Re: [PATCH v4 5/7] s390: ap: implement PAPQ AQIC interception in kernel
From: Pierre Morel
Date: Mon Mar 04 2019 - 04:47:34 EST
On 04/03/2019 02:57, Halil Pasic wrote:
On Fri, 22 Feb 2019 16:29:58 +0100
Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:
We register the AP PQAP instruction hook during the open
of the mediated device. And unregister it on release.
In the AP PQAP instruction hook, if we receive a demand to
enable IRQs,
- we retrieve the vfio_ap_queue based on the APQN we receive
in REG1,
- we retrieve the page of the guest address, (NIB), from
register REG2
- we the mediated device to use the VFIO pinning infratrsucture
to pin the page of the guest address,
- we retrieve the pointer to KVM to register the guest ISC
and retrieve the host ISC
- finaly we activate GISA
If we receive a demand to disable IRQs,
- we deactivate GISA
- unregister from the GIB
- unping the NIB
Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
[..]
+ */
+static void vfio_ap_free_irq(struct vfio_ap_queue *q)
+{
+ if (!q)
+ return;
+ if (q->g_pfn)
+ vfio_unpin_pages(mdev_dev(q->matrix_mdev->mdev), &q->g_pfn, 1);
+ if (q->isc)
+ kvm_s390_gisc_unregister(q->matrix_mdev->kvm, q->isc);
Ain't isc 0 a perfectly legit isc?
Exact, even GIB interface always gives 5 back I should initialize the
ISC to a bad value like > 7
Will do, thanks.
+ q->nib = 0;
+ q->isc = 0;
+ q->g_pfn = 0;
+}
+
[..]
@@ -109,10 +131,16 @@ static int vfio_ap_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
static int vfio_ap_mdev_remove(struct mdev_device *mdev)
{
struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev);
+ struct vfio_ap_queue *q, *qtmp;
if (matrix_mdev->kvm)
return -EBUSY;
+ list_for_each_entry_safe(q, qtmp, &matrix_mdev->qlist, list) {
+ q->matrix_mdev = NULL;
+ vfio_ap_mdev_reset_queue(q);
+ list_move(&q->list, &matrix_dev->free_list);
How about matrix_dev->lock? I guess you should protect free_list with
it. If not maybe a code comment would help not stumble over this.
Conny already commented that I forgot locks
I need a lock there and in the interception. May be more, I will check.
+ }
mutex_lock(&matrix_dev->lock);
list_del(&matrix_mdev->node);
mutex_unlock(&matrix_dev->lock);
[..]
+/**
+ * vfio_ap_setirq: Enable Interruption for a APQN
+ *
+ * @dev: the device associated with the ap_queue
+ * @q: the vfio_ap_queue holding AQIC parameters
+ *
+ * Pin the NIB saved in *q
+ * Register the guest ISC to GIB interface and retrieve the
+ * host ISC to issue the host side PQAP/AQIC
+ *
+ * Response.status may be set to following Response Code in case of error:
+ * - AP_RESPONSE_INVALID_ADDRESS: vfio_pin_pages failed
+ * - AP_RESPONSE_OTHERWISE_CHANGED: Hypervizor GISA internal error
+ *
+ * Otherwise return the ap_queue_status returned by the ap_aqic()
+ */
+static struct ap_queue_status vfio_ap_setirq(struct vfio_ap_queue *q)
+{
+ struct ap_qirq_ctrl aqic_gisa = {};
+ struct ap_queue_status status = {};
+ struct kvm_s390_gisa *gisa;
+ struct kvm *kvm;
+ unsigned long g_pfn, h_nib, h_pfn;
+ int ret;
+
+ kvm = q->matrix_mdev->kvm;
+ gisa = kvm->arch.gisa_int.origin;
+
+ g_pfn = q->nib >> PAGE_SHIFT;
+ ret = vfio_pin_pages(mdev_dev(q->matrix_mdev->mdev), &g_pfn, 1,
+ IOMMU_READ | IOMMU_WRITE, &h_pfn);
+ switch (ret) {
+ case 1:
+ break;
+ case -EINVAL:
+ case -E2BIG:
+ status.response_code = AP_RESPONSE_INVALID_ADDRESS;
+ /* Fallthrough */
+ default:
+ return status;
+ }
+
+ h_nib = (h_pfn << PAGE_SHIFT) | (q->nib & ~PAGE_MASK);
+ aqic_gisa.gisc = q->isc;
+ aqic_gisa.isc = kvm_s390_gisc_register(kvm, q->isc);
+ aqic_gisa.ir = 1;
+ aqic_gisa.gisa = gisa->next_alert >> 4;
+
+ status = ap_aqic(q->apqn, aqic_gisa, (void *)h_nib);
+ switch (status.response_code) {
+ case AP_RESPONSE_NORMAL:
+ if (q->g_pfn)
+ vfio_unpin_pages(mdev_dev(q->matrix_mdev->mdev),
+ &q->g_pfn, 1);
Shouldn't you call kvm_s390_gisc_unregister() here.
