Re: [PATCH v5 2/2] xen/arm: allow translated iommu mappings

[Julien Grall <julien@xxxxxxx>]

Hi,

On 25/07/2025 15:01, Stewart Hildebrand wrote:
> From: Stefano Stabellini <stefano.stabellini@xxxxxxx>
>
> In preparation of exposing vITS to domUs, generalize arm_iommu_map_page
> and arm_iommu_unmap_page to allow ITS doorbell mappings with dfn != mfn.
>
> The mfn does not need to be passed to guest_physmap_remove_page since
> there is no mfn checking on the p2m_iommu_map_{rw,ro} p2m types during
> unmap. Pass INVALID_MFN to guest_physmap_remove_page.
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>

> ---
> v4->v5:
> * no change
>
> v3->v4:
> * no change
>
> v2->v3:
> * split change from ("xen/arm: fix arm_iommu_map_page after f9f6b22ab")
> * both map and unmap
> ---
>   xen/drivers/passthrough/arm/iommu_helpers.c | 11 ++---------
>   1 file changed, 2 insertions(+), 9 deletions(-)
>
> diff --git a/xen/drivers/passthrough/arm/iommu_helpers.c 
> b/xen/drivers/passthrough/arm/iommu_helpers.c
> index bdb271584b0d..a3e3cafb8705 100644
> --- a/xen/drivers/passthrough/arm/iommu_helpers.c
> +++ b/xen/drivers/passthrough/arm/iommu_helpers.c
> @@ -36,9 +36,6 @@ int __must_check arm_iommu_map_page(struct domain *d, dfn_t 
> dfn, mfn_t mfn,
>   {
>       p2m_type_t t;
>   
> -    BUG_ON(!domain_use_host_layout(d));
> -    BUG_ON(mfn_x(mfn) != dfn_x(dfn));
> -
>       /* We only support readable and writable flags */
>       if ( !(flags & (IOMMUF_readable | IOMMUF_writable)) )
>           return -EINVAL;
> @@ -49,7 +46,7 @@ int __must_check arm_iommu_map_page(struct domain *d, dfn_t 
> dfn, mfn_t mfn,
>        * The function guest_physmap_add_entry replaces the current mapping
>        * if there is already one...
>        */
> -    return guest_physmap_add_entry(d, _gfn(dfn_x(dfn)), _mfn(dfn_x(dfn)),
> +    return guest_physmap_add_entry(d, _gfn(dfn_x(dfn)), mfn,
>                                      IOMMUF_order(flags), t);
>   }
>   
> @@ -58,11 +55,7 @@ int __must_check arm_iommu_unmap_page(struct domain *d, dfn_t dfn,
>                                         unsigned int order,
>                                         unsigned int *flush_flags)
>   {
> -    if ( !domain_use_host_layout(d) )
> -        return -EINVAL;
> -
> -    return guest_physmap_remove_page(d, _gfn(dfn_x(dfn)), _mfn(dfn_x(dfn)),
> -                                     order);
> +    return guest_physmap_remove_page(d, _gfn(dfn_x(dfn)), INVALID_MFN, order);
>   }
>   
>   /*
--
Julien Grall