netdev - Re: [PATCH V1 mlx5-next 11/13] vfio/mlx5: Implement vfio

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Message-ID: <c27a775f-f003-b652-ea80-f6ea988c0e78@nvidia.com>
Date:   Mon, 18 Oct 2021 16:26:16 +0300
From:   Yishai Hadas <yishaih@...dia.com>
To:     Jason Gunthorpe <jgg@...dia.com>,
        Alex Williamson <alex.williamson@...hat.com>
CC:     <bhelgaas@...gle.com>, <saeedm@...dia.com>,
        <linux-pci@...r.kernel.org>, <kvm@...r.kernel.org>,
        <netdev@...r.kernel.org>, <kuba@...nel.org>, <leonro@...dia.com>,
        <kwankhede@...dia.com>, <mgurtovoy@...dia.com>, <maorg@...dia.com>
Subject: Re: [PATCH V1 mlx5-next 11/13] vfio/mlx5: Implement vfio_pci driver
 for mlx5 devices

On 10/18/2021 2:51 PM, Jason Gunthorpe wrote:
> On Sun, Oct 17, 2021 at 05:03:28PM +0300, Yishai Hadas wrote:
>> On 10/15/2021 11:59 PM, Alex Williamson wrote:
>>> On Fri, 15 Oct 2021 17:16:54 -0300
>>> Jason Gunthorpe <jgg@...dia.com> wrote:
>>>
>>>> On Fri, Oct 15, 2021 at 02:12:01PM -0600, Alex Williamson wrote:
>>>>> On Fri, 15 Oct 2021 16:59:37 -0300
>>>>> Jason Gunthorpe <jgg@...dia.com> wrote:
>>>>>> On Fri, Oct 15, 2021 at 01:48:20PM -0600, Alex Williamson wrote:
>>>>>>>> +static int mlx5vf_pci_set_device_state(struct mlx5vf_pci_core_device *mvdev,
>>>>>>>> +				       u32 state)
>>>>>>>> +{
>>>>>>>> +	struct mlx5vf_pci_migration_info *vmig = &mvdev->vmig;
>>>>>>>> +	u32 old_state = vmig->vfio_dev_state;
>>>>>>>> +	int ret = 0;
>>>>>>>> +
>>>>>>>> +	if (vfio_is_state_invalid(state) || vfio_is_state_invalid(old_state))
>>>>>>>> +		return -EINVAL;
>>>>>>> if (!VFIO_DEVICE_STATE_VALID(old_state) || !VFIO_DEVICE_STATE_VALID(state))
>>>>>> AFAICT this macro doesn't do what is needed, eg
>>>>>>
>>>>>> VFIO_DEVICE_STATE_VALID(0xF000) == true
>>>>>>
>>>>>> What Yishai implemented is at least functionally correct - states this
>>>>>> driver does not support are rejected.
>>>>> if (!VFIO_DEVICE_STATE_VALID(old_state) || !VFIO_DEVICE_STATE_VALID(state)) || (state & ~VFIO_DEVICE_STATE_MASK))
>>>>>
>>>>> old_state is controlled by the driver and can never have random bits
>>>>> set, user state should be sanitized to prevent setting undefined bits.
>>>> In that instance let's just write
>>>>
>>>> old_state != VFIO_DEVICE_STATE_ERROR
>>>>
>>>> ?
>>> Not quite, the user can't set either of the other invalid states
>>> either.
>>
>> OK so let's go with below as you suggested.
>> if (!VFIO_DEVICE_STATE_VALID(old_state) ||
>>       !VFIO_DEVICE_STATE_VALID(state) ||
>>        (state & ~VFIO_DEVICE_STATE_MASK))
>>             
> This is my preference:
>
> if (vmig->vfio_dev_state != VFIO_DEVICE_STATE_ERROR ||
>      !vfio_device_state_valid(state) ||
>      (state & !MLX5VF_SUPPORTED_DEVICE_STATES))
>

OK, let's go with this approach which enforces what the driver supports 
as well.

We may have the below post making it accurate and complete.

enum {
     MLX5VF_SUPPORTED_DEVICE_STATES = VFIO_DEVICE_STATE_RUNNING |
                                      VFIO_DEVICE_STATE_SAVING |
                                      VFIO_DEVICE_STATE_RESUMING,
};

if (old_state == VFIO_DEVICE_STATE_ERROR ||
     !vfio_device_state_valid(state) ||
     (state & ~MLX5VF_SUPPORTED_DEVICE_STATES))
           return -EINVAL;

>> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
>> index b53a9557884a..37376dadca5a 100644
>> +++ b/include/linux/vfio.h
>> @@ -15,6 +15,8 @@
>>   #include <linux/poll.h>
>>   #include <uapi/linux/vfio.h>
>>
>> +static const int VFIO_DEVICE_STATE_ERROR = VFIO_DEVICE_STATE_SAVING |
>> + VFIO_DEVICE_STATE_RESUMING;
> Do not put static variables in header files
>
> Jason

OK, we can come with an enum instead.

enum {

VFIO_DEVICE_STATE_ERROR = VFIO_DEVICE_STATE_SAVING | VFIO_DEVICE_STATE_RESUMING,

};

Alex,

Do you prefer to  put it under include/uapi/vfio.h or that it can go 
under inlcude/linux/vfio.h for internal drivers usage ?

Yishai