Re: [Xen-devel] [PATCH] x86/p2m: fix non-translated handling of iommu mappings

[Roman Shaposhnik <roman@xxxxxxxxxx>]

On Mon, Jul 22, 2019 at 8:33 AM Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
>
> The current usage of need_iommu_pt_sync in p2m for non-translated
> guests is wrong because it doesn't correctly handle a relaxed PV
> hardware domain, that has need_sync set to false, but still need
> entries to be added from calls to {set/clear}_identity_p2m_entry.
>
> Adjust the code in guest_physmap_add_page to also check whether the
> domain has an iommu instead of whether it needs syncing or not in
> order to take a reference to a page to be mapped.
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: Wei Liu <wl@xxxxxxx>
> Cc: Paul Durrant <Paul.Durrant@xxxxxxxxxx>

Tested-by: Roman Shaposhnik <roman@xxxxxxxxxx>

> ---
>  xen/arch/x86/mm/p2m.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index fef97c82f6..88a2430c8c 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -836,7 +836,7 @@ guest_physmap_add_page(struct domain *d, gfn_t gfn, mfn_t 
> mfn,
>           */
>          for ( i = 0; i < (1UL << page_order); ++i, ++page )
>          {
> -            if ( !need_iommu_pt_sync(d) )
> +            if ( !has_iommu_pt(d) )
>                  /* nothing */;
>              else if ( get_page_and_type(page, d, PGT_writable_page) )
>                  put_page_and_type(page);
> @@ -1341,7 +1341,7 @@ int set_identity_p2m_entry(struct domain *d, unsigned 
> long gfn_l,
>
>      if ( !paging_mode_translate(p2m->domain) )
>      {
> -        if ( !need_iommu_pt_sync(d) )
> +        if ( !has_iommu_pt(d) )
>              return 0;
>          return iommu_legacy_map(d, _dfn(gfn_l), _mfn(gfn_l), PAGE_ORDER_4K,
>                                  IOMMUF_readable | IOMMUF_writable);
> @@ -1432,7 +1432,7 @@ int clear_identity_p2m_entry(struct domain *d, unsigned 
> long gfn_l)
>
>      if ( !paging_mode_translate(d) )
>      {
> -        if ( !need_iommu_pt_sync(d) )
> +        if ( !has_iommu_pt(d) )
>              return 0;
>          return iommu_legacy_unmap(d, _dfn(gfn_l), PAGE_ORDER_4K);
>      }
> --
> 2.20.1 (Apple Git-117)
>
>
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