nitro_enclaves: Handle PCI device command requests

The Nitro Enclaves PCI device exposes a MMIO space that this driver
uses to submit command requests and to receive command replies e.g. for
enclave creation / termination or setting enclave resources.

Add logic for handling PCI device command requests based on the given
command type.

Register an MSI-X interrupt vector for command reply notifications to
handle this type of communication events.

Changelog

v9 -> v10

* Update commit message to include the changelog before the SoB tag(s).

v8 -> v9

* No changes.

v7 -> v8

* Update function signature for submit request and retrive reply
  functions as they only returned 0, no error code.
* Include command type value in the error logs of ne_do_request().

v6 -> v7

* No changes.

v5 -> v6

* Update documentation to kernel-doc format.

v4 -> v5

* Remove sanity checks for situations that shouldn't happen, only if
  buggy system or broken logic at all.

v3 -> v4

* Use dev_err instead of custom NE log pattern.
* Return IRQ_NONE when interrupts are not handled.

v2 -> v3

* Remove the WARN_ON calls.
* Update static calls sanity checks.
* Remove "ratelimited" from the logs that are not in the ioctl call
  paths.

v1 -> v2

* Add log pattern for NE.
* Remove the BUG_ON calls.
* Update goto labels to match their purpose.
* Add fix for kbuild report:
  https://lore.kernel.org/lkml/202004231644.xTmN4Z1z%25lkp@intel.com/

Reviewed-by: Alexander Graf <graf@amazon.com>
Signed-off-by: Alexandru-Catalin Vasile <lexnv@amazon.com>
Signed-off-by: Andra Paraschiv <andraprs@amazon.com>
Link: https://lore.kernel.org/r/20200921121732.44291-6-andraprs@amazon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: andraprs

drivers/virt/nitro_enclaves/ne_pci_dev.c

@@ -33,6 +33,172 @@ static const struct pci_device_id ne_pci_ids[] = {
 
 MODULE_DEVICE_TABLE(pci, ne_pci_ids);
 
