Re: [Xen-devel] [PATCH] xen/arm: Allow balooning working with 1:1 memory mapping

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 14 Nov 2013, Julien Grall wrote:
> With the lake of iommu, dom0 must have a 1:1 memory mapping for all
> these guest physical address. When the ballon decides to give back a
> page to the kernel, this page must have the same address as previously.
> Otherwise, we will loose the 1:1 mapping and will break DMA-capable
> device.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> CC: Keir Fraser <keir@xxxxxxx>
> CC: Jan Beulich <jbeulich@xxxxxxxx>
> ---
>  xen/common/memory.c | 42 ++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 40 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/common/memory.c b/xen/common/memory.c
> index 50b740f..df36d43 100644
> --- a/xen/common/memory.c
> +++ b/xen/common/memory.c
> @@ -28,6 +28,9 @@
>  #include <public/memory.h>
>  #include <xsm/xsm.h>
>  #include <xen/trace.h>
> +#ifdef CONFIG_ARM
> +#include <asm/platform.h>
> +#endif
>  
>  struct memop_args {
>      /* INPUT */
> @@ -90,7 +93,7 @@ static void increase_reservation(struct memop_args *a)
>  
>  static void populate_physmap(struct memop_args *a)
>  {
> -    struct page_info *page;
> +    struct page_info *page = NULL;
>      unsigned long i, j;
>      xen_pfn_t gpfn, mfn;
>      struct domain *d = a->domain;
> @@ -122,7 +125,33 @@ static void populate_physmap(struct memop_args *a)
>          }
>          else
>          {
> -            page = alloc_domheap_pages(d, a->extent_order, a->memflags);
> +#ifdef CONFIG_ARM
> +            if ( d == dom0 && 
> platform_has_quirk(PLATFORM_QUIRK_DOM0_MAPPING_11) )
> +            {
> +                mfn = gpfn;
> +                if (!mfn_valid(mfn))
> +                {
> +                    gdprintk(XENLOG_INFO, "Invalid mfn 0x%"PRI_xen_pfn"\n",
> +                             mfn);
> +                    goto out;
> +                }
> +
> +                page = mfn_to_page(mfn);
> +                if ( !get_page(page, d) )
> +                {
> +                    gdprintk(XENLOG_INFO,
> +                             "mfn 0x%"PRI_xen_pfn" doesn't belong to dom0\n",
> +                             mfn);
> +                    goto out;
> +                }
> +                put_page(page);
> +            }
> +            else
> +#endif

I don't know if the x86 maintainers would like that, but I would prefer
to remove the ifdef CONFIG_ARM.
You just need to define a new function called is_dom0_mapped_11, that
always returns false on x86 and on ARM is implemented by d == dom0 &&
platform_has_quirk(PLATFORM_QUIRK_DOM0_MAPPING_11).
Then you can use it on common code.


> +            {
> +                page = alloc_domheap_pages(d, a->extent_order, a->memflags);
> +            }
> +
>              if ( unlikely(page == NULL) ) 
>              {
>                  if ( !opt_tmem || (a->extent_order != 0) )
> @@ -270,6 +299,15 @@ static void decrease_reservation(struct memop_args *a)
>               && p2m_pod_decrease_reservation(a->domain, gmfn, 
> a->extent_order) )
>              continue;
>  
> +#ifdef CONFIG_ARM
> +        /* With the lake for iommu, dom0 must retrieve the same pfn when
> +         * the hypercall populate_physmap is called.
> +         */
> +        if ( a->domain == dom0 &&
> +             platform_has_quirk(PLATFORM_QUIRK_DOM0_MAPPING_11) )
> +            continue;
> +#endif
> +
>          for ( j = 0; j < (1 << a->extent_order); j++ )
>              if ( !guest_remove_page(a->domain, gmfn + j) )
>                  goto out;
> -- 
> 1.8.3.1
> 

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