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

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Date:   Fri, 15 Oct 2021 14:59:21 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Yishai Hadas <yishaih@...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 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.

> 
> I'm happy to see some device specific mask selecting the bits it
> supports.

There are currently no optional bits within the mask, but the
RESUME|RUNNING state is rather TBD.  I figured we'd use flags in the
region info to advertise additional feature bits when it comes to that.
Thanks,

Alex