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References: <20170331084147.32716-1-haozhong.zhang@intel.com>
	<20170331084147.32716-3-haozhong.zhang@intel.com>
From: Xiao Guangrong <guangrong.xiao@gmail.com>
Message-ID: <ad9c678b-5859-e54c-2eb6-06d458a41312@gmail.com>
Date: Thu, 6 Apr 2017 19:52:25 +0800
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Subject: Re: [Qemu-devel] [RFC PATCH 2/4] nvdimm: add functions to
 initialize and perform flush on back store
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To: Haozhong Zhang <haozhong.zhang@intel.com>, qemu-devel@nongnu.org
Cc: dan.j.williams@intel.com, Xiao Guangrong <xiaoguangrong.eric@gmail.com>, Igor Mammedov <imammedo@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>



On 03/31/2017 04:41 PM, Haozhong Zhang wrote:
> fsync() is used to persist modifications to the back store. If the
> host NVDIMM is used as the back store, fsync() on Linux will trigger
> the write to the host flush hint address.
>
> Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
> ---
>  hw/mem/nvdimm.c         | 22 ++++++++++++++++++++++
>  include/hw/mem/nvdimm.h | 13 +++++++++++++
>  2 files changed, 35 insertions(+)
>
> diff --git a/hw/mem/nvdimm.c b/hw/mem/nvdimm.c
> index db896b0..484ab8b 100644
> --- a/hw/mem/nvdimm.c
> +++ b/hw/mem/nvdimm.c
> @@ -78,6 +78,26 @@ static MemoryRegion *nvdimm_get_memory_region(PCDIMMDevice *dimm)
>      return &nvdimm->nvdimm_mr;
>  }
>
> +static void nvdimm_flush_init(NVDIMMDevice *nvdimm, MemoryRegion *hostmem_mr)
> +{
> +    if (nvdimm->flush_hint_enabled) {
> +        nvdimm->backend_fd = memory_region_get_fd(hostmem_mr);

Hmm, IIRC host-mem-file does not initalize backend_fd at all.