Re: [LINUX KERNEL PATCH v5 1/2] virtio_pci: Add freeze_mode for virtio_pci_common_cfg

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Sep 19, 2023 at 06:46:06PM +0800, Jiqian Chen wrote:
> When guest vm does S3, Qemu will reset and clear some things of virtio
> devices, but guest can't aware that, so that may cause some problems.
> For excample, Qemu calls virtio_reset->virtio_gpu_gl_reset, that will
> destroy render resources of virtio-gpu. As a result, after guest resume,
> the display can't come back and we only saw a black screen. Due to guest
> can't re-create all the resources, so we need to let Qemu not to destroy
> them when S3.
> 
> For above purpose, this patch add a new parameter named freeze_mode to
> struct virtio_pci_common_cfg, and when guest suspends, it can set
> freeze_mode to be FREEZE_S3, so that virtio devices can change their
> reset behavior on Qemu side according to that mode.
> 
> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
> ---
>  drivers/virtio/virtio.c                | 13 +++++++++++++
>  drivers/virtio/virtio_pci_modern.c     |  9 +++++++++
>  drivers/virtio/virtio_pci_modern_dev.c | 16 ++++++++++++++++
>  include/linux/virtio_config.h          |  1 +
>  include/linux/virtio_pci_modern.h      |  2 ++
>  include/uapi/linux/virtio_pci.h        | 16 ++++++++++++++--
>  6 files changed, 55 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index 3893dc29eb26..b4eb8369d5a1 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -7,6 +7,7 @@
>  #include <linux/idr.h>
>  #include <linux/of.h>
>  #include <uapi/linux/virtio_ids.h>
> +#include <uapi/linux/virtio_pci.h>
>  
>  /* Unique numbering for virtio devices. */
>  static DEFINE_IDA(virtio_index_ida);
> @@ -486,10 +487,20 @@ void unregister_virtio_device(struct virtio_device *dev)
>  EXPORT_SYMBOL_GPL(unregister_virtio_device);
>  
>  #ifdef CONFIG_PM_SLEEP
> +static void virtio_set_freeze_mode(struct virtio_device *dev, u16 mode)
> +{
> +	if (!dev->config->set_freeze_mode)
> +		return;
> +	might_sleep();
> +	dev->config->set_freeze_mode(dev, mode);
> +}
> +
>  int virtio_device_freeze(struct virtio_device *dev)
>  {
>  	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
>  
> +	virtio_set_freeze_mode(dev, VIRTIO_PCI_FREEZE_MODE_FREEZE_S3);
> +
>  	virtio_config_disable(dev);
>  
>  	dev->failed = dev->config->get_status(dev) & VIRTIO_CONFIG_S_FAILED;
> @@ -544,6 +555,8 @@ int virtio_device_restore(struct virtio_device *dev)
>  
>  	virtio_config_enable(dev);
>  
> +	virtio_set_freeze_mode(dev, VIRTIO_PCI_FREEZE_MODE_UNFREEZE);
> +
>  	return 0;
>  
>  err:
> diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> index d6bb68ba84e5..846b70919cbd 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -491,6 +491,13 @@ static bool vp_get_shm_region(struct virtio_device *vdev,
>  	return true;
>  }
>  
> +static void vp_set_freeze_mode(struct virtio_device *vdev, u16 mode)
> +{
> +	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
> +
> +	vp_modern_set_freeze_mode(&vp_dev->mdev, mode);
> +}
> +
>  static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
>  	.get		= NULL,
>  	.set		= NULL,
> @@ -509,6 +516,7 @@ static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
>  	.get_shm_region  = vp_get_shm_region,
>  	.disable_vq_and_reset = vp_modern_disable_vq_and_reset,
>  	.enable_vq_after_reset = vp_modern_enable_vq_after_reset,
> +	.set_freeze_mode = vp_set_freeze_mode,
>  };
>  
>  static const struct virtio_config_ops virtio_pci_config_ops = {
> @@ -529,6 +537,7 @@ static const struct virtio_config_ops virtio_pci_config_ops = {
>  	.get_shm_region  = vp_get_shm_region,
>  	.disable_vq_and_reset = vp_modern_disable_vq_and_reset,
>  	.enable_vq_after_reset = vp_modern_enable_vq_after_reset,
> +	.set_freeze_mode = vp_set_freeze_mode,
>  };
>  
>  /* the PCI probing function */
> diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
> index aad7d9296e77..4a6f7d130b6e 100644
> --- a/drivers/virtio/virtio_pci_modern_dev.c
> +++ b/drivers/virtio/virtio_pci_modern_dev.c
> @@ -203,6 +203,8 @@ static inline void check_offsets(void)
>  		     offsetof(struct virtio_pci_common_cfg, queue_used_lo));
>  	BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_USEDHI !=
>  		     offsetof(struct virtio_pci_common_cfg, queue_used_hi));
> +	BUILD_BUG_ON(VIRTIO_PCI_COMMON_F_MODE !=
> +		     offsetof(struct virtio_pci_common_cfg, freeze_mode));
>  }
>  
>  /*
> @@ -714,6 +716,20 @@ void __iomem *vp_modern_map_vq_notify(struct virtio_pci_modern_device *mdev,
>  }
>  EXPORT_SYMBOL_GPL(vp_modern_map_vq_notify);
>  
> +/*
> + * vp_modern_set_freeze_mode - set freeze mode to device
> + * @mdev: the modern virtio-pci device
> + * @mode: the mode set to device
> + */
> +void vp_modern_set_freeze_mode(struct virtio_pci_modern_device *mdev,
> +				 u16 mode)
> +{
> +	struct virtio_pci_common_cfg __iomem *cfg = mdev->common;
> +
> +	vp_iowrite16(mode, &cfg->freeze_mode);
> +}
> +EXPORT_SYMBOL_GPL(vp_modern_set_freeze_mode);
> +
>  MODULE_VERSION("0.1");
>  MODULE_DESCRIPTION("Modern Virtio PCI Device");
>  MODULE_AUTHOR("Jason Wang <jasowang@redhat.com>");
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index 2b3438de2c4d..2a7443ff7f12 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -120,6 +120,7 @@ struct virtio_config_ops {
>  			       struct virtio_shm_region *region, u8 id);
>  	int (*disable_vq_and_reset)(struct virtqueue *vq);
>  	int (*enable_vq_after_reset)(struct virtqueue *vq);
> +	void (*set_freeze_mode)(struct virtio_device *vdev, u16 mode);
>  };
>  
>  /* If driver didn't advertise the feature, it will never appear. */
> diff --git a/include/linux/virtio_pci_modern.h b/include/linux/virtio_pci_modern.h
> index 067ac1d789bc..ba6eed216ded 100644
> --- a/include/linux/virtio_pci_modern.h
> +++ b/include/linux/virtio_pci_modern.h
> @@ -121,4 +121,6 @@ int vp_modern_probe(struct virtio_pci_modern_device *mdev);
>  void vp_modern_remove(struct virtio_pci_modern_device *mdev);
>  int vp_modern_get_queue_reset(struct virtio_pci_modern_device *mdev, u16 index);
>  void vp_modern_set_queue_reset(struct virtio_pci_modern_device *mdev, u16 index);
> +void vp_modern_set_freeze_mode(struct virtio_pci_modern_device *mdev,
> +		   u16 mode);
>  #endif
> diff --git a/include/uapi/linux/virtio_pci.h b/include/uapi/linux/virtio_pci.h
> index f703afc7ad31..725ace458a1b 100644
> --- a/include/uapi/linux/virtio_pci.h
> +++ b/include/uapi/linux/virtio_pci.h
> @@ -140,6 +140,15 @@ struct virtio_pci_notify_cap {
>  	__le32 notify_off_multiplier;	/* Multiplier for queue_notify_off. */
>  };
>  
> +typedef enum {
> +       VIRTIO_PCI_FREEZE_MODE_UNFREEZE = 0,
> +       VIRTIO_PCI_FREEZE_MODE_FREEZE_S3 = 3,
> +} virtio_pci_freeze_mode_t;

