[RFC PATCH V2 18/18] vfio/pci: Support IMS cookie modification

[Reinette Chatre]

IMS supports an implementation specific cookie that is associated
with each interrupt. By default the IMS interrupt allocation backend
will assign a default cookie to a new interrupt instance.

Add support for a virtual device driver to set the interrupt instance
specific cookie. For example, the virtual device driver may intercept
the guest's MMIO write that configuresa a new PASID for a particular
interrupt. Calling vfio_pci_ims_set_cookie() with the new PASID value
as IMS cookie enables subsequent interrupts to be allocated with
accurate data.

Signed-off-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
---
 drivers/vfio/pci/vfio_pci_intrs.c | 53 +++++++++++++++++++++++++++++++
 include/linux/vfio_pci_core.h     |  3 ++
 2 files changed, 56 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index df458aed2175..e9e46633af65 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -1228,6 +1228,59 @@ int vfio_pci_ims_hwirq(struct vfio_pci_intr_ctx *intr_ctx, unsigned int vector)
 }
 EXPORT_SYMBOL_GPL(vfio_pci_ims_hwirq);
 
+/*
+ * vfio_pci_ims_set_cookie() - Set unique cookie for vector.
+ * @intr_ctx:	Interrupt context.
+ * @vector:	Vector.
+ * @icookie:	New cookie for @vector.
+ *
+ * When new IMS interrupt is allocated for @vector it will be
+ * assigned @icookie.
+ */
+int vfio_pci_ims_set_cookie(struct vfio_pci_intr_ctx *intr_ctx,
+			    unsigned int vector,
+			    union msi_instance_cookie *icookie)
+{
+	struct vfio_pci_irq_ctx *ctx;
+	int ret = -EINVAL;
+
+	mutex_lock(&intr_ctx->igate);
+
+	if (!intr_ctx->ims_backed_irq)
+		goto out_unlock;
+
+	ctx = vfio_irq_ctx_get(intr_ctx, vector);
+	if (ctx) {
+		if (WARN_ON_ONCE(ctx->emulated)) {
+			ret = -EINVAL;
+			goto out_unlock;
+		}
+		ctx->icookie = *icookie;
+		ret = 0;
+		goto out_unlock;
+	}
+
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
+	if (!ctx) {
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
+
+	ctx->icookie = *icookie;
+	ret = xa_insert(&intr_ctx->ctx, vector, ctx, GFP_KERNEL_ACCOUNT);
+	if (ret) {
+		kfree(ctx);
+		goto out_unlock;
+	}
+
+	ret = 0;
+
+out_unlock:
+	mutex_unlock(&intr_ctx->igate);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(vfio_pci_ims_set_cookie);
+
 int vfio_pci_set_irqs_ioctl(struct vfio_pci_intr_ctx *intr_ctx, uint32_t flags,
 			    unsigned int index, unsigned int start,
 			    unsigned int count, void *data)
diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
index c6e399b39e90..32c2145ffdb5 100644
--- a/include/linux/vfio_pci_core.h
+++ b/include/linux/vfio_pci_core.h
@@ -168,6 +168,9 @@ int vfio_pci_ims_init_intr_ctx(struct vfio_device *vdev,
 			       struct pci_dev *pdev,
 			       union msi_instance_cookie *default_cookie);
 int vfio_pci_ims_hwirq(struct vfio_pci_intr_ctx *intr_ctx, unsigned int vector);
+int vfio_pci_ims_set_cookie(struct vfio_pci_intr_ctx *intr_ctx,
+			    unsigned int vector,
+			    union msi_instance_cookie *icookie);
 void vfio_pci_ims_release_intr_ctx(struct vfio_pci_intr_ctx *intr_ctx);
 void vfio_pci_send_signal(struct vfio_pci_intr_ctx *intr_ctx, unsigned int vector);
 int vfio_pci_set_emulated(struct vfio_pci_intr_ctx *intr_ctx,
-- 
2.34.1