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, 8 insertions, 1 deletions

diff --git a/arch/powerpc/kvm/44x_tlb.c b/arch/powerpc/kvm/44x_tlb.c
index a207d16b9dbb..06a5fcfc4d33 100644
--- a/arch/powerpc/kvm/44x_tlb.c
+++ b/arch/powerpc/kvm/44x_tlb.c
@@ -125,6 +125,11 @@ static void kvmppc_44x_shadow_release(struct kvm_vcpu *vcpu,
         }
 }
 
+void kvmppc_tlbe_set_modified(struct kvm_vcpu *vcpu, unsigned int i)
+{
+    vcpu->arch.shadow_tlb_mod[i] = 1;
+}
+
 /* Caller must ensure that the specified guest TLB entry is safe to insert into
  * the shadow TLB. */
 void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gfn_t gfn, u64 asid,
@@ -172,10 +177,10 @@ void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 gvaddr, gfn_t gfn, u64 asid,
          * use host large pages in the future. */
         stlbe->word0 = (gvaddr & PAGE_MASK) | PPC44x_TLB_VALID | PPC44x_TLB_TS
                        | PPC44x_TLB_4K;
-
         stlbe->word1 = (hpaddr & 0xfffffc00) | ((hpaddr >> 32) & 0xf);
         stlbe->word2 = kvmppc_44x_tlb_shadow_attrib(flags,
                                                     vcpu->arch.msr & MSR_PR);
+        kvmppc_tlbe_set_modified(vcpu, victim);
 
         KVMTRACE_5D(STLB_WRITE, vcpu, victim,
                         stlbe->tid, stlbe->word0, stlbe->word1, stlbe->word2,
@@ -209,6 +214,7 @@ void kvmppc_mmu_invalidate(struct kvm_vcpu *vcpu, gva_t eaddr,
 
                 kvmppc_44x_shadow_release(vcpu, i);
                 stlbe->word0 = 0;
+                kvmppc_tlbe_set_modified(vcpu, i);
                 KVMTRACE_5D(STLB_INVAL, vcpu, i,
                                 stlbe->tid, stlbe->word0, stlbe->word1,
                                 stlbe->word2, handler);
@@ -229,6 +235,7 @@ void kvmppc_mmu_priv_switch(struct kvm_vcpu *vcpu, int usermode)
 
                 kvmppc_44x_shadow_release(vcpu, i);
                 stlbe->word0 = 0;
+                kvmppc_tlbe_set_modified(vcpu, i);
                 KVMTRACE_5D(STLB_INVAL, vcpu, i,
                                 stlbe->tid, stlbe->word0, stlbe->word1,
                                 stlbe->word2, handler);