Re: [Xen-devel] [PATCH v6] xen/arm: Allow balooning working with 1:1 memory mapping

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 17 Dec 2013, Julien Grall wrote:
> With the lack 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
> devices.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Keir Fraser <keir@xxxxxxx>

Acked-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>


>     Release: This is a bug that prevents DMA-capable devices to work after
>     a guest has started.
> 
>     Changes in v6:
>         - Use # instead of 0x
>         - Make sure that d is evaluated in is_domain_direct_mapped
>     Changes in v5:
>         - Export dom0_11_mapping and transform is_domain_direct_mapped in 
> macro
>         - Add ifndef in common code to define is_domain_direct_mapped
>     Changes in v4:
>         - Fix typoes
>         - Update comment in the code
>     Changes in v3:
>         - Remove spurious page = NULL
>         - Rename is_dom0_mapped_11 to is_domain_direct_mapped
>         - Coding style
>     Changes in v2:
>         - Drop CONFIG_ARM and add is_dom0_mapped_11
> ---
>  xen/arch/arm/domain_build.c  |    2 +-
>  xen/common/memory.c          |   35 ++++++++++++++++++++++++++++++++++-
>  xen/include/asm-arm/domain.h |    3 +++
>  3 files changed, 38 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index faff88e..47b781b 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -22,7 +22,7 @@
>  static unsigned int __initdata opt_dom0_max_vcpus;
>  integer_param("dom0_max_vcpus", opt_dom0_max_vcpus);
>  
> -static int dom0_11_mapping = 1;
> +int dom0_11_mapping = 1;
>  
>  #define DOM0_MEM_DEFAULT 0x8000000 /* 128 MiB */
>  static u64 __initdata dom0_mem = DOM0_MEM_DEFAULT;
> diff --git a/xen/common/memory.c b/xen/common/memory.c
> index eb7b72b..51f11ff 100644
> --- a/xen/common/memory.c
> +++ b/xen/common/memory.c
> @@ -29,6 +29,10 @@
>  #include <xsm/xsm.h>
>  #include <xen/trace.h>
>  
> +#ifndef is_domain_direct_mapped
> +# define is_domain_direct_mapped(d) ((void)(d), 0)
> +#endif
> +
>  struct memop_args {
>      /* INPUT */
>      struct domain *domain;     /* Domain to be affected. */
> @@ -122,7 +126,29 @@ static void populate_physmap(struct memop_args *a)
>          }
>          else
>          {
> -            page = alloc_domheap_pages(d, a->extent_order, a->memflags);
> +            if ( is_domain_direct_mapped(d) )
> +            {
> +                mfn = gpfn;
> +                if ( !mfn_valid(mfn) )
> +                {
> +                    gdprintk(XENLOG_INFO, "Invalid mfn %#"PRI_xen_pfn"\n",
> +                             mfn);
> +                    goto out;
> +                }
> +
> +                page = mfn_to_page(mfn);
> +                if ( !get_page(page, d) )
> +                {
> +                    gdprintk(XENLOG_INFO,
> +                             "mfn %#"PRI_xen_pfn" doesn't belong to the"
> +                             " domain\n", mfn);
> +                    goto out;
> +                }
> +                put_page(page);
> +            }
> +            else
> +                page = alloc_domheap_pages(d, a->extent_order, a->memflags);
> +
>              if ( unlikely(page == NULL) ) 
>              {
>                  if ( !opt_tmem || (a->extent_order != 0) )
> @@ -270,6 +296,13 @@ static void decrease_reservation(struct memop_args *a)
>               && p2m_pod_decrease_reservation(a->domain, gmfn, 
> a->extent_order) )
>              continue;
>  
> +        /* With the lack for iommu on some ARM platform, domain with 
> DMA-capable
> +         * device must retrieve the same pfn when the hypercall
> +         * populate_physmap is called.
> +         */
> +        if ( is_domain_direct_mapped(a->domain) )
> +            continue;
> +
>          for ( j = 0; j < (1 << a->extent_order); j++ )
>              if ( !guest_remove_page(a->domain, gmfn + j) )
>                  goto out;
> diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
> index 28d39a0..e2202a6 100644
> --- a/xen/include/asm-arm/domain.h
> +++ b/xen/include/asm-arm/domain.h
> @@ -86,6 +86,9 @@ enum domain_type {
>  #define is_pv64_domain(d) (0)
>  #endif
>  
> +extern int dom0_11_mapping;
> +#define is_domain_direct_mapped(d) ((d) == dom0 && dom0_11_mapping)
> +
>  struct vtimer {
>          struct vcpu *v;
>          int irq;
> -- 
> 1.7.10.4
> 

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