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>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 4338b03da8f..34b52b7180c 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -129,7 +129,11 @@ struct kvm_vcpu_arch {
 	u32 ivor[16];
 	u32 ivpr;
 	u32 pir;
+
+	u32 shadow_pid;
 	u32 pid;
+	u32 swap_pid;
+
 	u32 pvr;
 	u32 ccr0;
 	u32 ccr1;