2 files changed, 23 insertions, 11 deletions

diff --git a/arch/powerpc/kvm/book3s_hv_ras.c b/arch/powerpc/kvm/book3s_hv_ras.c
index 768a9f977c00..3a5c568b1e89 100644
--- a/arch/powerpc/kvm/book3s_hv_ras.c
+++ b/arch/powerpc/kvm/book3s_hv_ras.c
@@ -113,10 +113,8 @@ static long kvmppc_realmode_mc_power7(struct kvm_vcpu *vcpu)
          * We assume that if the condition is recovered then linux host
          * will have generated an error log event that we will pick
          * up and log later.
-         * Don't release mce event now. In case if condition is not
-         * recovered we do guest exit and go back to linux host machine
-         * check handler. Hence we need make sure that current mce event
-         * is available for linux host to consume.
+         * Don't release mce event now. We will queue up the event so that
+         * we can log the MCE event info on host console.
          */
         if (!get_mce_event(&mce_evt, MCE_EVENT_DONTRELEASE))
                 goto out;
@@ -128,11 +126,12 @@ static long kvmppc_realmode_mc_power7(struct kvm_vcpu *vcpu)
 
 out:
         /*
-         * If we have handled the error, then release the mce event because
-         * we will be delivering machine check to guest.
+         * We are now going enter guest either through machine check
+         * interrupt (for unhandled errors) or will continue from
+         * current HSRR0 (for handled errors) in guest. Hence
+         * queue up the event so that we can log it from host console later.
          */
-        if (handled)
-                release_mce_event();
+        machine_check_queue_event();
 
         return handled;
 }
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 77356fd25ccc..868347ef09fd 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -2257,15 +2257,28 @@ machine_check_realmode:
         mr      r3, r9          /* get vcpu pointer */
         bl      kvmppc_realmode_machine_check
         nop
-        cmpdi   r3, 0           /* continue exiting from guest? */
+        cmpdi   r3, 0           /* Did we handle MCE ? */
         ld      r9, HSTATE_KVM_VCPU(r13)
         li      r12, BOOK3S_INTERRUPT_MACHINE_CHECK
-        beq     mc_cont
+        /*
+         * Deliver unhandled/fatal (e.g. UE) MCE errors to guest through
+         * machine check interrupt (set HSRR0 to 0x200). And for handled
+         * errors (no-fatal), just go back to guest execution with current
+         * HSRR0 instead of exiting guest. This new approach will inject
+         * machine check to guest for fatal error causing guest to crash.
+         *
+         * The old code used to return to host for unhandled errors which
+         * was causing guest to hang with soft lockups inside guest and
+         * makes it difficult to recover guest instance.
+         */
+        ld      r10, VCPU_PC(r9)
+        ld      r11, VCPU_MSR(r9)
+        bne     2f      /* Continue guest execution. */
         /* If not, deliver a machine check.  SRR0/1 are already set */
         li      r10, BOOK3S_INTERRUPT_MACHINE_CHECK
         ld      r11, VCPU_MSR(r9)
         bl      kvmppc_msr_interrupt
-        b       fast_interrupt_c_return
+2:      b       fast_interrupt_c_return
 
 /*
  * Check the reason we woke from nap, and take appropriate action.