Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm fixes from Paolo Bonzini:

 - Fixes for s390 interrupt delivery

 - Fixes for Xen emulator bugs showing up as debug kernel WARNs

 - Fix another issue with SEV/ES string I/O VMGEXITs

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: x86: Take srcu lock in post_kvm_run_save()
  KVM: SEV-ES: fix another issue with string I/O VMGEXITs
  KVM: x86/xen: Fix kvm_xen_has_interrupt() sleeping in kvm_vcpu_block()
  KVM: x86: switch pvclock_gtod_sync_lock to a raw spinlock
  KVM: s390: preserve deliverable_mask in __airqs_kick_single_vcpu
  KVM: s390: clear kicked_mask before sleeping again

1 files changed, 22 insertions, 5 deletions

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 9ea9c3dabe37..8f62baebd028 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -190,6 +190,7 @@ void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, int state)
 
 int __kvm_xen_has_interrupt(struct kvm_vcpu *v)
 {
+	int err;
 	u8 rc = 0;
 
 	/*
@@ -216,13 +217,29 @@ int __kvm_xen_has_interrupt(struct kvm_vcpu *v)
 	if (likely(slots->generation == ghc->generation &&
 		   !kvm_is_error_hva(ghc->hva) && ghc->memslot)) {
 		/* Fast path */
-		__get_user(rc, (u8 __user *)ghc->hva + offset);
-	} else {
-		/* Slow path */
-		kvm_read_guest_offset_cached(v->kvm, ghc, &rc, offset,
-					     sizeof(rc));
+		pagefault_disable();
+		err = __get_user(rc, (u8 __user *)ghc->hva + offset);
+		pagefault_enable();
+		if (!err)
+			return rc;
 	}
 
+	/* Slow path */
+
+	/*
+	 * This function gets called from kvm_vcpu_block() after setting the
+	 * task to TASK_INTERRUPTIBLE, to see if it needs to wake immediately
+	 * from a HLT. So we really mustn't sleep. If the page ended up absent
+	 * at that point, just return 1 in order to trigger an immediate wake,
+	 * and we'll end up getting called again from a context where we *can*
+	 * fault in the page and wait for it.
+	 */
+	if (in_atomic() || !task_is_running(current))
+		return 1;
+
+	kvm_read_guest_offset_cached(v->kvm, ghc, &rc, offset,
+				     sizeof(rc));
+
 	return rc;
 }