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-rw-r--r--arch/powerpc/kvm/book3s_xive.h11
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/powerpc/kvm/book3s_xive.h b/arch/powerpc/kvm/book3s_xive.h
index d5d4fee7ac94..86c24a4ad809 100644
--- 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);