Re: [Embedded-pv-devel] [Xen-devel] [PATCH RFC 18/18] arm: Add ability to allocate Xen heap in lowmem

[Julien Grall <julien.grall@xxxxxxx>]

Hi Iurii,

On 18/05/16 17:32, Andrii Anisov wrote:
> From: Iurii Konovalenko <iurii.konovalenko@xxxxxxxxxxxxxxx>
>
> Add abiliyty to allocate Xen heap in 32-bit address range for ARM32.
> Due to architecture features some ARM32 platforms require Xen heap
> to be allocated in lowmem.
Can you detail those architecture features? The Xen heap is mostly used 
to allocate memory for Xen itself (i.e not for the guest), so it should 
not be used for any DMA access.
Regards,

> Signed-off-by: Iurii Konovalenko <iurii.konovalenko@xxxxxxxxxxxxxxx>
> ---
>   xen/Rules.mk         |  1 +
>   xen/arch/arm/setup.c | 14 ++++++++++++++
>   2 files changed, 15 insertions(+)
>
> diff --git a/xen/Rules.mk b/xen/Rules.mk
> index 51f7124..30f5227 100644
> --- a/xen/Rules.mk
> +++ b/xen/Rules.mk
> @@ -66,6 +66,7 @@ CFLAGS-$(HAS_PDX)       += -DHAS_PDX
>   CFLAGS-$(frame_pointer) += -fno-omit-frame-pointer -DCONFIG_FRAME_POINTER
>   CFLAGS-$(ARM32_RELOCATE_OVER_4GB) += -DARM32_RELOCATE_OVER_4GB
>   CFLAGS-$(ARM32_SEPAR_MEM_SPLIT) += -DARM32_SEPAR_MEM_SPLIT
> +CFLAGS-$(ARM32_XENHEAP_IN_LOWMEM) += -DARM32_XENHEAP_IN_LOWMEM
>
>   ifneq ($(max_phys_cpus),)
>   CFLAGS-y                += -DMAX_PHYS_CPUS=$(max_phys_cpus)
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 7e507bc..5510a34 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -475,7 +475,11 @@ static void init_pdx(void)
>   #ifdef CONFIG_ARM_32
>   static void __init setup_mm(unsigned long dtb_paddr, size_t dtb_size)
>   {
> +#ifdef ARM32_XENHEAP_IN_LOWMEM
> +    paddr_t ram_start, ram_end, ram_size, dma32_end;
> +#else
>       paddr_t ram_start, ram_end, ram_size;
> +#endif
>       paddr_t s, e;
>       unsigned long ram_pages;
>       unsigned long heap_pages, xenheap_pages, domheap_pages;
> @@ -492,6 +496,9 @@ static void __init setup_mm(unsigned long dtb_paddr, size_t 
> dtb_size)
>       ram_start = bootinfo.mem.bank[0].start;
>       ram_size  = bootinfo.mem.bank[0].size;
>       ram_end   = ram_start + ram_size;
> +#ifdef ARM32_XENHEAP_IN_LOWMEM
> +    dma32_end = ram_end > 0x100000000ULL ? 0 : ram_end;
> +#endif
>
>       for ( i = 1; i < bootinfo.mem.nr_banks; i++ )
>       {
> @@ -502,6 +509,9 @@ static void __init setup_mm(unsigned long dtb_paddr, size_t 
> dtb_size)
>           ram_size  = ram_size + bank_size;
>           ram_start = min(ram_start,bank_start);
>           ram_end   = max(ram_end,bank_end);
> +#ifdef ARM32_XENHEAP_IN_LOWMEM
> +        dma32_end = bank_end > 0x100000000ULL ? dma32_end : bank_end;
> +#endif
>       }
>
>       total_pages = ram_pages = ram_size >> PAGE_SHIFT;
> @@ -530,7 +540,11 @@ static void __init setup_mm(unsigned long dtb_paddr, 
> size_t dtb_size)
>
>       do
>       {
> +#ifdef ARM32_XENHEAP_IN_LOWMEM
> +        e = consider_modules(ram_start, dma32_end,
> +#else
>           e = consider_modules(ram_start, ram_end,
> +#endif
>                                pfn_to_paddr(xenheap_pages),
>                                32<<20, 0);
>           if ( e )
--
Julien Grall

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