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

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Message-ID: <6608853f-7426-7b79-da1a-29c8fcc6ffc3@nvidia.com>
Date:   Sun, 17 Oct 2021 17:03:28 +0300
From:   Yishai Hadas <yishaih@...dia.com>
To:     Alex Williamson <alex.williamson@...hat.com>,
        Jason Gunthorpe <jgg@...dia.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 10/15/2021 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))
            return -EINVAL;

As was suggested to have some new const for ERROR STATE and use it in 
drivers when state gets into error I may come in V2 with the below extra 
patch.

Any comments on ?

commit cc7cb23773c70b998aaee5bfc2434da86c80b600
Author: Yishai Hadas <yishaih@...dia.com>
Date:   Sun Oct 17 11:34:06 2021 +0300

     Vfio: Add a const value for VFIO_DEVICE_STATE_ERROR

     Add a const value for VFIO_DEVICE_STATE_ERROR to be used by drivers to
     set an error state.

     Signed-off-by: Yishai Hadas <yishaih@...dia.com>

diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index b53a9557884a..37376dadca5a 100644
--- a/include/linux/vfio.h
+++ 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;


Yishai