东莞网站开发建设,网站建设1993seo,广州网站建设有哪些,百度集团总部在哪里接前一篇文章#xff1a;QEMU源码全解析 —— virtio#xff08;21#xff09; 前几回讲解了virtio驱动的加载。本回开始讲解virtio驱动的初始化。
在讲解virtio驱动的初始化之前#xff0c;先要介绍virtio配置的函数集合变量virtio_pci_config_ops。实际上前文书也有提到…接前一篇文章QEMU源码全解析 —— virtio21 前几回讲解了virtio驱动的加载。本回开始讲解virtio驱动的初始化。
在讲解virtio驱动的初始化之前先要介绍virtio配置的函数集合变量virtio_pci_config_ops。实际上前文书也有提到如下图的右上角 virtio_pci_config_ops的初始化有两处分别在Linux内核源码/drivers/virtio/virtio_pci_legacy.c和Linux内核源码/drivers/virtio/virtio_pci_modern.c中。代码分别如下
legacy
static const struct virtio_config_ops virtio_pci_config_ops {.get vp_get,.set vp_set,.get_status vp_get_status,.set_status vp_set_status,.reset vp_reset,.find_vqs vp_find_vqs,.del_vqs vp_del_vqs,.synchronize_cbs vp_synchronize_vectors,.get_features vp_get_features,.finalize_features vp_finalize_features,.bus_name vp_bus_name,.set_vq_affinity vp_set_vq_affinity,.get_vq_affinity vp_get_vq_affinity,
};
modern
static const struct virtio_config_ops virtio_pci_config_ops {.get vp_get,.set vp_set,.generation vp_generation,.get_status vp_get_status,.set_status vp_set_status,.reset vp_reset,.find_vqs vp_modern_find_vqs,.del_vqs vp_del_vqs,.synchronize_cbs vp_synchronize_vectors,.get_features vp_get_features,.finalize_features vp_finalize_features,.bus_name vp_bus_name,.set_vq_affinity vp_set_vq_affinity,.get_vq_affinity vp_get_vq_affinity,.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,
};
在此以Linux内核源码/drivers/virtio/virtio_pci_modern.c中的virtio_pci_config_ops为例进行讲解。
在前文书讲到的virtio_pci_modern_probe函数Linux内核源码/drivers/virtio/virtio_pci_modern.c中
/* the PCI probing function */
int virtio_pci_modern_probe(struct virtio_pci_device *vp_dev)
{struct virtio_pci_modern_device *mdev vp_dev-mdev;struct pci_dev *pci_dev vp_dev-pci_dev;int err;mdev-pci_dev pci_dev;err vp_modern_probe(mdev);if (err)return err;if (mdev-device)vp_dev-vdev.config virtio_pci_config_ops;elsevp_dev-vdev.config virtio_pci_config_nodev_ops;vp_dev-config_vector vp_config_vector;vp_dev-setup_vq setup_vq;vp_dev-del_vq del_vq;vp_dev-isr mdev-isr;vp_dev-vdev.id mdev-id;return 0;
}
virtio_pci_config_ops变量被赋值给了virtio_device结构的config成员。struct virtio_device的定义在Linux内核源码/include/linux/virtio.h中代码如下
/*** struct virtio_device - representation of a device using virtio* index: unique position on the virtio bus* failed: saved value for VIRTIO_CONFIG_S_FAILED bit (for restore)* config_enabled: configuration change reporting enabled* config_change_pending: configuration change reported while disabled* config_lock: protects configuration change reporting* vqs_list_lock: protects vqs.* dev: underlying device.* id: the device type identification (used to match it with a driver).* config: the configuration ops for this device.* vringh_config: configuration ops for host vrings.* vqs: the list of virtqueues for this device.* features: the features supported by both driver and device.* priv: private pointer for the drivers use.*/
struct virtio_device {int index;bool failed;bool config_enabled;bool config_change_pending;spinlock_t config_lock;spinlock_t vqs_list_lock;struct device dev;struct virtio_device_id id;const struct virtio_config_ops *config;const struct vringh_config_ops *vringh_config;struct list_head vqs;u64 features;void *priv;
};
其中的struct virtio_config_ops的定义在Linux内核源码/include/linux/virtio_config.h中代码如下
/*** struct virtio_config_ops - operations for configuring a virtio device* Note: Do not assume that a transport implements all of the operations* getting/setting a value as a simple read/write! Generally speaking,* any of get/set, get_status/set_status, or get_features/* finalize_features are NOT safe to be called from an atomic* context.* get: read the value of a configuration field* vdev: the virtio_device* offset: the offset of the configuration field* buf: the buffer to write the field value into.* len: the length of the buffer* set: write the value of a configuration field* vdev: the virtio_device* offset: the offset of the configuration field* buf: the buffer to read the field value from.* len: the length of the buffer* generation: config generation counter (optional)* vdev: the virtio_device* Returns the config generation counter* get_status: read the status byte* vdev: the virtio_device* Returns the status byte* set_status: write the status byte* vdev: the virtio_device* status: the new status byte* reset: reset the device* vdev: the virtio device* After this, status and feature negotiation must be done again* Device must not be reset from its vq/config callbacks, or in* parallel with being added/removed.