Re: [PATCH v3 02/10] fw_cfg: Migrate ACPI table mr sizes separately

[Igor Mammedov]

On Wed, 11 Mar 2020 17:20:06 +0000
Shameer Kolothum <address@hidden> wrote:

> Any sub-page size update to ACPI table MRs will be lost during
> migration, as we use aligned size in ram_load_precopy() ->
> qemu_ram_resize() path. This will result in inconsistency in sizes
> between source and destination.
I'm not sure what problem is and if it matters in case of migration,
an example here with numbers from affected acpi blob would be useful here.

PS:
could you point to mail thread where problem was discussed

> In order to avoid this, save and
> restore them separately during migration.
> 
> Suggested-by: David Hildenbrand <address@hidden>
> Signed-off-by: Shameer Kolothum <address@hidden>
> ---
> Please find the discussion here,
> https://patchwork.kernel.org/patch/11339591/
> ---
>  hw/core/machine.c         |  1 +
>  hw/nvram/fw_cfg.c         | 86 ++++++++++++++++++++++++++++++++++++++-
>  include/hw/nvram/fw_cfg.h |  6 +++
>  3 files changed, 92 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 9e8c06036f..6d960bd47f 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -39,6 +39,7 @@ GlobalProperty hw_compat_4_2[] = {
>      { "usb-redir", "suppress-remote-wake", "off" },
>      { "qxl", "revision", "4" },
>      { "qxl-vga", "revision", "4" },
> +    { "fw_cfg", "acpi-mr-restore", "false" },
>  };
>  const size_t hw_compat_4_2_len = G_N_ELEMENTS(hw_compat_4_2);
>  
> diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
> index 179b302f01..36d1e32f83 100644
> --- a/hw/nvram/fw_cfg.c
> +++ b/hw/nvram/fw_cfg.c
> @@ -39,6 +39,7 @@
>  #include "qemu/config-file.h"
>  #include "qemu/cutils.h"
>  #include "qapi/error.h"
> +#include "hw/acpi/aml-build.h"
>  
>  #define FW_CFG_FILE_SLOTS_DFLT 0x20
>  
> @@ -610,6 +611,50 @@ bool fw_cfg_dma_enabled(void *opaque)
>      return s->dma_enabled;
>  }
>  
> +static bool fw_cfg_acpi_mr_restore(void *opaque)
> +{
> +    FWCfgState *s = opaque;
> +    return s->acpi_mr_restore;
> +}
> +
> +static void fw_cfg_update_mr(FWCfgState *s, uint16_t key, size_t size)
> +{
> +    MemoryRegion *mr;
> +    ram_addr_t offset;
> +    int arch = !!(key & FW_CFG_ARCH_LOCAL);
> +    void *ptr;
> +
> +    key &= FW_CFG_ENTRY_MASK;
> +    assert(key < fw_cfg_max_entry(s));
> +
> +    ptr = s->entries[arch][key].data;
> +    mr = memory_region_from_host(ptr, &offset);
> +
> +    memory_region_ram_resize(mr, size, &error_abort);
> +}
> +
> +static int fw_cfg_acpi_mr_restore_post_load(void *opaque, int version_id)
> +{
> +    FWCfgState *s = opaque;
> +    int i, index;
> +
> +    assert(s->files);
> +
> +    index = be32_to_cpu(s->files->count);
> +
> +    for (i = 0; i < index; i++) {
> +        if (!strcmp(s->files->f[i].name, ACPI_BUILD_TABLE_FILE)) {
> +            fw_cfg_update_mr(s, FW_CFG_FILE_FIRST + i, s->table_mr_size);
> +        } else if (!strcmp(s->files->f[i].name, ACPI_BUILD_LOADER_FILE)) {
> +            fw_cfg_update_mr(s, FW_CFG_FILE_FIRST + i, s->linker_mr_size);
> +        } else if (!strcmp(s->files->f[i].name, ACPI_BUILD_RSDP_FILE)) {
> +            fw_cfg_update_mr(s, FW_CFG_FILE_FIRST + i, s->rsdp_mr_size);
> +        }
> +    }
> +
> +    return 0;
> +}
> +
>  static const VMStateDescription vmstate_fw_cfg_dma = {
>      .name = "fw_cfg/dma",
>      .needed = fw_cfg_dma_enabled,
> @@ -619,6 +664,20 @@ static const VMStateDescription vmstate_fw_cfg_dma = {
>      },
>  };
>  
> +static const VMStateDescription vmstate_fw_cfg_acpi_mr = {