+/**
+ * ne_submit_request() - Submit command request to the PCI device based on the
+ *			 command type.
+ * @pdev:		PCI device to send the command to.
+ * @cmd_type:		Command type of the request sent to the PCI device.
+ * @cmd_request:	Command request payload.
+ * @cmd_request_size:	Size of the command request payload.
+ *
+ * Context: Process context. This function is called with the ne_pci_dev mutex held.
+ */
+static void ne_submit_request(struct pci_dev *pdev, enum ne_pci_dev_cmd_type cmd_type,
+			      void *cmd_request, size_t cmd_request_size)
+{
+	struct ne_pci_dev *ne_pci_dev = pci_get_drvdata(pdev);
+
+	memcpy_toio(ne_pci_dev->iomem_base + NE_SEND_DATA, cmd_request, cmd_request_size);
+
+	iowrite32(cmd_type, ne_pci_dev->iomem_base + NE_COMMAND);
+}
+
+/**
+ * ne_retrieve_reply() - Retrieve reply from the PCI device.
+ * @pdev:		PCI device to receive the reply from.
+ * @cmd_reply:		Command reply payload.
+ * @cmd_reply_size:	Size of the command reply payload.
+ *
+ * Context: Process context. This function is called with the ne_pci_dev mutex held.
+ */
+static void ne_retrieve_reply(struct pci_dev *pdev, struct ne_pci_dev_cmd_reply *cmd_reply,
+			      size_t cmd_reply_size)
+{
+	struct ne_pci_dev *ne_pci_dev = pci_get_drvdata(pdev);
+
+	memcpy_fromio(cmd_reply, ne_pci_dev->iomem_base + NE_RECV_DATA, cmd_reply_size);
+}
+
+/**
+ * ne_wait_for_reply() - Wait for a reply of a PCI device command.
+ * @pdev:	PCI device for which a reply is waited.
+ *
+ * Context: Process context. This function is called with the ne_pci_dev mutex held.
+ * Return:
+ * * 0 on success.
+ * * Negative return value on failure.
+ */
+static int ne_wait_for_reply(struct pci_dev *pdev)
+{
+	struct ne_pci_dev *ne_pci_dev = pci_get_drvdata(pdev);
+	int rc = -EINVAL;
+
+	/*
+	 * TODO: Update to _interruptible and handle interrupted wait event
+	 * e.g. -ERESTARTSYS, incoming signals + update timeout, if needed.
+	 */
+	rc = wait_event_timeout(ne_pci_dev->cmd_reply_wait_q,
+				atomic_read(&ne_pci_dev->cmd_reply_avail) != 0,
+				msecs_to_jiffies(NE_DEFAULT_TIMEOUT_MSECS));
+	if (!rc)
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+int ne_do_request(struct pci_dev *pdev, enum ne_pci_dev_cmd_type cmd_type,
+		  void *cmd_request, size_t cmd_request_size,
+		  struct ne_pci_dev_cmd_reply *cmd_reply, size_t cmd_reply_size)
+{
+	struct ne_pci_dev *ne_pci_dev = pci_get_drvdata(pdev);
+	int rc = -EINVAL;
+
+	if (cmd_type <= INVALID_CMD || cmd_type >= MAX_CMD) {
+		dev_err_ratelimited(&pdev->dev, "Invalid cmd type=%u\n", cmd_type);
+
+		return -EINVAL;
+	}
+
+	if (!cmd_request) {
+		dev_err_ratelimited(&pdev->dev, "Null cmd request for cmd type=%u\n",
+				    cmd_type);
+
+		return -EINVAL;
+	}
+
+	if (cmd_request_size > NE_SEND_DATA_SIZE) {
+		dev_err_ratelimited(&pdev->dev, "Invalid req size=%zu for cmd type=%u\n",
+				    cmd_request_size, cmd_type);
+
+		return -EINVAL;
+	}
+
+	if (!cmd_reply) {
+		dev_err_ratelimited(&pdev->dev, "Null cmd reply for cmd type=%u\n",
+				    cmd_type);
+
+		return -EINVAL;
+	}
+
+	if (cmd_reply_size > NE_RECV_DATA_SIZE) {
+		dev_err_ratelimited(&pdev->dev, "Invalid reply size=%zu for cmd type=%u\n",
+				    cmd_reply_size, cmd_type);
+
+		return -EINVAL;
+	}
+
+	/*
+	 * Use this mutex so that the PCI device handles one command request at
+	 * a time.
+	 */
+	mutex_lock(&ne_pci_dev->pci_dev_mutex);
+
+	atomic_set(&ne_pci_dev->cmd_reply_avail, 0);
+
+	ne_submit_request(pdev, cmd_type, cmd_request, cmd_request_size);
+
+	rc = ne_wait_for_reply(pdev);
+	if (rc < 0) {
+		dev_err_ratelimited(&pdev->dev, "Error in wait for reply for cmd type=%u [rc=%d]\n",
+				    cmd_type, rc);
+
+		goto unlock_mutex;
+	}
+
+	ne_retrieve_reply(pdev, cmd_reply, cmd_reply_size);
+
+	atomic_set(&ne_pci_dev->cmd_reply_avail, 0);
+
+	if (cmd_reply->rc < 0) {
+		rc = cmd_reply->rc;
+
+		dev_err_ratelimited(&pdev->dev, "Error in cmd process logic, cmd type=%u [rc=%d]\n",
+				    cmd_type, rc);
+
+		goto unlock_mutex;
+	}
+
+	rc = 0;
+
+unlock_mutex:
+	mutex_unlock(&ne_pci_dev->pci_dev_mutex);
+
+	return rc;
+}
+
+/**
+ * ne_reply_handler() - Interrupt handler for retrieving a reply matching a
+ *			request sent to the PCI device for enclave lifetime
+ *			management.
+ * @irq:	Received interrupt for a reply sent by the PCI device.
+ * @args:	PCI device private data structure.
+ *
+ * Context: Interrupt context.
+ * Return:
+ * * IRQ_HANDLED on handled interrupt.
+ */
+static irqreturn_t ne_reply_handler(int irq, void *args)
+{
+	struct ne_pci_dev *ne_pci_dev = (struct ne_pci_dev *)args;
+
+	atomic_set(&ne_pci_dev->cmd_reply_avail, 1);
+
+	/* TODO: Update to _interruptible. */
+	wake_up(&ne_pci_dev->cmd_reply_wait_q);
+
+	return IRQ_HANDLED;
+}
+
 /**
  * ne_setup_msix() - Setup MSI-X vectors for the PCI device.
  * @pdev:	PCI device to setup the MSI-X for.
@@ -44,6 +210,7 @@ MODULE_DEVICE_TABLE(pci, ne_pci_ids);
  */
 static int ne_setup_msix(struct pci_dev *pdev)
 {
+	struct ne_pci_dev *ne_pci_dev = pci_get_drvdata(pdev);
 	int nr_vecs = 0;
 	int rc = -EINVAL;
 
@@ -63,7 +230,25 @@ static int ne_setup_msix(struct pci_dev *pdev)
 		return rc;
 	}
 
+	/*
+	 * This IRQ gets triggered every time the PCI device responds to a
+	 * command request. The reply is then retrieved, reading from the MMIO
+	 * space of the PCI device.
+	 */
+	rc = request_irq(pci_irq_vector(pdev, NE_VEC_REPLY), ne_reply_handler,
+			 0, "enclave_cmd", ne_pci_dev);
+	if (rc < 0) {
+		dev_err(&pdev->dev, "Error in request irq reply [rc=%d]\n", rc);
+
+		goto free_irq_vectors;
+	}
+
 	return 0;
+
+free_irq_vectors:
+	pci_free_irq_vectors(pdev);
+
+	return rc;
 }
 
 /**
@@ -74,6 +259,10 @@ static int ne_setup_msix(struct pci_dev *pdev)
  */
 static void ne_teardown_msix(struct pci_dev *pdev)
 {
+	struct ne_pci_dev *ne_pci_dev = pci_get_drvdata(pdev);
+
+	free_irq(pci_irq_vector(pdev, NE_VEC_REPLY), ne_pci_dev);
+
 	pci_free_irq_vectors(pdev);
 }