linux-kernel - Re: [PATCH] vfio: Add an ioctl to reset the device

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Message-Id: <20110419144023.4d3f61da.rdunlap@xenotime.net>
Date:	Tue, 19 Apr 2011 14:40:23 -0700
From:	Randy Dunlap <rdunlap@...otime.net>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	pugs@...e.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, qemu-devel@...gnu.org,
	chrisw@...hat.com, aafabbri@...co.com, dwang2@...co.com,
	benve@...co.com
Subject: Re: [PATCH] vfio: Add an ioctl to reset the device

On Tue, 19 Apr 2011 14:32:59 -0600 Alex Williamson wrote:

> 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@...hat.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

I can't find include/linux/vfio.h in linux-next or mainline git, but
ioctls need to be documented in Documentation/ioctl/ioctl-number.txt....

---
~Randy
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