> +    .name = "fw_cfg/acpi_mr",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .needed = fw_cfg_acpi_mr_restore,
> +    .post_load = fw_cfg_acpi_mr_restore_post_load,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT64(table_mr_size, FWCfgState),
> +        VMSTATE_UINT64(linker_mr_size, FWCfgState),
> +        VMSTATE_UINT64(rsdp_mr_size, FWCfgState),
> +        VMSTATE_END_OF_LIST()
> +    },
> +};
> +
>  static const VMStateDescription vmstate_fw_cfg = {
>      .name = "fw_cfg",
>      .version_id = 2,
> @@ -631,6 +690,7 @@ static const VMStateDescription vmstate_fw_cfg = {
>      },
>      .subsections = (const VMStateDescription*[]) {
>          &vmstate_fw_cfg_dma,
> +        &vmstate_fw_cfg_acpi_mr,
>          NULL,
>      }
>  };
> @@ -815,6 +875,23 @@ static struct {
>  #define FW_CFG_ORDER_OVERRIDE_LAST 200
>  };
>  
> +/*
> + * Any sub-page size update to these table MRs will be lost during migration,
> + * as we use aligned size in ram_load_precopy() -> qemu_ram_resize() path.
> + * In order to avoid the inconsistency in sizes save them seperately and
> + * migrate over in vmstate post_load().
> + */
> +static void fw_cfg_acpi_mr_save(FWCfgState *s, const char *filename, size_t 
> len)
> +{
> +    if (!strcmp(filename, ACPI_BUILD_TABLE_FILE)) {
> +        s->table_mr_size = len;
> +    } else if (!strcmp(filename, ACPI_BUILD_LOADER_FILE)) {
> +        s->linker_mr_size = len;
> +    } else if (!strcmp(filename, ACPI_BUILD_RSDP_FILE)) {
> +        s->rsdp_mr_size = len;
> +    }
> +}
> +
>  static int get_fw_cfg_order(FWCfgState *s, const char *name)
>  {
>      int i;
> @@ -914,6 +991,7 @@ void fw_cfg_add_file_callback(FWCfgState *s,  const char 
> *filename,
>      trace_fw_cfg_add_file(s, index, s->files->f[index].name, len);
>  
>      s->files->count = cpu_to_be32(count+1);
> +    fw_cfg_acpi_mr_save(s, filename, len);
>  }
>  
>  void fw_cfg_add_file(FWCfgState *s,  const char *filename,
> @@ -937,6 +1015,7 @@ void *fw_cfg_modify_file(FWCfgState *s, const char 
> *filename,
>              ptr = fw_cfg_modify_bytes_read(s, FW_CFG_FILE_FIRST + i,
>                                             data, len);
>              s->files->f[i].size   = cpu_to_be32(len);
> +            fw_cfg_acpi_mr_save(s, filename, len);
>              return ptr;
>          }
>      }
> @@ -973,7 +1052,10 @@ static void fw_cfg_machine_ready(struct Notifier *n, 
> void *data)
>      qemu_register_reset(fw_cfg_machine_reset, s);
>  }
>  
> -
> +static Property fw_cfg_properties[] = {
> +    DEFINE_PROP_BOOL("acpi-mr-restore", FWCfgState, acpi_mr_restore, true),
> +    DEFINE_PROP_END_OF_LIST(),
> +};
>  
>  static void fw_cfg_common_realize(DeviceState *dev, Error **errp)
>  {
> @@ -1097,6 +1179,8 @@ static void fw_cfg_class_init(ObjectClass *klass, void 
> *data)
>  
>      dc->reset = fw_cfg_reset;
>      dc->vmsd = &vmstate_fw_cfg;
> +
> +    device_class_set_props(dc, fw_cfg_properties);
>  }
>  
>  static const TypeInfo fw_cfg_info = {
> diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h
> index b5291eefad..457fee7425 100644
> --- a/include/hw/nvram/fw_cfg.h
> +++ b/include/hw/nvram/fw_cfg.h
> @@ -53,6 +53,12 @@ struct FWCfgState {
>      dma_addr_t dma_addr;
>      AddressSpace *dma_as;
>      MemoryRegion dma_iomem;
> +
> +    /* restore during migration */
> +    bool acpi_mr_restore;
> +    size_t table_mr_size;
> +    size_t linker_mr_size;
> +    size_t rsdp_mr_size;
>  };
>  
>  struct FWCfgIoState {