KVM: PPC: Book3S HV: XIVE: Add a comment regarding VP numbering

[sfrench/cifs-2.6.git] / arch / powerpc / kvm / book3s_xive.h

diff --git a/arch/powerpc/kvm/book3s_xive.h b/arch/powerpc/kvm/book3s_xive.h
index 382e3a56e78964badab571cf32f998cfb9750cf9..86c24a4ad8093e816e50702da557bd9695da1f2a 100644 (file)
--- a/arch/powerpc/kvm/book3s_xive.h
+++ b/arch/powerpc/kvm/book3s_xive.h
@@ -218,6 +218,17 @@ static inline struct kvmppc_xive_src_block *kvmppc_xive_find_source(struct kvmpp
        return xive->src_blocks[bid];
 }
 
+/*
+ * When the XIVE resources are allocated at the HW level, the VP
+ * structures describing the vCPUs of a guest are distributed among
+ * the chips to optimize the PowerBUS usage. For best performance, the
+ * guest vCPUs can be pinned to match the VP structure distribution.
+ *
+ * Currently, the VP identifiers are deduced from the vCPU id using
+ * the kvmppc_pack_vcpu_id() routine which is not incorrect but not
+ * optimal either. It VSMT is used, the result is not continuous and
+ * the constraints on HW resources described above can not be met.
+ */
 static inline u32 kvmppc_xive_vp(struct kvmppc_xive *xive, u32 server)
 {
        return xive->vp_base + kvmppc_pack_vcpu_id(xive->kvm, server);
@@ -290,6 +301,8 @@ extern int (*__xive_vm_h_eoi)(struct kvm_vcpu *vcpu, unsigned long xirr);
  */
 void kvmppc_xive_disable_vcpu_interrupts(struct kvm_vcpu *vcpu);
 int kvmppc_xive_debug_show_queues(struct seq_file *m, struct kvm_vcpu *vcpu);
+void kvmppc_xive_debug_show_sources(struct seq_file *m,
+                                   struct kvmppc_xive_src_block *sb);
 struct kvmppc_xive_src_block *kvmppc_xive_create_src_block(
        struct kvmppc_xive *xive, int irq);
 void kvmppc_xive_free_sources(struct kvmppc_xive_src_block *sb);