drivers/vfio: EEH support for VFIO PCI device

The patch adds new IOCTL commands for sPAPR VFIO container device
to support EEH functionality for PCI devices, which have been passed
through from host to somebody else via VFIO.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Acked-by: Alexander Graf <agraf@suse.de>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 84 insertions, 3 deletions

diff --git a/Documentation/vfio.txt b/Documentation/vfio.txt
index b9ca023..96978ec 100644
--- a/Documentation/vfio.txt
+++ b/Documentation/vfio.txt
@@ -305,7 +305,15 @@ faster, the map/unmap handling has been implemented in real mode which provides
 an excellent performance which has limitations such as inability to do
 locked pages accounting in real time.
 
-So 3 additional ioctls have been added:
+4) According to sPAPR specification, A Partitionable Endpoint (PE) is an I/O
+subtree that can be treated as a unit for the purposes of partitioning and
+error recovery. A PE may be a single or multi-function IOA (IO Adapter), a
+function of a multi-function IOA, or multiple IOAs (possibly including switch
+and bridge structures above the multiple IOAs). PPC64 guests detect PCI errors
+and recover from them via EEH RTAS services, which works on the basis of
+additional ioctl commands.
+
+So 4 additional ioctls have been added:
 
 	VFIO_IOMMU_SPAPR_TCE_GET_INFO - returns the size and the start
 		of the DMA window on the PCI bus.
@@ -316,9 +324,12 @@ So 3 additional ioctls have been added:
 
 	VFIO_IOMMU_DISABLE - disables the container.
 
+	VFIO_EEH_PE_OP - provides an API for EEH setup, error detection and recovery.
 
 The code flow from the example above should be slightly changed:
 
+	struct vfio_eeh_pe_op pe_op = { .argsz = sizeof(pe_op), .flags = 0 };
+
 	.....
 	/* Add the group to the container */
 	ioctl(group, VFIO_GROUP_SET_CONTAINER, &container);
@@ -342,9 +353,79 @@ The code flow from the example above should be slightly changed:
 	dma_map.flags = VFIO_DMA_MAP_FLAG_READ | VFIO_DMA_MAP_FLAG_WRITE;
 
 	/* Check here is .iova/.size are within DMA window from spapr_iommu_info */
-
 	ioctl(container, VFIO_IOMMU_MAP_DMA, &dma_map);
-	.....
+
+	/* Get a file descriptor for the device */
+	device = ioctl(group, VFIO_GROUP_GET_DEVICE_FD, "0000:06:0d.0");
+
+	....
+
+	/* Gratuitous device reset and go... */
+	ioctl(device, VFIO_DEVICE_RESET);
+
+	/* Make sure EEH is supported */
+	ioctl(container, VFIO_CHECK_EXTENSION, VFIO_EEH);
+
+	/* Enable the EEH functionality on the device */
+	pe_op.op = VFIO_EEH_PE_ENABLE;
+	ioctl(container, VFIO_EEH_PE_OP, &pe_op);
+
+	/* You're suggested to create additional data struct to represent
+	 * PE, and put child devices belonging to same IOMMU group to the
+	 * PE instance for later reference.
+	 */
+
+	/* Check the PE's state and make sure it's in functional state */
+	pe_op.op = VFIO_EEH_PE_GET_STATE;
+	ioctl(container, VFIO_EEH_PE_OP, &pe_op);
+
+	/* Save device state using pci_save_state().
+	 * EEH should be enabled on the specified device.
+	 */
+
+	....
+
+	/* When 0xFF's returned from reading PCI config space or IO BARs
+	 * of the PCI device. Check the PE's state to see if that has been
+	 * frozen.
+	 */
+	ioctl(container, VFIO_EEH_PE_OP, &pe_op);
+
+	/* Waiting for pending PCI transactions to be completed and don't
+	 * produce any more PCI traffic from/to the affected PE until
+	 * recovery is finished.
+	 */
+
+	/* Enable IO for the affected PE and collect logs. Usually, the
+	 * standard part of PCI config space, AER registers are dumped
+	 * as logs for further analysis.
+	 */
+	pe_op.op = VFIO_EEH_PE_UNFREEZE_IO;
+	ioctl(container, VFIO_EEH_PE_OP, &pe_op);
+
+	/*
+	 * Issue PE reset: hot or fundamental reset. Usually, hot reset
+	 * is enough. However, the firmware of some PCI adapters would
+	 * require fundamental reset.
+	 */
+	pe_op.op = VFIO_EEH_PE_RESET_HOT;
+	ioctl(container, VFIO_EEH_PE_OP, &pe_op);
+	pe_op.op = VFIO_EEH_PE_RESET_DEACTIVATE;
+	ioctl(container, VFIO_EEH_PE_OP, &pe_op);
+
+	/* Configure the PCI bridges for the affected PE */
+	pe_op.op = VFIO_EEH_PE_CONFIGURE;
+	ioctl(container, VFIO_EEH_PE_OP, &pe_op);
+
+	/* Restored state we saved at initialization time. pci_restore_state()
+	 * is good enough as an example.
+	 */
+
+	/* Hopefully, error is recovered successfully. Now, you can resume to
+	 * start PCI traffic to/from the affected PE.
+	 */
+
+	....
 
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