Re: [PATCH v5 4/7] xen/arm: static memory initialization

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 24 Aug 2021, Penny Zheng wrote:
> This patch introduces static memory initialization, during system boot up.
> 
> The new function init_staticmem_pages is responsible for static memory
> initialization.
> 
> Helper free_staticmem_pages is the equivalent of free_heap_pages, to free
> nr_mfns pages of static memory.
> 
> This commit also introduces new CONFIG_STATIC_MEMORY to wrap all
                              ^ a                     ^ option

> static-allocation-related codes.
                            ^ code

> Put asynchronous scrubbing for pages of static memory in TODO list.
> 
> Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
> ---
> v5 change:
> - make CONFIG_STATIC_MEMORY user selectable and gated by UNSUPPORTED.
> - wrap all static-allocation-related codes with CONFIG_STATIC_MEMORY
> even in arm-specific file.
> - make bank_start/bank_end type of mfn_t, and rename bank_size to
> bank_pages.
> ---
>  xen/arch/arm/setup.c    | 31 +++++++++++++++++++++++++++++++
>  xen/common/Kconfig      | 17 +++++++++++++++++
>  xen/common/page_alloc.c | 22 +++++++++++++++++++++-
>  xen/include/xen/mm.h    |  6 ++++++
>  4 files changed, 75 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 63a908e325..44aca9f1b9 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -609,6 +609,29 @@ static void __init init_pdx(void)
>      }
>  }
>  
> +#ifdef CONFIG_STATIC_MEMORY
> +/* Static memory initialization */
> +static void __init init_staticmem_pages(void)
> +{
> +    unsigned int bank;
> +
> +    for ( bank = 0 ; bank < bootinfo.reserved_mem.nr_banks; bank++ )
> +    {
> +        if ( bootinfo.reserved_mem.bank[bank].xen_domain )
> +        {
> +            mfn_t bank_start = 
> _mfn(PFN_UP(bootinfo.reserved_mem.bank[bank].start));
> +            unsigned long bank_pages = 
> PFN_DOWN(bootinfo.reserved_mem.bank[bank].size);
> +            mfn_t bank_end = mfn_add(bank_start, bank_pages);
> +
> +            if ( mfn_x(bank_end) <= mfn_x(bank_start) )
> +                return;
> +
> +            free_staticmem_pages(mfn_to_page(bank_start), bank_pages, false);
> +        }
> +    }
> +}
> +#endif
> +
>  #ifdef CONFIG_ARM_32
>  static void __init setup_mm(void)
>  {
> @@ -736,6 +759,10 @@ static void __init setup_mm(void)
>      /* Add xenheap memory that was not already added to the boot allocator. 
> */
>      init_xenheap_pages(mfn_to_maddr(xenheap_mfn_start),
>                         mfn_to_maddr(xenheap_mfn_end));
> +
> +#ifdef CONFIG_STATIC_MEMORY
> +    init_staticmem_pages();
> +#endif
>  }
>  #else /* CONFIG_ARM_64 */
>  static void __init setup_mm(void)
> @@ -789,6 +816,10 @@ static void __init setup_mm(void)
>  
>      setup_frametable_mappings(ram_start, ram_end);
>      max_page = PFN_DOWN(ram_end);
> +
> +#ifdef CONFIG_STATIC_MEMORY
> +    init_staticmem_pages();
> +#endif
>  }
>  #endif
>  
> diff --git a/xen/common/Kconfig b/xen/common/Kconfig
> index 0ddd18e11a..514a2c9022 100644
> --- a/xen/common/Kconfig
> +++ b/xen/common/Kconfig
> @@ -67,6 +67,23 @@ config MEM_ACCESS
>  config NEEDS_LIBELF
>       bool
>  
> +config STATIC_MEMORY
> +        bool "Static Allocation Support (UNSUPPORTED)" if UNSUPPORTED
> +     depends on ARM
> +     ---help---
> +       Static Allocation refers to system or sub-system(domains) for
> +       which memory areas are pre-defined by configuration using physical
> +          address ranges.
> +
> +       Those pre-defined memory, -- Static Memory, as parts of RAM reserved
> +       during system boot-up, shall never go to heap allocator or boot
> +       allocator for any use.
> +
> +       When enabled, memory can be statically allocated to a domain using
> +       the property "xen,static-mem" defined in the domain configuration.
> +
> +       If unsure, say Y.

I share Jan's comment about indentation, the kconfig message and the
little spurious change below. Aside from those, this patch looks fine to
me.