvm/book3s_hv_rmhandlers.S

@@ -1691,7 +1691,7 @@ hcall_real_table:
 	.long	0		/* 0x10 - H_CLEAR_MOD */
 	.long	0		/* 0x14 - H_CLEAR_REF */
 	.long	.kvmppc_h_protect - hcall_real_table
-	.long	0		/* 0x1c - H_GET_TCE */
+	.long	.kvmppc_h_get_tce - hcall_real_table
 	.long	.kvmppc_h_put_tce - hcall_real_table
 	.long	0		/* 0x24 - H_SET_SPRG0 */
 	.long	.kvmppc_h_set_dabr - hcall_real_table