Re: [PATCH v4 03/80] machine: alias -mem-path and -mem-prealloc into memory-foo backend

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Jan 31, 2020 at 04:08:33PM +0100, Igor Mammedov wrote:
> Allow machine to opt in for hostmem backend based initial RAM
> even if user uses old -mem-path/prealloc options by providing
>   MachineClass::default_ram_id
> Follow up patches will incrementally convert machines to new API,
> by dropping memory_region_allocate_system_memory() and setting
> default_ram_id that board used to use before conversion to keep
> migration stream the same.
> 
> Signed-off-by: Igor Mammedov <imammedo@redhat.com>

What about non-versioned machines though?
Why do these need to set default_ram_id?
Seems redundant as they don't need to support cross-version
migration ...


> ---
> v3:
>    * rename "ram-memdev" property to "memory-backend"
>      (Paolo Bonzini <pbonzini@redhat.com>)
> v4:
>    * previous patch changed memory-backend property from link
>      to string to allow for delayed backend creation, when
>      backend comes explicitly from CLI.
>      So s/object_property_set_link()/object_property_set_str()/
>      to account for that.
> 
> CC: ehabkost@redhat.com
> CC: pbonzini@redhat.com
> CC: philmd@redhat.com
> CC: pasic@linux.ibm.com
> ---
>  include/hw/boards.h      |  5 +++++
>  include/sysemu/hostmem.h | 16 ++++++++++++++++
>  backends/hostmem-file.c  |  7 -------
>  backends/hostmem-ram.c   |  2 --
>  vl.c                     | 25 +++++++++++++++++++++++++
>  5 files changed, 46 insertions(+), 9 deletions(-)
> 
> diff --git a/include/hw/boards.h b/include/hw/boards.h
> index 7b4b6b7..106de87 100644
> --- a/include/hw/boards.h
> +++ b/include/hw/boards.h
> @@ -170,6 +170,10 @@ typedef struct {
>   *    false is returned, an error must be set to show the reason of
>   *    the rejection.  If the hook is not provided, all hotplug will be
>   *    allowed.
> + * @default_ram_id:
> + *    Specifies inital RAM MemoryRegion name to be used for default backend
> + *    creation if user explicitly hasn't specified backend with "memory-backend"
> + *    property.
>   */
>  struct MachineClass {
>      /*< private >*/
> @@ -226,6 +230,7 @@ struct MachineClass {
>      bool nvdimm_supported;
>      bool numa_mem_supported;
>      bool auto_enable_numa;
> +    const char *default_ram_id;
>  
>      HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
>                                             DeviceState *dev);
> diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
> index 4dbdadd..5db0d66 100644
> --- a/include/sysemu/hostmem.h
> +++ b/include/sysemu/hostmem.h
> @@ -27,6 +27,22 @@
>  #define MEMORY_BACKEND_CLASS(klass) \
>      OBJECT_CLASS_CHECK(HostMemoryBackendClass, (klass), TYPE_MEMORY_BACKEND)
>  
> +/* hostmem-ram.c */
> +/**
> + * @TYPE_MEMORY_BACKEND_RAM:
> + * name of backend that uses mmap on the anonymous RAM
> + */
> +
> +#define TYPE_MEMORY_BACKEND_RAM "memory-backend-ram"
> +
> +/* hostmem-file.c */
> +/**
> + * @TYPE_MEMORY_BACKEND_FILE:
> + * name of backend that uses mmap on a file descriptor
> + */
> +#define TYPE_MEMORY_BACKEND_FILE "memory-backend-file"
> +
> +typedef struct HostMemoryBackend HostMemoryBackend;
>  typedef struct HostMemoryBackendClass HostMemoryBackendClass;
>  
>  /**
> diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
> index be64020..cb319a9 100644
> --- a/backends/hostmem-file.c
> +++ b/backends/hostmem-file.c
> @@ -18,13 +18,6 @@
>  #include "sysemu/sysemu.h"
>  #include "qom/object_interfaces.h"
>  
> -/* hostmem-file.c */
> -/**
> - * @TYPE_MEMORY_BACKEND_FILE:
> - * name of backend that uses mmap on a file descriptor
> - */
> -#define TYPE_MEMORY_BACKEND_FILE "memory-backend-file"
> -
>  #define MEMORY_BACKEND_FILE(obj) \
>      OBJECT_CHECK(HostMemoryBackendFile, (obj), TYPE_MEMORY_BACKEND_FILE)
>  
> diff --git a/backends/hostmem-ram.c b/backends/hostmem-ram.c
> index 6aab8d3..5cc53e7 100644
> --- a/backends/hostmem-ram.c
> +++ b/backends/hostmem-ram.c
> @@ -16,8 +16,6 @@
>  #include "qemu/module.h"
>  #include "qom/object_interfaces.h"
>  
> -#define TYPE_MEMORY_BACKEND_RAM "memory-backend-ram"
> -
>  static void
>  ram_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
>  {
> diff --git a/vl.c b/vl.c
> index 24951b5..2367cb6 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -75,6 +75,7 @@ int main(int argc, char **argv)
>  #include "ui/input.h"
>  #include "sysemu/sysemu.h"
>  #include "sysemu/numa.h"
> +#include "sysemu/hostmem.h"
>  #include "exec/gdbstub.h"
>  #include "qemu/timer.h"
>  #include "chardev/char.h"
> @@ -2839,6 +2840,26 @@ static void configure_accelerators(const char *progname)
>      }
>  }
>  
> +static void create_default_memdev(MachineState *ms, const char *path,
> +                                  bool prealloc)
> +{
> +    Object *obj;
> +    MachineClass *mc = MACHINE_GET_CLASS(ms);
> +
> +    obj = object_new(path ? TYPE_MEMORY_BACKEND_FILE : TYPE_MEMORY_BACKEND_RAM);
> +    if (path) {
> +        object_property_set_str(obj, path, "mem-path", &error_fatal);
> +    }
> +    object_property_set_bool(obj, prealloc, "prealloc", &error_fatal);
> +    object_property_set_int(obj, ms->ram_size, "size", &error_fatal);
> +    object_property_add_child(object_get_objects_root(), mc->default_ram_id,
> +                              obj, &error_fatal);
> +    user_creatable_complete(USER_CREATABLE(obj), &error_fatal);
> +    object_unref(obj);
> +    object_property_set_str(OBJECT(ms), mc->default_ram_id, "memory-backend",
> +                            &error_fatal);
> +}
> +
>  int main(int argc, char **argv, char **envp)
>  {
>      int i;
> @@ -4302,6 +4323,10 @@ int main(int argc, char **argv, char **envp)
>      }
>      parse_numa_opts(current_machine);
>  
> +    if (machine_class->default_ram_id && current_machine->ram_size &&
> +        !current_machine->ram_memdev_id) {
> +        create_default_memdev(current_machine, mem_path, mem_prealloc);
> +    }
>      /* do monitor/qmp handling at preconfig state if requested */
>      main_loop();

So this check for default_ram_id will become redundant after the
patchset is fully applied, this is just for bisect to work well, right?
I couldn't find patches that drop this check though.


> -- 
> 2.7.4
> 
>