Re: [Qemu-devel] [RFC PATCH 1/1] nvdimm: let qemu requiring section alignment of pmem resource.

[Stefan Hajnoczi]

On Mon, Jun 11, 2018 at 06:54:25PM +0800, Zhang Yi wrote:
> Nvdimm driver use Memory hot-plug APIs to map it's pmem resource,
> which at a section granularity.
> 
> When QEMU emulated the vNVDIMM device, decrease the label-storage,
> QEMU will put the vNVDIMMs directly next to one another in physical
> address space, which means that the boundary between them won't
> align to the 128 MB memory section size.

I'm having a hard time parsing this.

Where does the "128 MB memory section size" come from?  ACPI?
A chipset-specific value?

> Signed-off-by: Zhang Yi <address@hidden>
> ---
>  hw/mem/nvdimm.c         | 2 +-
>  include/hw/mem/nvdimm.h | 1 +
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/mem/nvdimm.c b/hw/mem/nvdimm.c
> index 4087aca..ff6e171 100644
> --- a/hw/mem/nvdimm.c
> +++ b/hw/mem/nvdimm.c
> @@ -109,7 +109,7 @@ static void nvdimm_realize(PCDIMMDevice *dimm, Error 
> **errp)
>      NVDIMMDevice *nvdimm = NVDIMM(dimm);
>      uint64_t align, pmem_size, size = memory_region_size(mr);
>  
> -    align = memory_region_get_alignment(mr);
> +    align = MAX(memory_region_get_alignment(mr), NVDIMM_ALIGN_SIZE);
>  
>      pmem_size = size - nvdimm->label_size;
>      nvdimm->label_data = memory_region_get_ram_ptr(mr) + pmem_size;
> diff --git a/include/hw/mem/nvdimm.h b/include/hw/mem/nvdimm.h
> index 3c82751..1d384e4 100644
> --- a/include/hw/mem/nvdimm.h
> +++ b/include/hw/mem/nvdimm.h
> @@ -41,6 +41,7 @@
>   *    at least 128KB in size, which holds around 1000 labels."
>   */
>  #define MIN_NAMESPACE_LABEL_SIZE      (128UL << 10)
> +#define NVDIMM_ALIGN_SIZE      (128UL << 20)
>  
>  #define TYPE_NVDIMM      "nvdimm"
>  #define NVDIMM(obj)      OBJECT_CHECK(NVDIMMDevice, (obj), TYPE_NVDIMM)
> -- 
> 2.7.4
>

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