[Qemu-devel] [PATCH] vfio: Add an ioctl to reset the device

[Alex Williamson <alex.williamson@redhat.com>]

When using VFIO to assign a device to a guest, we want to make sure
the device is quiesced on VM reset to stop all DMA within the guest
mapped memory.  Add an ioctl which just calls pci_reset_function()
and returns whether it succeeds.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

We've recently needed to add this functionality for current KVM
based device assignment, VFIO should provide a way to do this too.
An example of it being used in the Qemu VFIO driver can be found
here:

https://github.com/awilliam/qemu-vfio/blob/vfio/hw/vfio.c

 drivers/vfio/vfio_main.c |    4 ++++
 include/linux/vfio.h     |    3 +++
 2 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index 7e427fc..b9bb692 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -490,6 +490,10 @@ static long vfio_unl_ioctl(struct file *filep,
 		ret = vfio_irq_eoi_eventfd(vdev, fd);
 		break;
 
+	case VFIO_RESET_FUNCTION:
+		ret = pci_reset_function(vdev->pdev);
+		break;
+
 	default:
 		return -EINVAL;
 	}
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index f07d8fe..47d9bb9 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -215,6 +215,9 @@ struct vfio_dma_map {
 /* Re-enable INTx via eventfd */
 #define	VFIO_IRQ_EOI_EVENTFD	_IOW(';', 110, int)
 
+/* Reset PCI function */
+#define VFIO_RESET_FUNCTION	_IO(';', 111)
+
 /*
  * Reads, writes, and mmaps determine which PCI BAR (or config space)
  * from the high level bits of the file offset