Re: [PATCH v10 05/22] kvm/vfio: Accept vfio device file from userspace

["Cédric Le Goater" <clegoate@redhat.com>]

On 4/26/23 17:03, Yi Liu wrote:
> This defines KVM_DEV_VFIO_FILE* and make alias with KVM_DEV_VFIO_GROUP*.
> Old userspace uses KVM_DEV_VFIO_GROUP* works as well.
> 
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> Tested-by: Terrence Xu <terrence.xu@intel.com>
> Tested-by: Nicolin Chen <nicolinc@nvidia.com>
> Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
> Tested-by: Yanting Jiang <yanting.jiang@intel.com>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> ---
>   Documentation/virt/kvm/devices/vfio.rst | 47 ++++++++++++++++---------
>   include/uapi/linux/kvm.h                | 13 +++++--
>   virt/kvm/vfio.c                         | 16 ++++-----
>   3 files changed, 49 insertions(+), 27 deletions(-)
> 
> diff --git a/Documentation/virt/kvm/devices/vfio.rst b/Documentation/virt/kvm/devices/vfio.rst
> index 08b544212638..c549143bb891 100644
> --- a/Documentation/virt/kvm/devices/vfio.rst
> +++ b/Documentation/virt/kvm/devices/vfio.rst
> @@ -9,22 +9,34 @@ Device types supported:
>     - KVM_DEV_TYPE_VFIO
>   
>   Only one VFIO instance may be created per VM.  The created device
> -tracks VFIO groups in use by the VM and features of those groups
> -important to the correctness and acceleration of the VM.  As groups
> -are enabled and disabled for use by the VM, KVM should be updated
> -about their presence.  When registered with KVM, a reference to the
> -VFIO-group is held by KVM.
> +tracks VFIO files (group or device) in use by the VM and features
> +of those groups/devices important to the correctness and acceleration
> +of the VM.  As groups/devices are enabled and disabled for use by the
> +VM, KVM should be updated about their presence.  When registered with
> +KVM, a reference to the VFIO file is held by KVM.
>   
>   Groups:
> -  KVM_DEV_VFIO_GROUP
> -
> -KVM_DEV_VFIO_GROUP attributes:
> -  KVM_DEV_VFIO_GROUP_ADD: Add a VFIO group to VFIO-KVM device tracking
> -	kvm_device_attr.addr points to an int32_t file descriptor
> -	for the VFIO group.
> -  KVM_DEV_VFIO_GROUP_DEL: Remove a VFIO group from VFIO-KVM device tracking
> -	kvm_device_attr.addr points to an int32_t file descriptor
> -	for the VFIO group.
> +  KVM_DEV_VFIO_FILE
> +	alias: KVM_DEV_VFIO_GROUP
> +
> +KVM_DEV_VFIO_FILE attributes:
> +  KVM_DEV_VFIO_FILE_ADD: Add a VFIO file (group/device) to VFIO-KVM device
> +	tracking
> +
> +	kvm_device_attr.addr points to an int32_t file descriptor for the
> +	VFIO file.
> +
> +  KVM_DEV_VFIO_FILE_DEL: Remove a VFIO file (group/device) from VFIO-KVM
> +	device tracking
> +
> +	kvm_device_attr.addr points to an int32_t file descriptor for the
> +	VFIO file.
> +
> +KVM_DEV_VFIO_GROUP (legacy kvm device group restricted to the handling of VFIO group fd):
> +  KVM_DEV_VFIO_GROUP_ADD: same as KVM_DEV_VFIO_FILE_ADD for group fd only
> +
> +  KVM_DEV_VFIO_GROUP_DEL: same as KVM_DEV_VFIO_FILE_DEL for group fd only
> +
>     KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE: attaches a guest visible TCE table
>   	allocated by sPAPR KVM.
>   	kvm_device_attr.addr points to a struct::
> @@ -40,7 +52,10 @@ KVM_DEV_VFIO_GROUP attributes:
>   	- @tablefd is a file descriptor for a TCE table allocated via
>   	  KVM_CREATE_SPAPR_TCE.
>   
> -The GROUP_ADD operation above should be invoked prior to accessing the
> +The FILE/GROUP_ADD operation above should be invoked prior to accessing the
>   device file descriptor via VFIO_GROUP_GET_DEVICE_FD in order to support
>   drivers which require a kvm pointer to be set in their .open_device()
> -callback.
> +callback.  It is the same for device file descriptor via character device
> +open which gets device access via VFIO_DEVICE_BIND_IOMMUFD.  For such file
> +descriptors, FILE_ADD should be invoked before VFIO_DEVICE_BIND_IOMMUFD
> +to support the drivers mentioned in prior sentence as well.
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index d77aef872a0a..7980c7533136 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1410,9 +1410,16 @@ struct kvm_device_attr {
>   	__u64	addr;		/* userspace address of attr data */
>   };
>   
> -#define  KVM_DEV_VFIO_GROUP			1
> -#define   KVM_DEV_VFIO_GROUP_ADD			1
> -#define   KVM_DEV_VFIO_GROUP_DEL			2
> +#define  KVM_DEV_VFIO_FILE			1
> +
> +#define   KVM_DEV_VFIO_FILE_ADD			1
> +#define   KVM_DEV_VFIO_FILE_DEL			2
> +
> +/* KVM_DEV_VFIO_GROUP aliases are for compile time uapi compatibility */
> +#define  KVM_DEV_VFIO_GROUP	KVM_DEV_VFIO_FILE
> +
> +#define   KVM_DEV_VFIO_GROUP_ADD	KVM_DEV_VFIO_FILE_ADD
> +#define   KVM_DEV_VFIO_GROUP_DEL	KVM_DEV_VFIO_FILE_DEL
>   #define   KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE		3
>   
>   enum kvm_device_type {
> diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
> index 8f7fa07e8170..10a3c7ccadf1 100644
> --- a/virt/kvm/vfio.c
> +++ b/virt/kvm/vfio.c
> @@ -286,18 +286,18 @@ static int kvm_vfio_set_file(struct kvm_device *dev, long attr,
>   	int32_t fd;
>   
>   	switch (attr) {
> -	case KVM_DEV_VFIO_GROUP_ADD:
> +	case KVM_DEV_VFIO_FILE_ADD:
>   		if (get_user(fd, argp))
>   			return -EFAULT;
>   		return kvm_vfio_file_add(dev, fd);
>   
> -	case KVM_DEV_VFIO_GROUP_DEL:
> +	case KVM_DEV_VFIO_FILE_DEL:
>   		if (get_user(fd, argp))
>   			return -EFAULT;
>   		return kvm_vfio_file_del(dev, fd);
>   
>   #ifdef CONFIG_SPAPR_TCE_IOMMU
> -	case KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE:
> +	case KVM_DEV_VFIO_FILE_SET_SPAPR_TCE:

