KVM: PPC: e500mc: Add support for single threaded vcpus on e6500 core

ePAPR represents hardware threads as cpu node properties in device tree.
So with existing QEMU, hardware threads are simply exposed as vcpus with
one hardware thread.

The e6500 core shares TLBs between hardware threads. Without tlb write
conditional instruction, the Linux kernel uses per core mechanisms to
protect against duplicate TLB entries.

The guest is unable to detect real siblings threads, so it can't use the
TLB protection mechanism. An alternative solution is to use the hypervisor
to allocate different lpids to guest's vcpus that runs simultaneous on real
siblings threads. On systems with two threads per core this patch halves
the size of the lpid pool that the allocator sees and use two lpids per VM.
Use even numbers to speedup vcpu lpid computation with consecutive lpids
per VM: vm1 will use lpids 2 and 3, vm2 lpids 4 and 5, and so on.

Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com>
[agraf: fix spelling]
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 20 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/e500.h b/arch/powerpc/kvm/e500.h
index a326178bdea5..72920bed3ac6 100644
--- a/arch/powerpc/kvm/e500.h
+++ b/arch/powerpc/kvm/e500.h
@@ -22,6 +22,7 @@
 #include <linux/kvm_host.h>
 #include <asm/mmu-book3e.h>
 #include <asm/tlb.h>
+#include <asm/cputhreads.h>
 
 enum vcpu_ftr {
 	VCPU_FTR_MMU_V2
@@ -289,6 +290,25 @@ void kvmppc_e500_tlbil_all(struct kvmppc_vcpu_e500 *vcpu_e500);
 #define kvmppc_e500_get_tlb_stid(vcpu, gtlbe)       get_tlb_tid(gtlbe)
 #define get_tlbmiss_tid(vcpu)           get_cur_pid(vcpu)
 #define get_tlb_sts(gtlbe)              (gtlbe->mas1 & MAS1_TS)
+
+/*
+ * These functions should be called with preemption disabled
+ * and the returned value is valid only in that context
+ */
+static inline int get_thread_specific_lpid(int vm_lpid)
+{
+	int vcpu_lpid = vm_lpid;
+
+	if (threads_per_core == 2)
+		vcpu_lpid |= smp_processor_id() & 1;
+
+	return vcpu_lpid;
+}
+
+static inline int get_lpid(struct kvm_vcpu *vcpu)
+{
+	return get_thread_specific_lpid(vcpu->kvm->arch.lpid);
+}
 #else
 unsigned int kvmppc_e500_get_tlb_stid(struct kvm_vcpu *vcpu,
 				      struct kvm_book3e_206_tlb_entry *gtlbe);