Subject: Re: [PATCH V1 mlx5-next 11/13] vfio/mlx5: Implement vfio_pci driver for mlx5 devices

From: Jason Gunthorpe <[email-masked]>
Date: Mon, 18 Oct 2021 08:51:07 -0300

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 <[email-masked]> 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 <[email-masked]> 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;

This is my preference:

if (vmig->vfio_dev_state != VFIO_DEVICE_STATE_ERROR ||
    !vfio_device_state_valid(state) ||
    (state & !MLX5VF_SUPPORTED_DEVICE_STATES))

> 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