This should still be DEV_VFIO_GROUP_SET_SPAPR_TCE. Same below.

>   		return kvm_vfio_file_set_spapr_tce(dev, arg);
>   #endif
>   	}
> @@ -309,7 +309,7 @@ static int kvm_vfio_set_attr(struct kvm_device *dev,
>   			     struct kvm_device_attr *attr)
>   {
>   	switch (attr->group) {
> -	case KVM_DEV_VFIO_GROUP:
> +	case KVM_DEV_VFIO_FILE:
>   		return kvm_vfio_set_file(dev, attr->attr,
>   					 u64_to_user_ptr(attr->addr));
>   	}
> @@ -321,12 +321,12 @@ static int kvm_vfio_has_attr(struct kvm_device *dev,
>   			     struct kvm_device_attr *attr)
>   {
>   	switch (attr->group) {
> -	case KVM_DEV_VFIO_GROUP:
> +	case KVM_DEV_VFIO_FILE:
>   		switch (attr->attr) {
> -		case KVM_DEV_VFIO_GROUP_ADD:
> -		case KVM_DEV_VFIO_GROUP_DEL:
> +		case KVM_DEV_VFIO_FILE_ADD:
> +		case KVM_DEV_VFIO_FILE_DEL:
>   #ifdef CONFIG_SPAPR_TCE_IOMMU
> -		case KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE:
> +		case KVM_DEV_VFIO_FILE_SET_SPAPR_TCE:

Probably an error due to a global rename change.

Thanks,

C.

>   #endif
>   			return 0;
>   		}