Re: [PATCH v1 05/22] vfio/common: Extract out vfio_kvm_device_[add/del]_fd

["Cédric Le Goater" <clg@redhat.com>]

On 9/20/23 13:49, Eric Auger wrote:
> Hi Zhenzhong,
> 
> On 8/30/23 12:37, Zhenzhong Duan wrote:
>> ...which will be used by both legacy and iommufd backend.
> I prefer genuine sentences in the commit msg. Also you explain what you
> do but not why.
> 
> suggestion: Introduce two new helpers, vfio_kvm_device_[add/del]_fd
> which take as input a file descriptor which can be either a group fd or
> a cdev fd. This uses the new KVM_DEV_VFIO_FILE VFIO KVM device group,
> which aliases to the legacy KVM_DEV_VFIO_GROUP.

Ah yes. I didn't understand why the 's/GROUP/FILE/' change in the
VFIO KVM device ioctls. Thanks for clarifying.

What about pre-6.6 kernels without KVM_DEV_VFIO_FILE support ?

C.


> 
> vfio_kvm_device_add/del_group then call those new helpers.
> 
> 
> 
>>
>> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>> ---
>>   hw/vfio/common.c              | 44 +++++++++++++++++++++++------------
>>   include/hw/vfio/vfio-common.h |  3 +++
>>   2 files changed, 32 insertions(+), 15 deletions(-)
>>
>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
>> index 67150e4575..949ad6714a 100644
>> --- a/hw/vfio/common.c
>> +++ b/hw/vfio/common.c
>> @@ -1759,17 +1759,17 @@ void vfio_reset_handler(void *opaque)
>>       }
>>   }
>>   
>> -static void vfio_kvm_device_add_group(VFIOGroup *group)
>> +int vfio_kvm_device_add_fd(int fd)
>>   {
>>   #ifdef CONFIG_KVM
>>       struct kvm_device_attr attr = {
>> -        .group = KVM_DEV_VFIO_GROUP,
>> -        .attr = KVM_DEV_VFIO_GROUP_ADD,
>> -        .addr = (uint64_t)(unsigned long)&group->fd,
>> +        .group = KVM_DEV_VFIO_FILE,
>> +        .attr = KVM_DEV_VFIO_FILE_ADD,
>> +        .addr = (uint64_t)(unsigned long)&fd,
>>       };
>>   
>>       if (!kvm_enabled()) {
>> -        return;
>> +        return 0;
>>       }
>>   
>>       if (vfio_kvm_device_fd < 0) {
>> @@ -1779,37 +1779,51 @@ static void vfio_kvm_device_add_group(VFIOGroup *group)
>>   
>>           if (kvm_vm_ioctl(kvm_state, KVM_CREATE_DEVICE, &cd)) {
>>               error_report("Failed to create KVM VFIO device: %m");
>> -            return;
>> +            return -ENODEV;
> can't you return -errno?
>>           }
>>   
>>           vfio_kvm_device_fd = cd.fd;
>>       }
>>   
>>       if (ioctl(vfio_kvm_device_fd, KVM_SET_DEVICE_ATTR, &attr)) {
>> -        error_report("Failed to add group %d to KVM VFIO device: %m",
>> -                     group->groupid);
>> +        error_report("Failed to add fd %d to KVM VFIO device: %m",
>> +                     fd);
>> +        return -errno;
>>       }
>>   #endif
>> +    return 0;
>>   }
>>   
>> -static void vfio_kvm_device_del_group(VFIOGroup *group)
>> +static void vfio_kvm_device_add_group(VFIOGroup *group)
>> +{
>> +    vfio_kvm_device_add_fd(group->fd);
> Since vfio_kvm_device_add_fd now returns an error value, it's a pity not
> to use it and propagate it. Also you could fill an errp with the error
> msg and use it in vfio_connect_container(). But this is a new error
> handling there.
>> +}
>> +
>> +int vfio_kvm_device_del_fd(int fd)
> not sure we want this to return an error. But if we do, I think it would
> be nicer to propagate the error up.
>>   {
>>   #ifdef CONFIG_KVM
>>       struct kvm_device_attr attr = {
>> -        .group = KVM_DEV_VFIO_GROUP,
>> -        .attr = KVM_DEV_VFIO_GROUP_DEL,
>> -        .addr = (uint64_t)(unsigned long)&group->fd,
>> +        .group = KVM_DEV_VFIO_FILE,
>> +        .attr = KVM_DEV_VFIO_FILE_DEL,
>> +        .addr = (uint64_t)(unsigned long)&fd,
>>       };
>>   
>>       if (vfio_kvm_device_fd < 0) {
>> -        return;
>> +        return -EINVAL;
>>       }
>>   
>>       if (ioctl(vfio_kvm_device_fd, KVM_SET_DEVICE_ATTR, &attr)) {
>> -        error_report("Failed to remove group %d from KVM VFIO device: %m",
>> -                     group->groupid);
>> +        error_report("Failed to remove fd %d from KVM VFIO device: %m",
>> +                     fd);
>> +        return -EBADF;
> -errno?
>>       }
>>   #endif
>> +    return 0;
>> +}
>> +
>> +static void vfio_kvm_device_del_group(VFIOGroup *group)
>> +{
>> +    vfio_kvm_device_del_fd(group->fd);
>>   }
>>   
>>   static VFIOAddressSpace *vfio_get_address_space(AddressSpace *as)
>> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
>> index 5e376c436e..598c3ce079 100644
>> --- a/include/hw/vfio/vfio-common.h
>> +++ b/include/hw/vfio/vfio-common.h
>> @@ -220,6 +220,9 @@ struct vfio_device_info *vfio_get_device_info(int fd);
>>   int vfio_get_device(VFIOGroup *group, const char *name,
>>                       VFIODevice *vbasedev, Error **errp);
>>   
>> +int vfio_kvm_device_add_fd(int fd);
>> +int vfio_kvm_device_del_fd(int fd);
>> +
>>   extern const MemoryRegionOps vfio_region_ops;
>>   typedef QLIST_HEAD(VFIOGroupList, VFIOGroup) VFIOGroupList;
>>   extern VFIOGroupList vfio_group_list;
> Thanks
> 
> Eric
>