Re: [Xen-devel] [v3][PATCH 16/16] xen/vtd: prevent from assign the device with shared rmrr

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Chen, Tiejun
> Sent: Thursday, June 11, 2015 9:15 AM
> 
> Currently we're intending to cover this kind of devices

we're -> we're not?

> with shared RMRR simply since the case of shared RMRR is
> a rare case according to our previous experiences. But
> late we can group these devices which shared rmrr, and
> then allow all devices within a group to be assigned to
> same domain.
> 
> Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>

Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx> except one text
comment.

> ---
>  xen/drivers/passthrough/vtd/iommu.c | 30
> +++++++++++++++++++++++++++---
>  1 file changed, 27 insertions(+), 3 deletions(-)
> 
> diff --git a/xen/drivers/passthrough/vtd/iommu.c
> b/xen/drivers/passthrough/vtd/iommu.c
> index d3233b8..f220081 100644
> --- a/xen/drivers/passthrough/vtd/iommu.c
> +++ b/xen/drivers/passthrough/vtd/iommu.c
> @@ -2277,13 +2277,37 @@ static int intel_iommu_assign_device(
>      if ( list_empty(&acpi_drhd_units) )
>          return -ENODEV;
> 
> +    seg = pdev->seg;
> +    bus = pdev->bus;
> +    /*
> +     * In rare cases one given rmrr is shared by multiple devices but
> +     * obviously this would put the security of a system at risk. So
> +     * we should prevent from this sort of device assignment.
> +     *
> +     * TODO: actually we can group these devices which shared rmrr, and
> +     * then allow all devices within a group to be assigned to same domain.

TODO: in the future we can introduce group device assignment
interface to make sure devices sharing RMRR are assigned to the 
same domain together.

> +     */
> +    for_each_rmrr_device( rmrr, bdf, i )
> +    {
> +        if ( rmrr->segment == seg &&
> +             PCI_BUS(bdf) == bus &&
> +             PCI_DEVFN2(bdf) == devfn )
> +        {
> +            if ( rmrr->scope.devices_cnt > 1 )
> +            {
> +                ret = -EPERM;
> +                printk(XENLOG_G_ERR VTDPREFIX
> +                       " cannot assign this device with shared RMRR for 
> Dom%d (%d)\n",
> +                       d->domain_id, ret);
> +                return ret;
> +            }
> +        }
> +    }
> +
>      ret = reassign_device_ownership(hardware_domain, d, devfn, pdev);
>      if ( ret )
>          return ret;
> 
> -    seg = pdev->seg;
> -    bus = pdev->bus;
> -
>      /* Setup rmrr identity mapping */
>      for_each_rmrr_device( rmrr, bdf, i )
>      {
> --
> 1.9.1


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