* find_vqs: find virtqueues and instantiate them.* vdev: the virtio_device* nvqs: the number of virtqueues to find* vqs: on success, includes new virtqueues* callbacks: array of callbacks, for each virtqueue* include a NULL entry for vqs that do not need a callback* names: array of virtqueue names (mainly for debugging)* include a NULL entry for vqs unused by driver* Returns 0 on success or error status* del_vqs: free virtqueues found by find_vqs().* synchronize_cbs: synchronize with the virtqueue callbacks (optional)* The function guarantees that all memory operations on the* queue before it are visible to the vring_interrupt() that is* called after it.* vdev: the virtio_device* get_features: get the array of feature bits for this device.* vdev: the virtio_device* Returns the first 64 feature bits (all we currently need).* finalize_features: confirm what device features well be using.* vdev: the virtio_device* This sends the driver feature bits to the device: it can change* the dev-feature bits if it wants.* Note that despite the name this can be called any number of* times.* Returns 0 on success or error status* bus_name: return the bus name associated with the device (optional)* vdev: the virtio_device* This returns a pointer to the bus name a la pci_name from which* the caller can then copy.* set_vq_affinity: set the affinity for a virtqueue (optional).* get_vq_affinity: get the affinity for a virtqueue (optional).* get_shm_region: get a shared memory region based on the index.* disable_vq_and_reset: reset a queue individually (optional).* vq: the virtqueue* Returns 0 on success or error status* disable_vq_and_reset will guarantee that the callbacks are disabled and* synchronized.* Except for the callback, the caller should guarantee that the vring is* not accessed by any functions of virtqueue.* enable_vq_after_reset: enable a reset queue* vq: the virtqueue* Returns 0 on success or error status* If disable_vq_and_reset is set, then enable_vq_after_reset must also be* set.*/
struct virtio_config_ops {void (*get)(struct virtio_device *vdev, unsigned offset,void *buf, unsigned len);void (*set)(struct virtio_device *vdev, unsigned offset,const void *buf, unsigned len);u32 (*generation)(struct virtio_device *vdev);u8 (*get_status)(struct virtio_device *vdev);void (*set_status)(struct virtio_device *vdev, u8 status);void (*reset)(struct virtio_device *vdev);int (*find_vqs)(struct virtio_device *, unsigned nvqs,struct virtqueue *vqs[], vq_callback_t *callbacks[],const char * const names[], const bool *ctx,struct irq_affinity *desc);void (*del_vqs)(struct virtio_device *);void (*synchronize_cbs)(struct virtio_device *);u64 (*get_features)(struct virtio_device *vdev);int (*finalize_features)(struct virtio_device *vdev);const char *(*bus_name)(struct virtio_device *vdev);int (*set_vq_affinity)(struct virtqueue *vq,const struct cpumask *cpu_mask);const struct cpumask *(*get_vq_affinity)(struct virtio_device *vdev,int index);bool (*get_shm_region)(struct virtio_device *vdev,struct virtio_shm_region *region, u8 id);int (*disable_vq_and_reset)(struct virtqueue *vq);int (*enable_vq_after_reset)(struct virtqueue *vq);
};
再回过头来看一下Linux内核源码/drivers/virtio/virtio_pci_modern.c中的virtio_pci_config_ops对照着上边 struct virtio_config_ops的定义。
static const struct virtio_config_ops virtio_pci_config_ops {.get vp_get,.set vp_set,.generation vp_generation,.get_status vp_get_status,.set_status vp_set_status,.reset vp_reset,.find_vqs vp_modern_find_vqs,.del_vqs vp_del_vqs,.synchronize_cbs vp_synchronize_vectors,.get_features vp_get_features,.finalize_features vp_finalize_features,.bus_name vp_bus_name,.set_vq_affinity vp_set_vq_affinity,.get_vq_affinity vp_get_vq_affinity,.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,
};
virtio_pci_config_ops结构中的成员函数通常是virtio PCI代理设备的IO操作包括读写virtio PCI代理设备的PIO和MMIO如get_status和set_status成员对应的vp_get_status函数和vp_set_status函数。分别来看
get_status
