linux-kernel - Re: [Qemu-devel] [PATCH v2 2/2] vfio : add aer process

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Message-ID: <20160729111208.2778bfa5@t450s.home>
Date:	Fri, 29 Jul 2016 11:12:08 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Zhou Jie <zhoujie2011@...fujitsu.com>
Cc:	fan.chen@...ystack.cn, linux-kernel@...r.kernel.org,
	qemu-devel@...gnu.org, Chen Fan <chen.fan.fnst@...fujitsu.com>,
	izumi.taku@...fujitsu.com
Subject: Re: [Qemu-devel] [PATCH v2 2/2] vfio : add aer process

On Tue, 19 Jul 2016 15:32:43 +0800
Zhou Jie <zhoujie2011@...fujitsu.com> wrote:

> From: Chen Fan <chen.fan.fnst@...fujitsu.com>
> 
> During aer err occurs and resume do following to
> protect device from being accessed.
> 1. Make config space read only.
> 2. Disable INTx/MSI Interrupt.
> 3. Do nothing for bar regions.
> 
> Signed-off-by: Zhou Jie <zhoujie2011@...fujitsu.com>
> ---
>  drivers/vfio/pci/vfio_pci.c         | 30 ++++++++++++++++++++++++++++++
>  drivers/vfio/pci/vfio_pci_private.h |  2 ++
>  include/uapi/linux/vfio.h           |  2 ++
>  3 files changed, 34 insertions(+)
> 
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index 2d12b03..dd96b60 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -318,6 +318,7 @@ static int vfio_pci_open(void *device_data)
>  		return -ENODEV;
>  
>  	mutex_lock(&driver_lock);
> +	init_completion(&vdev->aer_error_completion);
>  
>  	if (!vdev->refcnt) {
>  		ret = vfio_pci_enable(vdev);
> @@ -571,6 +572,16 @@ static long vfio_pci_ioctl(void *device_data,
>  	struct vfio_pci_device *vdev = device_data;
>  	unsigned long minsz;
>  
> +	if (vdev->aer_error_in_progress && (cmd == VFIO_DEVICE_SET_IRQS ||
> +	    cmd == VFIO_DEVICE_RESET || cmd == VFIO_DEVICE_PCI_HOT_RESET)) {
> +		int ret;
> +		ret = wait_for_completion_interruptible(
> +			&vdev->aer_error_completion);
> +		if (ret) {
> +			return ret;
> +		}

No brackets necessary.

> +	}
> +
>  	if (cmd == VFIO_DEVICE_GET_INFO) {
>  		struct vfio_device_info info;
>  
> @@ -587,6 +598,10 @@ static long vfio_pci_ioctl(void *device_data,
>  		if (vdev->reset_works)
>  			info.flags |= VFIO_DEVICE_FLAGS_RESET;
>  
> +		info.flags |= VFIO_DEVICE_FLAGS_AERPROCESS;
> +		if (vdev->aer_error_in_progress)
> +			info.flags |= VFIO_DEVICE_FLAGS_INAERPROCESS;
> +
>  		info.num_regions = VFIO_PCI_NUM_REGIONS + vdev->num_regions;
>  		info.num_irqs = VFIO_PCI_NUM_IRQS;
>  
> @@ -996,6 +1011,14 @@ static ssize_t vfio_pci_rw(void *device_data, char __user *buf,
>  
>  	switch (index) {
>  	case VFIO_PCI_CONFIG_REGION_INDEX:
> +		if (vdev->aer_error_in_progress && iswrite) {
> +			int ret;
> +			ret = wait_for_completion_interruptible(
> +				&vdev->aer_error_completion);
> +			if (ret) {
> +				return ret;
> +			}
> +		}
>  		return vfio_pci_config_rw(vdev, buf, count, ppos, iswrite);
>  
>  	case VFIO_PCI_ROM_REGION_INDEX:
> @@ -1226,6 +1249,10 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
>  
>  	mutex_lock(&vdev->igate);
>  
> +	vdev->aer_error_in_progress = true;
> +	vfio_pci_set_irqs_ioctl(vdev, VFIO_IRQ_SET_DATA_NONE |
> +				VFIO_IRQ_SET_ACTION_TRIGGER,
> +				vdev->irq_type, 0, 0, NULL);
>  	if (vdev->err_trigger)
>  		eventfd_signal(vdev->err_trigger, 1);
>  
> @@ -1252,6 +1279,9 @@ static void vfio_pci_aer_resume(struct pci_dev *pdev)
>  	}
>  
>  	mutex_lock(&vdev->igate);
> +
> +	vdev->aer_error_in_progress = false;
> +	complete_all(&vdev->aer_error_completion);
>  	if (vdev->resume_trigger)
>  		eventfd_signal(vdev->resume_trigger, 1);
>  
> diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
> index 80d4ddd..2f151f5 100644
> --- a/drivers/vfio/pci/vfio_pci_private.h
> +++ b/drivers/vfio/pci/vfio_pci_private.h
> @@ -84,6 +84,8 @@ struct vfio_pci_device {
>  	bool			has_vga;
>  	bool			needs_reset;
>  	bool			nointx;
> +	bool			aer_error_in_progress;
> +	struct completion	aer_error_completion;
>  	struct pci_saved_state	*pci_saved_state;
>  	int			refcnt;
>  	struct eventfd_ctx	*err_trigger;
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 34ab138..276ce50 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -198,6 +198,8 @@ struct vfio_device_info {
>  #define VFIO_DEVICE_FLAGS_PCI	(1 << 1)	/* vfio-pci device */
>  #define VFIO_DEVICE_FLAGS_PLATFORM (1 << 2)	/* vfio-platform device */
>  #define VFIO_DEVICE_FLAGS_AMBA  (1 << 3)	/* vfio-amba device */
> +#define VFIO_DEVICE_FLAGS_AERPROCESS  (1 << 4)	/* support aer error progress */
> +#define VFIO_DEVICE_FLAGS_INAERPROCESS  (1 << 5)/* status in aer error progress */
>  	__u32	num_regions;	/* Max region index + 1 */
>  	__u32	num_irqs;	/* Max IRQ index + 1 */
>  };

Clearly this has only been tested for a single instance of an AER error
event and resume per device.  Are the things you're intending to block
actually blocked for subsequent events?  Note how complete_all() fills
the done field to let all current and future waiters go through and
nowhere is there a call to reinit_completion() to drain that path.
Thanks,

Alex