KVM: ppc: Write only modified shadow entries into the TLB on exit

Track which TLB entries need to be written, instead of overwriting everything
below the high water mark. Typically only a single guest TLB entry will be
modified in a single exit.

Guest boot time performance improvement: about 15%.

Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index b75607180ddb..90a6fc422b23 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -27,6 +27,7 @@
 #include <asm/cputable.h>
 #include <asm/uaccess.h>
 #include <asm/kvm_ppc.h>
+#include <asm/tlbflush.h>
 
 
 gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
@@ -307,14 +308,28 @@ static void kvmppc_load_guest_debug_registers(struct kvm_vcpu *vcpu)
 
 void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
+        int i;
+
         if (vcpu->guest_debug.enabled)
                 kvmppc_load_guest_debug_registers(vcpu);
+
+        /* Mark every guest entry in the shadow TLB entry modified, so that they
+         * will all be reloaded on the next vcpu run (instead of being
+         * demand-faulted). */
+        for (i = 0; i <= tlb_44x_hwater; i++)
+                kvmppc_tlbe_set_modified(vcpu, i);
 }
 
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 {
         if (vcpu->guest_debug.enabled)
                 kvmppc_restore_host_debug_state(vcpu);
+
+        /* Don't leave guest TLB entries resident when being de-scheduled. */
+        /* XXX It would be nice to differentiate between heavyweight exit and
+         * sched_out here, since we could avoid the TLB flush for heavyweight
+         * exits. */
+        _tlbia();
 }
 
 int kvm_arch_vcpu_ioctl_debug_guest(struct kvm_vcpu *vcpu,