Re: [Xen-devel] [PATCH v2] x86/vtd: fix iommu_share_p2m_table

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Roger Pau Monne [mailto:roger.pau@xxxxxxxxxx]
> Sent: 08 October 2018 14:53
> To: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Roger Pau Monne <roger.pau@xxxxxxxxxx>; Jan Beulich
> <jbeulich@xxxxxxxx>; Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> Subject: [PATCH v2] x86/vtd: fix iommu_share_p2m_table
> 
> Commit 2916951c1 "mm / iommu: include need_iommu() test in
> iommu_use_hap_pt()" changed the check in iommu_share_p2m_table to use
> need_iommu(d) (as part of iommu_use_hap_pt) instead of iommu_enabled,
> which broke the check because at the point in domain construction
> where iommu_share_p2m_table is called need_iommu(d) will always return
> false.
> 
> Fix this by reverting to the previous logic.
> 
> While there turn the hap_enabled check into an ASSERT, since the only
> caller of iommu_share_p2m_table already performs the hap_enabled check
> before calling the function.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

> ---
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Paul Durrant <paul.durrant@xxxxxxxxxx>
> ---
> Changes since v1:
>  - Add a comment about why iommu_use_hap_pt cannot be used in
>    iommu_share_p2m_table.
>  - Expand commit message.
>  - Convert the hap_enabled check into an ASSERT.
> ---
>  xen/drivers/passthrough/iommu.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/drivers/passthrough/iommu.c
> b/xen/drivers/passthrough/iommu.c
> index debb5e6fe1..75bc410c2c 100644
> --- a/xen/drivers/passthrough/iommu.c
> +++ b/xen/drivers/passthrough/iommu.c
> @@ -505,7 +505,13 @@ int iommu_do_domctl(
> 
>  void iommu_share_p2m_table(struct domain* d)
>  {
> -    if ( iommu_use_hap_pt(d) )
> +    ASSERT(hap_enabled(d));
> +    /*
> +     * iommu_use_hap_pt cannot be used here because at the point in the
> domain
> +     * construction where iommu_share_p2m_table get called need_iommu(d)
> will
> +     * always return false.
> +     */
> +    if ( iommu_enabled && iommu_hap_pt_share )
>          iommu_get_ops()->share_p2m(d);
>  }
> 
> --
> 2.19.0

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel