From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@suse.com>
Subject: Re: [v7][PATCH 15/16] xen/vtd: prevent from assign the
 device with shared rmrr
Date: Mon, 13 Jul 2015 14:41:29 +0100
Message-ID: <55A3DC29020000780009037A@mail.emea.novell.com>
References: <1436420047-25356-1-git-send-email-tiejun.chen@intel.com>
	<1436420047-25356-16-git-send-email-tiejun.chen@intel.com>
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To: Tiejun Chen <tiejun.chen@intel.com>
Cc: Yang Zhang <yang.z.zhang@intel.com>, Kevin Tian <kevin.tian@intel.com>, xen-devel@lists.xen.org
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>>> On 09.07.15 at 07:34, <tiejun.chen@intel.com> wrote:
> --- a/xen/drivers/passthrough/vtd/iommu.c
> +++ b/xen/drivers/passthrough/vtd/iommu.c
> @@ -2297,13 +2297,39 @@ 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: 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 )
> +            {
> +                printk(XENLOG_G_ERR VTDPREFIX
> +                       " cannot assign %04x:%02x:%02x.%u"
> +                       " with shared RMRR for Dom%d.\n",
> +                       seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn),
> +                       d->domain_id);
> +                return -EPERM;
> +            }
> +        }

Two if()-s like these should be folded into one.

In your place I'd also consider also printing the RMRR base address
for easier analysis of the issue.

Jan