Re: [Qemu-devel] [PATCH v4 1/3] nvdimm acpi: introduce fit buffer

[Igor Mammedov <imammedo@redhat.com>]

On Thu,  3 Nov 2016 11:51:28 +0800
Xiao Guangrong <guangrong.xiao@linux.intel.com> wrote:

> The buffer is used to save the FIT info for all the presented nvdimm
> devices which is updated after the nvdimm device is plugged or
> unplugged. In the later patch, it will be used to construct NVDIMM
> ACPI _FIT method which reflects the presented nvdimm devices after
> nvdimm hotplug
> 
> As FIT buffer can not completely mapped into guest address space,
> OSPM will exit to QEMU multiple times, however, there is the race
> condition - FIT may be changed during these multiple exits, so that
> we mark @dirty whenever the buffer is updated.
> 
> @dirty is cleared for the first time OSPM gets fit buffer, if
> dirty is detected in the later access, OSPM will restart the
> access
> 
> Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
> ---
>  hw/acpi/nvdimm.c        | 57 ++++++++++++++++++++++++++++++-------------------
>  hw/i386/acpi-build.c    |  2 +-
>  hw/i386/pc.c            |  4 ++++
>  include/hw/mem/nvdimm.h | 21 +++++++++++++++++-
>  4 files changed, 60 insertions(+), 24 deletions(-)
> 
> diff --git a/hw/acpi/nvdimm.c b/hw/acpi/nvdimm.c
> index b8a2e62..9fee077 100644
> --- a/hw/acpi/nvdimm.c
> +++ b/hw/acpi/nvdimm.c
> @@ -38,11 +38,7 @@ static int nvdimm_plugged_device_list(Object *obj, void *opaque)
s/nvdimm_plugged_device_list/nvdimm_device_list/

>      GSList **list = opaque;
>  
>      if (object_dynamic_cast(obj, TYPE_NVDIMM)) {
> -        DeviceState *dev = DEVICE(obj);
> -
> -        if (dev->realized) { /* only realized NVDIMMs matter */
> -            *list = g_slist_append(*list, DEVICE(obj));
> -        }
> +        *list = g_slist_append(*list, DEVICE(obj));
>      }
>  
>      object_child_foreach(obj, nvdimm_plugged_device_list, opaque);
> @@ -348,8 +344,9 @@ static void nvdimm_build_structure_dcr(GArray *structures, DeviceState *dev)
>                                           (DSM) in DSM Spec Rev1.*/);
>  }
>  
> -static GArray *nvdimm_build_device_structure(GSList *device_list)
> +static GArray *nvdimm_build_device_structure(void)
>  {
> +    GSList *device_list = nvdimm_get_plugged_device_list();
>      GArray *structures = g_array_new(false, true /* clear */, 1);
>  
>      for (; device_list; device_list = device_list->next) {
> @@ -367,28 +364,50 @@ static GArray *nvdimm_build_device_structure(GSList *device_list)
>          /* build NVDIMM Control Region Structure. */
>          nvdimm_build_structure_dcr(structures, dev);
>      }
> +    g_slist_free(device_list);
>  
>      return structures;
>  }
>  
> -static void nvdimm_build_nfit(GSList *device_list, GArray *table_offsets,
> +static void nvdimm_init_fit_buffer(NvdimmFitBuffer *fit_buf)
> +{
> +    fit_buf->fit = g_array_new(false, true /* clear */, 1);
> +}
> +
> +static void nvdimm_build_fit_buffer(NvdimmFitBuffer *fit_buf)
> +{
> +    g_array_free(fit_buf->fit, true);
> +    fit_buf->fit = nvdimm_build_device_structure();
> +    fit_buf->dirty = true;
> +}
> +
> +void nvdimm_acpi_hotplug(AcpiNVDIMMState *state)
> +{
> +    nvdimm_build_fit_buffer(&state->fit_buf);
> +}
> +
> +static void nvdimm_build_nfit(AcpiNVDIMMState *state, GArray *table_offsets,
>                                GArray *table_data, BIOSLinker *linker)
>  {
> -    GArray *structures = nvdimm_build_device_structure(device_list);
> +    NvdimmFitBuffer *fit_buf = &state->fit_buf;
>      unsigned int header;
>  
> +    /* NVDIMM device is not plugged? */
> +    if (!fit_buf->fit->len) {
it's not really obvious way to check for present nvdimms,
maybe dropping this hunk and keeping device_list check at call site would be clearer.