we don't normally do typedefs.

> +
> +#define VIRTIO_PCI_FREEZE_MODE_MASK \
> +	((1 << VIRTIO_PCI_FREEZE_MODE_UNFREEZE) | \
> +	(1 << VIRTIO_PCI_FREEZE_MODE_FREEZE_S3))
> +

not sure why is this useful generally.

>  /* Fields in VIRTIO_PCI_CAP_COMMON_CFG: */
>  struct virtio_pci_common_cfg {
>  	/* About the whole device. */
> @@ -164,6 +173,8 @@ struct virtio_pci_common_cfg {
>  	__le32 queue_avail_hi;		/* read-write */
>  	__le32 queue_used_lo;		/* read-write */
>  	__le32 queue_used_hi;		/* read-write */
> +
> +	__le16 freeze_mode;		/* read-write */
>  };
>

Your patch will likely break uses of sizeof(struct virtio_pci_common_cfg)
on existing devices.
  
>  /* Fields in VIRTIO_PCI_CAP_PCI_CFG: */
> @@ -202,8 +213,9 @@ struct virtio_pci_cfg_cap {
>  #define VIRTIO_PCI_COMMON_Q_AVAILHI	44
>  #define VIRTIO_PCI_COMMON_Q_USEDLO	48
>  #define VIRTIO_PCI_COMMON_Q_USEDHI	52
> -#define VIRTIO_PCI_COMMON_Q_NDATA	56
> -#define VIRTIO_PCI_COMMON_Q_RESET	58
> +#define VIRTIO_PCI_COMMON_F_MODE	56


F_ here stands for freeze? Please don't abbreviate.
Q for queue is a pun that works, F for freeze doesn't.


> +#define VIRTIO_PCI_COMMON_Q_NDATA	58
> +#define VIRTIO_PCI_COMMON_Q_RESET	60
>  
>  #endif /* VIRTIO_PCI_NO_MODERN */
>  
> -- 
> 2.34.1