[Xen-devel] Re: [PATCH] Enable PCI passthrough with stub domain.

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

One major point of stubdomains is to deprivilege qemu. If we give it access
to domctls like {memory,ioport}_mapping it's rather defeating that purpose.
Perhaps some thought is needed as to how PCI passthru is architected -- the
actual setting up of access permissions (which is implicitly what some of
those domctls do) should be done by the toolstack and/or pciback, both of
which continue to reside in dom0.

 -- Keir

On 09/01/2009 10:08, "Shohei Fujiwara" <fujiwara-sxa@xxxxxxxxxxxxxxx> wrote:

> This patch enables PCI passthrough with stub domain.
> 
> PCI passthrough with stub domain has failed in the past.
> The primary reason is that hypercalls from qemu in stub domain are rejected.
> 
> This patch allows qemu in stub domain to call the hypercalls which is
> needed for PCI passthrough. For security, if target domain of
> hypercall is different from that of stub domain, it rejects hypercall.
> 
> To use PCI passthrough, please configure pciback driver to be
> permissive, because qemu has own virtualization code for PCI
> passthrough. For example:
> 
>     # cd /sys/bus/pci/drivers/pciback
>     # echo "0000:0d:00.0" > permissive
> 
> Currently Linux guest only works.
> But Windows guest doesn't work, so I'm debugging for now.
> I hope this patch will be useful for other developers in community.
> 
> Thanks,
> --
> Shohei Fujiwara.
> 
> 
> Signed-off-by: Shohei Fujiwara <fujiwara-sxa@xxxxxxxxxxxxxxx>
> 
> diff -r b9721b2766c1 xen/arch/x86/irq.c
> --- a/xen/arch/x86/irq.c Wed Jan 07 11:25:00 2009 +0000
> +++ b/xen/arch/x86/irq.c Thu Jan 08 18:58:36 2009 +0900
> @@ -857,7 +857,7 @@ int map_domain_pirq(
>      if ( type == MAP_PIRQ_TYPE_MSI )
>          return -EINVAL;
>  
> -    if ( !IS_PRIV(current->domain) )
> +    if ( !IS_PRIV_FOR(current->domain, d) )
>          return -EPERM;
>  
>      if ( pirq < 0 || pirq >= NR_IRQS || vector < 0 || vector >= NR_VECTORS )
> @@ -931,7 +931,7 @@ int unmap_domain_pirq(struct domain *d,
>      if ( (pirq < 0) || (pirq >= NR_IRQS) )
>          return -EINVAL;
>  
> -    if ( !IS_PRIV(current->domain) )
> +    if ( !IS_PRIV_FOR(current->domain, d) )
>          return -EINVAL;
>  
>      ASSERT(spin_is_locked(&pcidevs_lock));
> diff -r b9721b2766c1 xen/arch/x86/physdev.c
> --- a/xen/arch/x86/physdev.c Wed Jan 07 11:25:00 2009 +0000
> +++ b/xen/arch/x86/physdev.c Thu Jan 08 18:58:36 2009 +0900
> @@ -34,9 +34,6 @@ static int physdev_map_pirq(struct physd
>      struct msi_info _msi;
>      void *map_data = NULL;
>  
> -    if ( !IS_PRIV(current->domain) )
> -        return -EPERM;
> -
>      if ( !map )
>          return -EINVAL;
>  
> @@ -49,6 +46,14 @@ static int physdev_map_pirq(struct physd
>      {
>          ret = -ESRCH;
>          goto free_domain;
> +    }
> +    else
> +    {
> +        if ( !IS_PRIV_FOR(current->domain, d) )
> +        {
> +            ret = -EPERM;
> +            goto free_domain;
> +        }
>      }
>  
>      /* Verify or get vector. */
> @@ -161,8 +166,8 @@ static int physdev_unmap_pirq(struct phy
>      struct domain *d;
>      int ret;
>  
> -    if ( !IS_PRIV(current->domain) )
> -        return -EPERM;
> +    if ( !unmap )
> +        return -EINVAL;
>  
>      if ( unmap->domid == DOMID_SELF )
>          d = rcu_lock_domain(current->domain);
> @@ -171,6 +176,14 @@ static int physdev_unmap_pirq(struct phy
>  
>      if ( d == NULL )
>          return -ESRCH;
> +    else
> +    {
> +        if ( !IS_PRIV_FOR(current->domain, d) )
> +        {
> +            rcu_unlock_domain(d);
> +            return -EPERM;
> +        }
> +    }
>  
>      spin_lock(&pcidevs_lock);
>      spin_lock(&d->event_lock);
> diff -r b9721b2766c1 xen/common/domctl.c
> --- a/xen/common/domctl.c Wed Jan 07 11:25:00 2009 +0000
> +++ b/xen/common/domctl.c Thu Jan 08 18:58:36 2009 +0900
> @@ -193,14 +193,49 @@ long do_domctl(XEN_GUEST_HANDLE(xen_domc
>      long ret = 0;
>      struct xen_domctl curop, *op = &curop;
>  
> -    if ( !IS_PRIV(current->domain) )
> -        return -EPERM;
> -
>      if ( copy_from_guest(op, u_domctl, 1) )
>          return -EFAULT;
>  
>      if ( op->interface_version != XEN_DOMCTL_INTERFACE_VERSION )
>          return -EACCES;
> +
> +    switch ( op->cmd )
> +    {
> +    case XEN_DOMCTL_pin_mem_cacheattr:
> +    case XEN_DOMCTL_memory_mapping:
> +    case XEN_DOMCTL_ioport_mapping:
> +    case XEN_DOMCTL_assign_device:
> +    case XEN_DOMCTL_deassign_device:
> +    case XEN_DOMCTL_bind_pt_irq:
> +    case XEN_DOMCTL_unbind_pt_irq:
> +    {
> +        struct domain *d;
> +
> +        if ( op->domain != DOMID_SELF )
> +        {
> +            d = rcu_lock_domain_by_id(op->domain);
> +
> +            if ( d == NULL )
> +                return -ESRCH;
> +            else
> +            {
> +                if ( !IS_PRIV_FOR(current->domain, d) )
> +                {
> +                    rcu_unlock_domain(d);
> +                    return -EPERM;
> +                }
> +                else
> +                    rcu_unlock_domain(d);
> +            }
> +            break;
> +        }
> +    }
> +
> +    default:
> +        if ( !IS_PRIV(current->domain) )
> +            return -EPERM;
> +        break;
> +    }
>  
>      spin_lock(&domctl_lock);
>  



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