KVM: powerpc: Map guest userspace with TID=0 mappings
When we use TID=N userspace mappings, we must ensure that kernel mappings have
been destroyed when entering userspace. Using TID=1/TID=0 for kernel/user
mappings and running userspace with PID=0 means that userspace can't access the
kernel mappings, but the kernel can directly access userspace.
The net is that we don't need to flush the TLB on privilege switches, but we do
on guest context switches (which are far more infrequent). Guest boot time
performance improvement: about 30%.
Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/arch/powerpc/kvm/booke_interrupts.S b/arch/powerpc/kvm/booke_interrupts.S
index 564ea32..95e165b 100644
--- a/arch/powerpc/kvm/booke_interrupts.S
+++ b/arch/powerpc/kvm/booke_interrupts.S
@@ -332,7 +332,7 @@
mfspr r3, SPRN_PID
stw r3, VCPU_HOST_PID(r4)
- lwz r3, VCPU_PID(r4)
+ lwz r3, VCPU_SHADOW_PID(r4)
mtspr SPRN_PID, r3
/* Prevent all asynchronous TLB updates. */