根据struct virtio_config_ops中的说明 get_status: read the status byte * vdev: the virtio_device * Returns the status byte get_status的作用是读取状态字节。有一个参数vdev代表了virtio device。返回值为读取到的状态字节。
get_status所指向的vp_get_status函数也在Linux内核源码/drivers/virtio/virtio_pci_modern.c中代码如下
/* config-{get,set}_status() implementations */
static u8 vp_get_status(struct virtio_device *vdev)
{struct virtio_pci_device *vp_dev to_vp_device(vdev);return vp_modern_get_status(vp_dev-mdev);
}
vp_modern_get_status函数在Linux内核源码/drivers/virtio/virtio_pci_modern_dev.c中代码如下
/** vp_modern_get_status - get the device status* mdev: the modern virtio-pci device** Returns the status read from device*/
u8 vp_modern_get_status(struct virtio_pci_modern_device *mdev)
{struct virtio_pci_common_cfg __iomem *cfg mdev-common;return vp_ioread8(cfg-device_status);
}
EXPORT_SYMBOL_GPL(vp_modern_get_status);
set_status set_status: write the status byte * vdev: the virtio_device * status: the new status byte set_status的作用是写入状态字节。有两个参数vdev代表了virtio devicestatus为新的要写入的状态字节。
set_status所指向的vp_set_status函数也在Linux内核源码/drivers/virtio/virtio_pci_modern.c中代码如下
static void vp_set_status(struct virtio_device *vdev, u8 status)
{struct virtio_pci_device *vp_dev to_vp_device(vdev);/* We should never be setting status to 0. */BUG_ON(status 0);vp_modern_set_status(vp_dev-mdev, status);
}
vp_modern_set_status函数在Linux内核源码/drivers/virtio/virtio_pci_modern_dev.c中代码如下
/** vp_modern_set_status - set status to device* mdev: the modern virtio-pci device* status: the status set to device*/
void vp_modern_set_status(struct virtio_pci_modern_device *mdev,u8 status)
{struct virtio_pci_common_cfg __iomem *cfg mdev-common;/** Per memory-barriers.txt, wmb() is not needed to guarantee* that the cache coherent memory writes have completed* before writing to the MMIO region.*/vp_iowrite8(status, cfg-device_status);
}
EXPORT_SYMBOL_GPL(vp_modern_set_status);
vp_modern_get_status和vp_modern_set_status函数直接读写vp_dev-mdev-common-device_status。从前文书QEMU源码全解析 —— virtio14的讲解可知vp_dev-common对应的是virtio PCI代理设备第四个BAR表示的地址中的一段空间。 vp_dev-mdev-common的类型为struct virtio_pci_common_cfg该结构的定义在Linux内核源码/include/uapi/linux/virtio_pci.h中代码如下
/* Fields in VIRTIO_PCI_CAP_COMMON_CFG: */
struct virtio_pci_common_cfg {/* About the whole device. */__le32 device_feature_select; /* read-write */__le32 device_feature; /* read-only */__le32 guest_feature_select; /* read-write */__le32 guest_feature; /* read-write */__le16 msix_config; /* read-write */__le16 num_queues; /* read-only */__u8 device_status; /* read-write */__u8 config_generation; /* read-only *//* About a specific virtqueue. */__le16 queue_select; /* read-write */__le16 queue_size; /* read-write, power of 2. */__le16 queue_msix_vector; /* read-write */__le16 queue_enable; /* read-write */__le16 queue_notify_off; /* read-only */__le32 queue_desc_lo; /* read-write */__le32 queue_desc_hi; /* read-write */__le32 queue_avail_lo; /* read-write */__le32 queue_avail_hi; /* read-write */__le32 queue_used_lo; /* read-write */__le32 queue_used_hi; /* read-write */
};
struct virtio_pci_common_cfg的每一个成员都表示一个virtio PCI代理设备modern MMIO地址空间中对应的值读写这写成员都会陷入到QEMU中。比如上面的读取或者设置设备状态的device_status成员其地址从virtio_pci_common_cfg结构开始的偏移20字节处44442220所以读写该地址的时候会陷入到QEMU中并且地址是virtio设备的common MemoryRegion偏移20字节处。该MemoryRegion对应的回调操作结构是common_ops类型为MemoryRegionOps。
common_ops在hw/virtio/virtio-pci.c中初始化代码如下
static void virtio_pci_modern_regions_init(VirtIOPCIProxy *proxy,const char *vdev_name)
{static const MemoryRegionOps common_ops {.read virtio_pci_common_read,.write virtio_pci_common_write,.impl {.min_access_size 1,.max_access_size 4,},.endianness DEVICE_LITTLE_ENDIAN,};……
}
回到struct_pci_config_ops。
static const struct virtio_config_ops virtio_pci_config_ops {.get vp_get,.set vp_set,.generation vp_generation,.get_status vp_get_status,.set_status vp_set_status,.reset vp_reset,.find_vqs vp_modern_find_vqs,.del_vqs vp_del_vqs,.synchronize_cbs vp_synchronize_vectors,.get_features vp_get_features,.finalize_features vp_finalize_features,.bus_name vp_bus_name,.set_vq_affinity vp_set_vq_affinity,.get_vq_affinity vp_get_vq_affinity,.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,
};
virtio_pci_config_ops的各个函数封装了这些I/O操作不仅是MMO操作还有PIO操作。virtio设备可以通过此结构中的各个回调函数来驱动设备。
本回就讲到这里。下一回以virtio balloon设备的初始化过程为例分析virtio设备的初始化过程即上一回讲到的virtio驱动初始化设备的过程中的“执行设备相关的初始化操作”一步。
欲知后事如何且看下回分解。