I should.
+ q->g_pfn = g_pfn;
+ break;
+ case AP_RESPONSE_OTHERWISE_CHANGED:
+ vfio_unpin_pages(mdev_dev(q->matrix_mdev->mdev), &g_pfn, 1);
and here.
too
+ break;
+ case AP_RESPONSE_INVALID_GISA:
+ status.response_code = AP_RESPONSE_INVALID_ADDRESS;
+ default: /* Fall Through */
+ pr_warn("%s: apqn %04x: response: %02x\n", __func__, q->apqn,
+ status.response_code);
+ vfio_ap_free_irq(q);
This guy won't unpin g_pfn but only q->g_pfn if not zero :/
OK, seems I have to rework this all.
Thanks.
+ break;
+ }
+
+ return status;
+}
+
+/**
+ * handle_pqap: PQAP instruction callback
+ *
+ * @vcpu: The vcpu on which we received the PQAP instruction
+ *
+ * Get the general register contents to initialize internal variables.
+ * REG[0]: APQN
+ * REG[1]: IR and ISC
+ * REG[2]: NIB
+ *
+ * Response.status may be set to following Response Code:
+ * - AP_RESPONSE_Q_NOT_AVAIL: if the queue is not available
+ * - AP_RESPONSE_DECONFIGURED: if the queue is not configured
+ * - AP_RESPONSE_NORMAL (0) : in case of successs
+ * Check vfio_ap_setirq() and vfio_ap_clrirq() for other possible
RC.
+ *
+ * Return 0 if we could handle the request inside KVM.
+ * otherwise, returns -EOPNOTSUPP to let QEMU handle the fault.
+ */
+static int handle_pqap(struct kvm_vcpu *vcpu)
+{
+ uint64_t status;
+ uint16_t apqn;
+ struct vfio_ap_queue *q;
+ struct ap_queue_status qstatus = {};
+ struct ap_matrix_mdev *matrix_mdev;
+
+ /* If we do not use the AIV facility just go to userland */
+ if (!(vcpu->arch.sie_block->eca & ECA_AIV))
+ return -EOPNOTSUPP;
+
+ apqn = vcpu->run->s.regs.gprs[0] & 0xffff;
+ matrix_mdev = vcpu->kvm->arch.crypto.vfio_private;
+ if (!matrix_mdev)
+ return -EOPNOTSUPP;
+ q = vfio_ap_get_queue(apqn, &matrix_mdev->qlist);
This get is not a 'refcount affecting get' any more...
+ if (!q) {
+ qstatus.response_code = AP_RESPONSE_Q_NOT_AVAIL;
+ goto out;
+ }
+
+ status = vcpu->run->s.regs.gprs[1];
+
+ /* If IR bit(16) is set we enable the interrupt */
+ if ((status >> (63 - 16)) & 0x01) {
+ q->isc = status & 0x07;
+ q->nib = vcpu->run->s.regs.gprs[2];
... and I don't see what should prevent a potential use after free here.
I think this will be corrected when I add the lock I forgot in handle_pqap.
Thanks for the comments,
Regards,
Pierre
--
Pierre Morel
Linux/KVM/QEMU in BÃblingen - Germany