On 05/11/2018 12:08 PM, Halil Pasic wrote:
On 05/07/2018 05:11 PM, Tony Krowiak wrote:
Provides interfaces to manage the AP adapters, usage domains
and control domains assigned to a KVM guest.
The guest's SIE state description has a satellite structure called the
Crypto Control Block (CRYCB) containing three bitmask fields
identifying the adapters, queues (domains) and control domains
assigned to the KVM guest:
[..]
index 00bcfb0..98b53c7 100644
--- a/arch/s390/kvm/kvm-ap.c
+++ b/arch/s390/kvm/kvm-ap.c
@@ -7,6 +7,7 @@
[..]
+
+/**
+ * kvm_ap_validate_queue_sharing
+ *
+ * Verifies that the APQNs derived from the cross product of the AP
adapter IDs
+ * and AP queue indexes comprising the AP matrix are not configured for
+ * another guest. AP queue sharing is not allowed.
+ *
+ * @kvm: the KVM guest
+ * @matrix: the AP matrix
+ *
+ * Returns 0 if the APQNs are valid, otherwise; returns -EBUSY.
+ */
+static int kvm_ap_validate_queue_sharing(struct kvm *kvm,
+ struct kvm_ap_matrix *matrix)
+{
+ struct kvm *vm;
+ unsigned long *apm, *aqm;
+ unsigned long apid, apqi;
+
+
+ /* No other VM may share an AP Queue with the input VM */
+ list_for_each_entry(vm, &vm_list, vm_list) {
+ if (kvm == vm)
+ continue;
+
+ apm = kvm_ap_get_crycb_apm(vm);
+ if (!bitmap_and(apm, apm, matrix->apm, matrix->apm_max + 1))
+ continue;
+
+ aqm = kvm_ap_get_crycb_aqm(vm);
+ if (!bitmap_and(aqm, aqm, matrix->aqm, matrix->aqm_max + 1))
+ continue;
+
+ for_each_set_bit_inv(apid, apm, matrix->apm_max + 1)
+ for_each_set_bit_inv(apqi, aqm, matrix->aqm_max + 1)
+ kvm_ap_log_sharing_err(vm, apid, apqi);
+
+ return -EBUSY;
+ }
+
+ return 0;
+}
+
+int kvm_ap_configure_matrix(struct kvm *kvm, struct kvm_ap_matrix
*matrix)
+{
+ int ret = 0;
+
+ mutex_lock(&kvm->lock);
You seem to take only kvm->lock, vm_list however (used in
kvm_ap_validate_queue_sharing()) seems to be protected by
kvm_lock.
Can you tell me why is this supposed to be safe?
What is supposed to prevent an execution like
vm1: call kvm_ap_configure_matrix(m1)
vm2: call kvm_ap_configure_matrix(m2)
vm1: call kvm_ap_validate_queue_sharing(m1)
vm2: call kvm_ap_validate_queue_sharing(m2)
vm1: call kvm_ap_set_crycb_masks(m1)
vm2: call kvm_ap_set_crycb_masks(m2)
where, let's say, m1 and m2 are equal in the sense that the
mask values are the same?
vm1 will get the kvm->lock first in your scenario when
kvm_ap_configure_matrix(m1) is invoked. Since the other
functions - i.e., kvm_ap_validate_queue_sharing(m1) and
kvm_ap_set_crycb_masks(m1) - are static and only called
from the kvm_ap_configure_matrix(m1), your scenario
can never happen because vm2 will not get the lock until
kvm_ap_configure_matrix(m1) has completed. I see your
point, however, and maybe I should also acquire the kvm_lock.
Regards,
Halil
+
+ ret = kvm_ap_validate_queue_sharing(kvm, matrix);
+ if (ret)
+ goto done;
+
+ kvm_ap_set_crycb_masks(kvm, matrix);
+
+done:
+ mutex_unlock(&kvm->lock);
+
+ return ret;
+}
+EXPORT_SYMBOL(kvm_ap_configure_matrix);
+
