linux-kernel - 答复: [PATCH v1 01/14] vfio: Create vfio_fs

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Date:   Fri, 9 Apr 2021 04:54:23 +0000
From:   "Zengtao (B)" <prime.zeng@...ilicon.com>
To:     Alex Williamson <alex.williamson@...hat.com>
CC:     "cohuck@...hat.com" <cohuck@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jgg@...dia.com" <jgg@...dia.com>,
        "peterx@...hat.com" <peterx@...hat.com>
Subject: 答复: [PATCH v1 01/14] vfio: Create vfio_fs_type with inode per device

> -----邮件原件-----
> 发件人: Alex Williamson [mailto:alex.williamson@...hat.com]
> 发送时间: 2021年3月9日 5:47
> 收件人: alex.williamson@...hat.com
> 抄送: cohuck@...hat.com; kvm@...r.kernel.org;
> linux-kernel@...r.kernel.org; jgg@...dia.com; peterx@...hat.com
> 主题: [PATCH v1 01/14] vfio: Create vfio_fs_type with inode per device
> 
> By linking all the device fds we provide to userspace to an address space
> through a new pseudo fs, we can use tools like
> unmap_mapping_range() to zap all vmas associated with a device.
> 
> Suggested-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> ---
>  drivers/vfio/vfio.c |   54
> +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 54 insertions(+)
> 
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index
> 38779e6fd80c..abdf8d52a911 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -32,11 +32,18 @@
>  #include <linux/vfio.h>
>  #include <linux/wait.h>
>  #include <linux/sched/signal.h>
> +#include <linux/pseudo_fs.h>
> +#include <linux/mount.h>
Minor: keep the headers in alphabetical order.

> 
>  #define DRIVER_VERSION	"0.3"
>  #define DRIVER_AUTHOR	"Alex Williamson <alex.williamson@...hat.com>"
>  #define DRIVER_DESC	"VFIO - User Level meta-driver"
> 
> +#define VFIO_MAGIC 0x5646494f /* "VFIO" */
Move to include/uapi/linux/magic.h ? 

> +
> +static int vfio_fs_cnt;
> +static struct vfsmount *vfio_fs_mnt;
> +
>  static struct vfio {
>  	struct class			*class;
>  	struct list_head		iommu_drivers_list;
> @@ -97,6 +104,7 @@ struct vfio_device {
>  	struct vfio_group		*group;
>  	struct list_head		group_next;
>  	void				*device_data;
> +	struct inode			*inode;
>  };
> 
>  #ifdef CONFIG_VFIO_NOIOMMU
> @@ -529,6 +537,34 @@ static struct vfio_group
> *vfio_group_get_from_dev(struct device *dev)
>  	return group;
>  }
> 
> +static int vfio_fs_init_fs_context(struct fs_context *fc) {
> +	return init_pseudo(fc, VFIO_MAGIC) ? 0 : -ENOMEM; }
> +
> +static struct file_system_type vfio_fs_type = {
> +	.name = "vfio",
> +	.owner = THIS_MODULE,
> +	.init_fs_context = vfio_fs_init_fs_context,
> +	.kill_sb = kill_anon_super,
> +};
> +
> +static struct inode *vfio_fs_inode_new(void) {
> +	struct inode *inode;
> +	int ret;
> +
> +	ret = simple_pin_fs(&vfio_fs_type, &vfio_fs_mnt, &vfio_fs_cnt);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	inode = alloc_anon_inode(vfio_fs_mnt->mnt_sb);
> +	if (IS_ERR(inode))
> +		simple_release_fs(&vfio_fs_mnt, &vfio_fs_cnt);
> +
> +	return inode;
> +}
> +
>  /**
>   * Device objects - create, release, get, put, search
>   */
> @@ -539,11 +575,19 @@ struct vfio_device
> *vfio_group_create_device(struct vfio_group *group,
>  					     void *device_data)
>  {
>  	struct vfio_device *device;
> +	struct inode *inode;
> 
>  	device = kzalloc(sizeof(*device), GFP_KERNEL);
>  	if (!device)
>  		return ERR_PTR(-ENOMEM);
> 
> +	inode = vfio_fs_inode_new();
> +	if (IS_ERR(inode)) {
> +		kfree(device);
> +		return ERR_CAST(inode);
> +	}
> +	device->inode = inode;
> +
>  	kref_init(&device->kref);
>  	device->dev = dev;
>  	device->group = group;
> @@ -574,6 +618,9 @@ static void vfio_device_release(struct kref *kref)
> 
>  	dev_set_drvdata(device->dev, NULL);
> 
> +	iput(device->inode);
> +	simple_release_fs(&vfio_fs_mnt, &vfio_fs_cnt);
> +
>  	kfree(device);
> 
>  	/* vfio_del_group_dev may be waiting for this device */ @@ -1488,6
> +1535,13 @@ static int vfio_group_get_device_fd(struct vfio_group *group,
> char *buf)
>  	 */
>  	filep->f_mode |= (FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
> 
> +	/*
> +	 * Use the pseudo fs inode on the device to link all mmaps
> +	 * to the same address space, allowing us to unmap all vmas
> +	 * associated to this device using unmap_mapping_range().
> +	 */
> +	filep->f_mapping = device->inode->i_mapping;
> +
>  	atomic_inc(&group->container_users);
> 
>  	fd_install(ret, filep);