Re: [Xen-devel] [PATCH v3] xen/arm: Allow balooning working with 1:1 memory mapping

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-12-16 at 15:45 +0000, 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
> devices.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> Cc: Keir Fraser <keir@xxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> 
> ---
>     Release: This is a bug that prevents DMA-capable devices to work after
>     a guest has started.
> 
>     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  |    5 +++++
>  xen/common/memory.c          |   30 +++++++++++++++++++++++++++++-
>  xen/include/asm-arm/domain.h |    2 ++
>  xen/include/asm-x86/domain.h |    2 ++
>  4 files changed, 38 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index faff88e..2bbee36 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -65,6 +65,11 @@ struct vcpu *__init alloc_dom0_vcpu0(void)
>      return alloc_vcpu(dom0, 0, 0);
>  }
>  
> +int is_domain_direct_mapped(struct domain *d)
> +{
> +    return (dom0_11_mapping && d == dom0);
> +}
> +
>  static void allocate_memory_11(struct domain *d, struct kernel_info *kinfo)
>  {
>      paddr_t start;
> diff --git a/xen/common/memory.c b/xen/common/memory.c
> index 61791a4..45dbf07 100644
> --- a/xen/common/memory.c
> +++ b/xen/common/memory.c
> @@ -122,7 +122,29 @@ 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 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",

With the new setup d is not necessarily dom0.

> +                             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 +292,12 @@ static void decrease_reservation(struct memop_args *a)
>               && p2m_pod_decrease_reservation(a->domain, gmfn, 
> a->extent_order) )
>              continue;
>  
> +        /* With the lake for iommu on some ARM platform, dom0 must retrieve

s/lake/lack/ and another stray reference to dom0.

> +         * 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..dbc1389 100644
> --- a/xen/include/asm-arm/domain.h
> +++ b/xen/include/asm-arm/domain.h
> @@ -86,6 +86,8 @@ enum domain_type {
>  #define is_pv64_domain(d) (0)
>  #endif
>  
> +int is_domain_direct_mapped(struct domain *d);
> +
>  struct vtimer {
>          struct vcpu *v;
>          int irq;
> diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
> index 9d39061..2c7f809 100644
> --- a/xen/include/asm-x86/domain.h
> +++ b/xen/include/asm-x86/domain.h
> @@ -16,6 +16,8 @@
>  #define is_pv_32on64_domain(d) (is_pv_32bit_domain(d))
>  #define is_pv_32on64_vcpu(v)   (is_pv_32on64_domain((v)->domain))
>  
> +#define is_domain_direct_mapped(d) (0)
> +
>  #define is_hvm_pv_evtchn_domain(d) (has_hvm_container_domain(d) && \
>          d->arch.hvm_domain.irq.callback_via_type == HVMIRQ_callback_vector)
>  #define is_hvm_pv_evtchn_vcpu(v) (is_hvm_pv_evtchn_domain(v->domain))



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