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>

3 files changed, 57 insertions, 18 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);
diff --git a/arch/powerpc/kvm/booke_interrupts.S b/arch/powerpc/kvm/booke_interrupts.S
index 3e88dfa1dbe4..564ea32ecbac 100644
--- a/arch/powerpc/kvm/booke_interrupts.S
+++ b/arch/powerpc/kvm/booke_interrupts.S
@@ -335,7 +335,7 @@ lightweight_exit:
         lwz     r3, VCPU_PID(r4)
         mtspr   SPRN_PID, r3
 
-        /* Prevent all TLB updates. */
+        /* Prevent all asynchronous TLB updates. */
         mfmsr   r5
         lis     r6, (MSR_EE|MSR_CE|MSR_ME|MSR_DE)@h
         ori     r6, r6, (MSR_EE|MSR_CE|MSR_ME|MSR_DE)@l
@@ -344,28 +344,45 @@ lightweight_exit:
 
         /* Load the guest mappings, leaving the host's "pinned" kernel mappings
          * in place. */
-        /* XXX optimization: load only modified guest entries. */
         mfspr   r10, SPRN_MMUCR                 /* Save host MMUCR. */
-        lis     r8, tlb_44x_hwater@ha
-        lwz     r8, tlb_44x_hwater@l(r8)
-        addi    r9, r4, VCPU_SHADOW_TLB - 4
-        li      r6, 0
+        li      r5, PPC44x_TLB_SIZE
+        lis     r5, tlb_44x_hwater@ha
+        lwz     r5, tlb_44x_hwater@l(r5)
+        mtctr   r5
+        addi    r9, r4, VCPU_SHADOW_TLB
+        addi    r5, r4, VCPU_SHADOW_MOD
+        li      r3, 0
 1:
+        lbzx    r7, r3, r5
+        cmpwi   r7, 0
+        beq     3f
+
         /* Load guest entry. */
-        lwzu    r7, 4(r9)
+        mulli   r11, r3, TLBE_BYTES
+        add     r11, r11, r9
+        lwz     r7, 0(r11)
         mtspr   SPRN_MMUCR, r7
-        lwzu    r7, 4(r9)
-        tlbwe   r7, r6, PPC44x_TLB_PAGEID
-        lwzu    r7, 4(r9)
-        tlbwe   r7, r6, PPC44x_TLB_XLAT
-        lwzu    r7, 4(r9)
-        tlbwe   r7, r6, PPC44x_TLB_ATTRIB
-        /* Increment index. */
-        addi    r6, r6, 1
-        cmpw    r6, r8
-        blt     1b
+        lwz     r7, 4(r11)
+        tlbwe   r7, r3, PPC44x_TLB_PAGEID
+        lwz     r7, 8(r11)
+        tlbwe   r7, r3, PPC44x_TLB_XLAT
+        lwz     r7, 12(r11)
+        tlbwe   r7, r3, PPC44x_TLB_ATTRIB
+3:
+        addi    r3, r3, 1                       /* Increment index. */
+        bdnz    1b
+
         mtspr   SPRN_MMUCR, r10                 /* Restore host MMUCR. */
 
+        /* Clear bitmap of modified TLB entries */
+        li      r5, PPC44x_TLB_SIZE>>2
+        mtctr   r5
+        addi    r5, r4, VCPU_SHADOW_MOD - 4
+        li      r6, 0
+1:
+        stwu    r6, 4(r5)
+        bdnz    1b
+
         iccci   0, 0 /* XXX hack */
 
         /* Load some guest volatiles. */
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,