KVM: s390: move kvm_guest_enter,exit closer to sie

commit 2b29a9fdcb92bfc6b6f4c412d71505869de61a56 upstream.

Any uaccess between guest_enter and guest_exit could trigger a page fault,
the page fault handler would handle it as a guest fault and translate a
user address as guest address.

Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 14 insertions, 7 deletions

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index c1c7c683fa26..698fb826e149 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -622,14 +622,25 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
                 kvm_s390_deliver_pending_interrupts(vcpu);
 
         vcpu->arch.sie_block->icptcode = 0;
-        preempt_disable();
-        kvm_guest_enter();
-        preempt_enable();
         VCPU_EVENT(vcpu, 6, "entering sie flags %x",
                    atomic_read(&vcpu->arch.sie_block->cpuflags));
         trace_kvm_s390_sie_enter(vcpu,
                                  atomic_read(&vcpu->arch.sie_block->cpuflags));
+
+        /*
+         * As PF_VCPU will be used in fault handler, between guest_enter
+         * and guest_exit should be no uaccess.
+         */
+        preempt_disable();
+        kvm_guest_enter();
+        preempt_enable();
         rc = sie64a(vcpu->arch.sie_block, vcpu->run->s.regs.gprs);
+        kvm_guest_exit();
+
+        VCPU_EVENT(vcpu, 6, "exit sie icptcode %d",
+                   vcpu->arch.sie_block->icptcode);
+        trace_kvm_s390_sie_exit(vcpu, vcpu->arch.sie_block->icptcode);
+
         if (rc) {
                 if (kvm_is_ucontrol(vcpu->kvm)) {
                         rc = SIE_INTERCEPT_UCONTROL;
@@ -639,10 +650,6 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
                         rc = kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
                 }
         }
-        VCPU_EVENT(vcpu, 6, "exit sie icptcode %d",
-                   vcpu->arch.sie_block->icptcode);
-        trace_kvm_s390_sie_exit(vcpu, vcpu->arch.sie_block->icptcode);
-        kvm_guest_exit();
 
         memcpy(&vcpu->run->s.regs.gprs[14], &vcpu->arch.sie_block->gg14, 16);
         return rc;