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

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Date:   Mon, 18 Oct 2021 07:42:32 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Yishai Hadas <yishaih@...dia.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 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