On Fri, 31 Mar 2017 16:41:45 +0800
Haozhong Zhang <haozhong.zh...@intel.com> wrote:
> fsync() is used to persist modifications to the back store. If the
s/back/backing/
> 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.zh...@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);
> + } else {
> + nvdimm->backend_fd = -1;
> + }
> +}
> +
> +void nvdimm_flush(NVDIMMDevice *nvdimm)
> +{
> + if (nvdimm->backend_fd != -1) {
if backend isn't file and user asked for flush_hint, he/she silently won't get
it.
maybe we should fail nvdimm_realize() if backend is not file.
> + /*
> + * If the backend store is a physical NVDIMM device, fsync()
> + * will trigger the flush via the flush hint on the host device.
> + */
> + fsync(nvdimm->backend_fd);
> + }
> +}
> +
> static void nvdimm_realize(PCDIMMDevice *dimm, Error **errp)
> {
> MemoryRegion *mr = host_memory_backend_get_memory(dimm->hostmem, errp);
> @@ -105,6 +125,8 @@ static void nvdimm_realize(PCDIMMDevice *dimm, Error
> **errp)
> memory_region_init_alias(&nvdimm->nvdimm_mr, OBJECT(dimm),
> "nvdimm-memory", mr, 0, pmem_size);
> nvdimm->nvdimm_mr.align = align;
> +
> + nvdimm_flush_init(nvdimm, mr);
> }
>
> /*
> diff --git a/include/hw/mem/nvdimm.h b/include/hw/mem/nvdimm.h
> index 03e1ff9..eb71f41 100644
> --- a/include/hw/mem/nvdimm.h
> +++ b/include/hw/mem/nvdimm.h
> @@ -71,6 +71,18 @@ struct NVDIMMDevice {
> * guest via ACPI NFIT and _FIT method if NVDIMM hotplug is supported.
> */
> MemoryRegion nvdimm_mr;
> +
> + /*
> + * If true, a flush hint address structure will be built for this
> + * NVDIMM device.
> + */
> + bool flush_hint_enabled;
> + /*
> + * File descriptor of the backend store, which is used in nvdimm
> + * flush. It's cached in NVDIMMDevice rather than being fetched
> + * at each request in order to accelerate the flush a little bit.
> + */
> + int backend_fd;
> };
> typedef struct NVDIMMDevice NVDIMMDevice;
>
> @@ -132,4 +144,5 @@ void nvdimm_build_acpi(GArray *table_offsets, GArray
> *table_data,
> uint32_t ram_slots);
> void nvdimm_plug(AcpiNVDIMMState *state);
> void nvdimm_acpi_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev);
> +void nvdimm_flush(NVDIMMDevice *nvdimm);
> #endif
