Re: [PATCH v6 14/14] qmp/hmp, device_tree.c: introduce dumpdtb

[Dr. David Alan Gilbert]

* Daniel Henrique Barboza (danielhb413@gmail.com) wrote:
> To save the FDT blob we have the '-machine dumpdtb=<file>' property.
> With this property set, the machine saves the FDT in <file> and exit.
> The created file can then be converted to plain text dts format using
> 'dtc'.
> 
> There's nothing particularly sophisticated into saving the FDT that
> can't be done with the machine at any state, as long as the machine has
> a valid FDT to be saved.
> 
> The 'dumpdtb' command receives a 'filename' paramenter and, if a valid
> FDT is available, it'll save it in a file 'filename'. In short, this is
> a '-machine dumpdtb' that can be fired on demand via QMP/HMP.
> 
> A valid FDT consists of a FDT that was created using libfdt being
> retrieved via 'current_machine->fdt' in device_tree.c. This condition is
> met by most FDT users in QEMU.
> 
> This command will always be executed in-band (i.e. holding BQL),
> avoiding potential race conditions with machines that might change the
> FDT during runtime (e.g. PowerPC 'pseries' machine).
> 
> Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Cc: Markus Armbruster <armbru@redhat.com>
> Cc: Alistair Francis <alistair.francis@wdc.com>
> Cc: David Gibson <david@gibson.dropbear.id.au>
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>  hmp-commands.hx              | 15 +++++++++++++++
>  include/sysemu/device_tree.h |  1 +
>  monitor/misc.c               |  1 +
>  qapi/machine.json            | 18 ++++++++++++++++++
>  softmmu/device_tree.c        | 31 +++++++++++++++++++++++++++++++
>  5 files changed, 66 insertions(+)
> 
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index 182e639d14..9a3e57504f 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -1800,3 +1800,18 @@ ERST
>                        "\n\t\t\t\t\t limit on a specified virtual cpu",
>          .cmd        = hmp_cancel_vcpu_dirty_limit,
>      },
> +
> +#if defined(CONFIG_FDT)
> +SRST
> +``dumpdtb`` *filename*
> +  Save the FDT in the 'filename' file to be decoded using dtc.
> +  Requires 'libfdt' support.
> +ERST

Can you please put the SRST/ERST below the { }'s please;  most of the
hmp-commands.hx has it that way around but it looks like the diry
rate/limit set at the bottom have them flipped which we need to fix.

> +    {
> +        .name       = "dumpdtb",
> +        .args_type  = "filename:F",
> +        .params     = "filename",
> +        .help       = "save the FDT in the 'filename' file to be decoded 
> using dtc",
> +        .cmd        = hmp_dumpdtb,
> +    },
> +#endif

Other than the flip,

Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h
> index ef060a9759..e7c5441f56 100644
> --- a/include/sysemu/device_tree.h
> +++ b/include/sysemu/device_tree.h
> @@ -136,6 +136,7 @@ int qemu_fdt_add_path(void *fdt, const char *path);
>      } while (0)
>  
>  void qemu_fdt_dumpdtb(void *fdt, int size);
> +void hmp_dumpdtb(Monitor *mon, const QDict *qdict);
>  
>  /**
>   * qemu_fdt_setprop_sized_cells_from_array:
> diff --git a/monitor/misc.c b/monitor/misc.c
> index 3d2312ba8d..e7dd63030b 100644
> --- a/monitor/misc.c
> +++ b/monitor/misc.c
> @@ -49,6 +49,7 @@
>  #include "sysemu/blockdev.h"
>  #include "sysemu/sysemu.h"
>  #include "sysemu/tpm.h"
> +#include "sysemu/device_tree.h"
>  #include "qapi/qmp/qdict.h"
>  #include "qapi/qmp/qerror.h"
>  #include "qapi/qmp/qstring.h"
> diff --git a/qapi/machine.json b/qapi/machine.json
> index 6afd1936b0..f968a5d343 100644
> --- a/qapi/machine.json
> +++ b/qapi/machine.json
> @@ -1664,3 +1664,21 @@
>       '*size': 'size',
>       '*max-size': 'size',
>       '*slots': 'uint64' } }
> +
> +##
> +# @dumpdtb:
> +#
> +# Save the FDT in dtb format. Requires 'libfdt' support.
> +#
> +# @filename: name of the FDT file to be created
> +#
> +# Since: 7.2
> +#
> +# Example:
> +#   {"execute": "dumpdtb"}
> +#    "arguments": { "filename": "/tmp/fdt.dtb" } }
> +#
> +##
> +{ 'command': 'dumpdtb',
> +  'data': { 'filename': 'str' },
> +  'if': 'CONFIG_FDT' }
> diff --git a/softmmu/device_tree.c b/softmmu/device_tree.c
> index 6ca3fad285..cdd41b6de6 100644
> --- a/softmmu/device_tree.c
> +++ b/softmmu/device_tree.c
> @@ -26,6 +26,9 @@
>  #include "hw/loader.h"
>  #include "hw/boards.h"
>  #include "qemu/config-file.h"
> +#include "qapi/qapi-commands-machine.h"
> +#include "qapi/qmp/qdict.h"
> +#include "monitor/hmp.h"
>  
>  #include <libfdt.h>
>  
> @@ -643,3 +646,31 @@ out:
>      g_free(propcells);
>      return ret;
>  }
> +
> +void qmp_dumpdtb(const char *filename, Error **errp)
> +{
> +    g_autoptr(GError) err = NULL;
> +    int size;
> +
> +    if (!current_machine->fdt) {
> +        error_setg(errp, "Unable to find the machine FDT");
> +        return;
> +    }
> +
> +    size = fdt_totalsize(current_machine->fdt);
> +
> +    if (!g_file_set_contents(filename, current_machine->fdt, size, &err)) {
> +        error_setg(errp, "Error saving FDT to file %s: %s",
> +                   filename, err->message);
> +    }
> +}
> +
> +void hmp_dumpdtb(Monitor *mon, const QDict *qdict)
> +{
> +    const char *filename = qdict_get_str(qdict, "filename");
> +    Error *local_err = NULL;
> +
> +    qmp_dumpdtb(filename, &local_err);
> +
> +    hmp_handle_error(mon, local_err);
> +}
> -- 
> 2.37.2
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK