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

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Date:   Mon, 18 Oct 2021 16:46:35 +0300
From:   Yishai Hadas <yishaih@...dia.com>
To:     Alex Williamson <alex.williamson@...hat.com>
CC:     Jason Gunthorpe <jgg@...dia.com>, <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 4:42 PM, Alex Williamson wrote:
> On Mon, 18 Oct 2021 16:26:16 +0300
> Yishai Hadas <yishaih@...dia.com> wrote:
>
>> 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 ?
> I don't understand why this wouldn't just be a continuation of the
> #defines in the uapi header.  Thanks,
>
> Alex
>

Sure, let's go with this.

Thanks,
Yishai