> +        return;
> +    }
> +
>      acpi_add_table(table_offsets, table_data);
>  
>      /* NFIT header. */
>      header = table_data->len;
>      acpi_data_push(table_data, sizeof(NvdimmNfitHeader));
>      /* NVDIMM device structures. */
> -    g_array_append_vals(table_data, structures->data, structures->len);
> +    g_array_append_vals(table_data, fit_buf->fit->data, fit_buf->fit->len);
>  
>      build_header(linker, table_data,
>                   (void *)(table_data->data + header), "NFIT",
> -                 sizeof(NvdimmNfitHeader) + structures->len, 1, NULL, NULL);
> -    g_array_free(structures, true);
> +                 sizeof(NvdimmNfitHeader) + fit_buf->fit->len, 1, NULL, NULL);
>  }
>  
>  struct NvdimmDsmIn {
> @@ -771,6 +790,8 @@ void nvdimm_init_acpi_state(AcpiNVDIMMState *state, MemoryRegion *io,
>      acpi_data_push(state->dsm_mem, sizeof(NvdimmDsmIn));
>      fw_cfg_add_file(fw_cfg, NVDIMM_DSM_MEM_FILE, state->dsm_mem->data,
>                      state->dsm_mem->len);
> +
> +    nvdimm_init_fit_buffer(&state->fit_buf);
>  }
>  
>  #define NVDIMM_COMMON_DSM       "NCAL"
> @@ -1045,25 +1066,17 @@ static void nvdimm_build_ssdt(GArray *table_offsets, GArray *table_data,
>  }
>  
>  void nvdimm_build_acpi(GArray *table_offsets, GArray *table_data,
> -                       BIOSLinker *linker, GArray *dsm_dma_arrea,
> +                       BIOSLinker *linker, AcpiNVDIMMState *state,
>                         uint32_t ram_slots)
>  {
> -    GSList *device_list;
> -
> -    device_list = nvdimm_get_plugged_device_list();
> -
> -    /* NVDIMM device is plugged. */
> -    if (device_list) {
> -        nvdimm_build_nfit(device_list, table_offsets, table_data, linker);
> -        g_slist_free(device_list);
> -    }
> +    nvdimm_build_nfit(state, table_offsets, table_data, linker);
>  
>      /*
>       * NVDIMM device is allowed to be plugged only if there is available
>       * slot.
>       */
>      if (ram_slots) {
> -        nvdimm_build_ssdt(table_offsets, table_data, linker, dsm_dma_arrea,
> +        nvdimm_build_ssdt(table_offsets, table_data, linker, state->dsm_mem,
>                            ram_slots);
you've ignored comments on v3 1/4,
fix it up.

>      }
>  }
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index 6ae4769..bc49958 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -2767,7 +2767,7 @@ void acpi_build(AcpiBuildTables *tables, MachineState *machine)
>      }
>      if (pcms->acpi_nvdimm_state.is_enabled) {
>          nvdimm_build_acpi(table_offsets, tables_blob, tables->linker,
> -                          pcms->acpi_nvdimm_state.dsm_mem, machine->ram_slots);
> +                          &pcms->acpi_nvdimm_state, machine->ram_slots);
>      }
>  
>      /* Add tables supplied by user (if any) */
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 93ff49c..77ca7f4 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1700,6 +1700,10 @@ static void pc_dimm_plug(HotplugHandler *hotplug_dev,
>          goto out;
>      }
>  
> +    if (object_dynamic_cast(OBJECT(dev), TYPE_NVDIMM)) {
> +        nvdimm_acpi_hotplug(&pcms->acpi_nvdimm_state);
s/nvdimm_acpi_hotplug/nvdimm_plug/

> +    }
> +
>      hhc = HOTPLUG_HANDLER_GET_CLASS(pcms->acpi_dev);
>      hhc->plug(HOTPLUG_HANDLER(pcms->acpi_dev), dev, &error_abort);
>  out:
> diff --git a/include/hw/mem/nvdimm.h b/include/hw/mem/nvdimm.h
> index 63a2b20..232437c 100644
> --- a/include/hw/mem/nvdimm.h
> +++ b/include/hw/mem/nvdimm.h
> @@ -98,12 +98,30 @@ typedef struct NVDIMMClass NVDIMMClass;
>  #define NVDIMM_ACPI_IO_BASE     0x0a18
>  #define NVDIMM_ACPI_IO_LEN      4
>  
> +/*
> + * The buffer, @fit, saves the FIT info for all the presented NVDIMM
> + * devices
FIT structures for present NVDIMMs

> + which is updated after the NVDIMM device is plugged or
> + * unplugged.
s/which is/. It is/
 
> + *
> + * Mark @dirty whenever the buffer is updated so that it preserves NVDIMM
> + * ACPI _FIT method to read incomplete or obsolete fit info if fit update
> + * happens during multiple RFIT calls.
> + */
not valid doc comment, see include/qom/object.h for example

> +struct NvdimmFitBuffer {
> +    GArray *fit;
> +    bool dirty;
> +};
> +typedef struct NvdimmFitBuffer NvdimmFitBuffer;
> +
>  struct AcpiNVDIMMState {
>      /* detect if NVDIMM support is enabled. */
>      bool is_enabled;
>  
>      /* the data of the fw_cfg file NVDIMM_DSM_MEM_FILE. */
>      GArray *dsm_mem;
> +
> +    NvdimmFitBuffer fit_buf;
> +
>      /* the IO region used by OSPM to transfer control to QEMU. */
>      MemoryRegion io_mr;
>  };
> @@ -112,6 +130,7 @@ typedef struct AcpiNVDIMMState AcpiNVDIMMState;
>  void nvdimm_init_acpi_state(AcpiNVDIMMState *state, MemoryRegion *io,
>                              FWCfgState *fw_cfg, Object *owner);
>  void nvdimm_build_acpi(GArray *table_offsets, GArray *table_data,
> -                       BIOSLinker *linker, GArray *dsm_dma_arrea,
> +                       BIOSLinker *linker, AcpiNVDIMMState *state,
>                         uint32_t ram_slots);
> +void nvdimm_acpi_hotplug(AcpiNVDIMMState *state);
>  #endif