Re: [PATCH 2/2] Add -mem-shared option

[Eduardo Habkost]

+Igor

On Thu, Nov 28, 2019 at 06:15:18PM +0400, Marc-André Lureau wrote:
> Add an option to simplify shared memory / vhost-user setup.
> 
> Currently, using vhost-user requires NUMA setup such as:
> -m 4G -object memory-backend-file,id=mem,size=4G,mem-path=/dev/shm,share=on 
> -numa node,memdev=mem
> 
> As there is no other way to allocate shareable RAM, afaik.
> 
> -mem-shared aims to have a simple way instead: -m 4G -mem-shared
> 
> Signed-off-by: Marc-André Lureau <address@hidden>
> ---
[...]
> diff --git a/hw/core/numa.c b/hw/core/numa.c
> index e3332a984f..6f72cddb1c 100644
> --- a/hw/core/numa.c
> +++ b/hw/core/numa.c
> @@ -493,7 +493,8 @@ static void allocate_system_memory_nonnuma(MemoryRegion 
> *mr, Object *owner,
>      if (mem_path) {
>  #ifdef __linux__
>          Error *err = NULL;
> -        memory_region_init_ram_from_file(mr, owner, name, ram_size, 0, 0,
> +        memory_region_init_ram_from_file(mr, owner, name, ram_size, 0,
> +                                         mem_shared ? RAM_SHARED : 0,
>                                           mem_path, &err);
>          if (err) {
>              error_report_err(err);
> @@ -513,6 +514,19 @@ static void allocate_system_memory_nonnuma(MemoryRegion 
> *mr, Object *owner,
>  #else
>          fprintf(stderr, "-mem-path not supported on this host\n");
>          exit(1);
> +#endif
> +    } else if (mem_shared) {
> +#ifdef CONFIG_POSIX
> +        Error *err = NULL;
> +        memory_region_init_ram_from_file(mr, owner, NULL, ram_size, 0,
> +                                         RAM_SHARED, NULL, &err);
> +        if (err) {
> +            error_report_err(err);
> +            exit(1);
> +        }
> +#else
> +        fprintf(stderr, "-mem-shared not supported on this host\n");
> +        exit(1);
>  #endif
>      } else {
>          memory_region_init_ram_nomigrate(mr, owner, name, ram_size, 
> &error_fatal);

I'd really like make allocate_system_memory_nonnuma() just create
a memory backend object.  This way non-NUMA and NUMA
configuration would be able to use exactly the same set of
options.

I have the impression we tried to do this in the past.  Igor, do
you remember if we did?

-- 
Eduardo