KVM: s390: Add FAULT_FLAG_RETRY_NOWAIT for guest fault

In the case of a fault, we will retry to exit sie64 but with gmap fault
indication for this thread set. This makes it possible to handle async
page faults.

Based on a patch from Martin Schwidefsky.

Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

1 files changed, 21 insertions, 2 deletions

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 782420f3c4d5..9eec794caa7f 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -255,6 +255,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
                 if (!kvm->arch.gmap)
                         goto out_nogmap;
                 kvm->arch.gmap->private = kvm;
+                kvm->arch.gmap->pfault_enabled = 0;
         }
 
         kvm->arch.css_support = 0;
@@ -701,6 +702,17 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
         return 0;
 }
 
+static long kvm_arch_fault_in_sync(struct kvm_vcpu *vcpu)
+{
+        long rc;
+        hva_t fault = gmap_fault(current->thread.gmap_addr, vcpu->arch.gmap);
+        struct mm_struct *mm = current->mm;
+        down_read(&mm->mmap_sem);
+        rc = get_user_pages(current, mm, fault, 1, 1, 0, NULL, NULL);
+        up_read(&mm->mmap_sem);
+        return rc;
+}
+
 static int vcpu_pre_run(struct kvm_vcpu *vcpu)
 {
         int rc, cpuflags;
@@ -730,7 +742,7 @@ static int vcpu_pre_run(struct kvm_vcpu *vcpu)
 
 static int vcpu_post_run(struct kvm_vcpu *vcpu, int exit_reason)
 {
-        int rc;
+        int rc = -1;
 
         VCPU_EVENT(vcpu, 6, "exit sie icptcode %d",
                    vcpu->arch.sie_block->icptcode);
@@ -744,7 +756,14 @@ static int vcpu_post_run(struct kvm_vcpu *vcpu, int exit_reason)
                                                 current->thread.gmap_addr;
                 vcpu->run->s390_ucontrol.pgm_code = 0x10;
                 rc = -EREMOTE;
-        } else {
+
+        } else if (current->thread.gmap_pfault) {
+                current->thread.gmap_pfault = 0;
+                if (kvm_arch_fault_in_sync(vcpu) >= 0)
+                        rc = 0;
+        }
+
+        if (rc == -1) {
                 VCPU_EVENT(vcpu, 3, "%s", "fault in sie instruction");
                 trace_kvm_s390_sie_fault(vcpu);
                 rc = kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);