4 files changed, 59 insertions, 6 deletions

diff --git a/arch/powerpc/include/asm/kvm_asm.h b/arch/powerpc/include/asm/kvm_asm.h
index af2abe74f544..aadf2dd6f84e 100644
--- a/arch/powerpc/include/asm/kvm_asm.h
+++ b/arch/powerpc/include/asm/kvm_asm.h
@@ -97,4 +97,10 @@
 #define RESUME_HOST             RESUME_FLAG_HOST
 #define RESUME_HOST_NV          (RESUME_FLAG_HOST|RESUME_FLAG_NV)
 
+#define KVM_GUEST_MODE_NONE     0
+#define KVM_GUEST_MODE_GUEST    1
+#define KVM_GUEST_MODE_SKIP     2
+
+#define KVM_INST_FETCH_FAILED   -1
+
 #endif /* __POWERPC_KVM_ASM_H__ */
diff --git a/arch/powerpc/kvm/book3s_64_rmhandlers.S b/arch/powerpc/kvm/book3s_64_rmhandlers.S
index cd9f0b609e48..9ad1c2645d6f 100644
--- a/arch/powerpc/kvm/book3s_64_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_64_rmhandlers.S
@@ -49,7 +49,7 @@ kvmppc_trampoline_\intno:
         mfcr    r12
         stw     r12, PACA_KVM_SCRATCH1(r13)
         lbz     r12, PACA_KVM_IN_GUEST(r13)
-        cmpwi   r12, 0
+        cmpwi   r12, KVM_GUEST_MODE_NONE
         bne     ..kvmppc_handler_hasmagic_\intno
         /* No KVM guest? Then jump back to the Linux handler! */
         lwz     r12, PACA_KVM_SCRATCH1(r13)
@@ -60,6 +60,11 @@ kvmppc_trampoline_\intno:
 
         /* Now we know we're handling a KVM guest */
 ..kvmppc_handler_hasmagic_\intno:
+
+        /* Should we just skip the faulting instruction? */
+        cmpwi   r12, KVM_GUEST_MODE_SKIP
+        beq     kvmppc_handler_skip_ins
+
         /* Let's store which interrupt we're handling */
         li      r12, \intno
 
@@ -86,6 +91,38 @@ INTERRUPT_TRAMPOLINE	BOOK3S_INTERRUPT_ALTIVEC
 INTERRUPT_TRAMPOLINE    BOOK3S_INTERRUPT_VSX
 
 /*
+ * Bring us back to the faulting code, but skip the
+ * faulting instruction.
+ *
+ * This is a generic exit path from the interrupt
+ * trampolines above.
+ *
+ * Input Registers:
+ *
+ * R12               = free
+ * R13               = PACA
+ * PACA.KVM.SCRATCH0 = guest R12
+ * PACA.KVM.SCRATCH1 = guest CR
+ * SPRG_SCRATCH0     = guest R13
+ *
+ */
+kvmppc_handler_skip_ins:
+
+        /* Patch the IP to the next instruction */
+        mfsrr0  r12
+        addi    r12, r12, 4
+        mtsrr0  r12
+
+        /* Clean up all state */
+        lwz     r12, PACA_KVM_SCRATCH1(r13)
+        mtcr    r12
+        ld      r12, PACA_KVM_SCRATCH0(r13)
+        mfspr   r13, SPRN_SPRG_SCRATCH0
+
+        /* And get back into the code */
+        RFI
+
+/*
  * This trampoline brings us back to a real mode handler
  *
  * Input Registers:
diff --git a/arch/powerpc/kvm/book3s_64_slb.S b/arch/powerpc/kvm/book3s_64_slb.S
index 7188c11ed7d1..d07b88617b2c 100644
--- a/arch/powerpc/kvm/book3s_64_slb.S
+++ b/arch/powerpc/kvm/book3s_64_slb.S
@@ -212,10 +212,6 @@ kvmppc_handler_trampoline_exit:
         mfdar   r5
         mfdsisr r6
 
-        /* Unset guest state */
-        li      r9, 0
-        stb     r9, PACA_KVM_IN_GUEST(r13)
-
         /*
          * In order for us to easily get the last instruction,
          * we got the #vmexit at, we exploit the fact that the
@@ -233,18 +229,28 @@ kvmppc_handler_trampoline_exit:
 
 ld_last_inst:
         /* Save off the guest instruction we're at */
+
+        /* Set guest mode to 'jump over instruction' so if lwz faults
+         * we'll just continue at the next IP. */
+        li      r9, KVM_GUEST_MODE_SKIP
+        stb     r9, PACA_KVM_IN_GUEST(r13)
+
         /*    1) enable paging for data */
         mfmsr   r9
         ori     r11, r9, MSR_DR                 /* Enable paging for data */
         mtmsr   r11
         /*    2) fetch the instruction */
-        /* XXX implement PACA_KVM_IN_GUEST=2 path to safely jump over this */
+        li      r0, KVM_INST_FETCH_FAILED       /* In case lwz faults */
         lwz     r0, 0(r3)
         /*    3) disable paging again */
         mtmsr   r9
 
 no_ld_last_inst:
 
+        /* Unset guest mode */
+        li      r9, KVM_GUEST_MODE_NONE
+        stb     r9, PACA_KVM_IN_GUEST(r13)
+
         /* Restore bolted entries from the shadow and fix it along the way */
 
         /* We don't store anything in entry 0, so we don't need to take care of it */
diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
index 38219af0cd0e..04e317c1bbee 100644
--- a/arch/powerpc/kvm/emulate.c
+++ b/arch/powerpc/kvm/emulate.c
@@ -143,6 +143,10 @@ int kvmppc_emulate_instruction(struct kvm_run *run, struct kvm_vcpu *vcpu)
 
         pr_debug(KERN_INFO "Emulating opcode %d / %d\n", get_op(inst), get_xop(inst));
 
+        /* Try again next time */
+        if (inst == KVM_INST_FETCH_FAILED)
+                return EMULATE_DONE;
+
         switch (get_op(inst)) {
         case OP_TRAP:
 #ifdef CONFIG_PPC64