From 931f261b42f10c8c8c9ab53f5ceb47ce51af7cf5 Mon Sep 17 00:00:00 2001
From: Andrea Arcangeli <aarcange@redhat.com>
Date: Sat, 17 Dec 2016 18:43:52 +0100
Subject: [PATCH] kvm: fix schedule in atomic in kvm_steal_time_set_preempted()
kvm_steal_time_set_preempted() isn't disabling the pagefaults before
calling __copy_to_user and the kernel debug notices.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/x86.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 49da1064ef50..8ce1139a08b5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2844,7 +2844,17 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
+ /*
+ * Disable page faults because we're in atomic context here.
+ * kvm_write_guest_offset_cached() would call might_fault()
+ * that relies on pagefault_disable() to tell if there's a
+ * bug. NOTE: the write to guest memory may not go through if
+ * during postcopy live migration or if there's heavy guest
+ * paging.
+ */
+ pagefault_disable();
kvm_steal_time_set_preempted(vcpu);
+ pagefault_enable();
kvm_x86_ops->vcpu_put(vcpu);
kvm_put_guest_fpu(vcpu);
vcpu->arch.last_host_tsc = rdtsc();
--
GitLab