[PATCHv2,for-2.13,2/2] Add host_memory_backend_pagesize() helper

There are a couple places (one generic, one target specific) where we need
to get the host page size associated with a particular memory backend.  I
have some upcoming code which will add another place which wants this.  So,
for convenience, add a helper function to calculate this.

host_memory_backend_pagesize() returns the host pagesize for a given
HostMemoryBackend object.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 backends/hostmem.c       | 11 +++++++++++
 exec.c                   |  5 ++---
 include/sysemu/hostmem.h |  2 ++
 target/ppc/kvm.c         |  6 +-----
 4 files changed, 16 insertions(+), 8 deletions(-)

On Thu,  5 Apr 2018 12:20:02 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> There are a couple places (one generic, one target specific) where we need
> to get the host page size associated with a particular memory backend.  I
> have some upcoming code which will add another place which wants this.  So,
> for convenience, add a helper function to calculate this.
> 
> host_memory_backend_pagesize() returns the host pagesize for a given
> HostMemoryBackend object.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---

Reviewed-by: Greg Kurz <groug@kaod.org>

>  backends/hostmem.c       | 11 +++++++++++
>  exec.c                   |  5 ++---
>  include/sysemu/hostmem.h |  2 ++
>  target/ppc/kvm.c         |  6 +-----
>  4 files changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/backends/hostmem.c b/backends/hostmem.c
> index f61093654e..ff2bb0489c 100644
> --- a/backends/hostmem.c
> +++ b/backends/hostmem.c
> @@ -18,6 +18,7 @@
>  #include "qapi/visitor.h"
>  #include "qemu/config-file.h"
>  #include "qom/object_interfaces.h"
> +#include "qemu/mmap-alloc.h"
>  
>  #ifdef CONFIG_NUMA
>  #include <numaif.h>
> @@ -262,6 +263,16 @@ bool host_memory_backend_is_mapped(HostMemoryBackend *backend)
>      return backend->is_mapped;
>  }
>  
> +size_t host_memory_backend_pagesize(HostMemoryBackend *memdev)
> +{
> +    Object *obj = OBJECT(memdev);
> +    char *path = object_property_get_str(obj, "mem-path", NULL);
> +    size_t pagesize = qemu_mempath_getpagesize(path);
> +
> +    g_free(path);
> +    return pagesize;
> +}
> +
>  static void
>  host_memory_backend_memory_complete(UserCreatable *uc, Error **errp)
>  {
> diff --git a/exec.c b/exec.c
> index b38b004563..c7fcefa851 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1491,9 +1491,8 @@ static int find_max_supported_pagesize(Object *obj, void *opaque)
>      long *hpsize_min = opaque;
>  
>      if (object_dynamic_cast(obj, TYPE_MEMORY_BACKEND)) {
> -        char *mem_path = object_property_get_str(obj, "mem-path", NULL);
> -        long hpsize = qemu_mempath_getpagesize(mem_path);
> -        g_free(mem_path);
> +        long hpsize = host_memory_backend_pagesize(MEMORY_BACKEND(obj));
> +
>          if (hpsize < *hpsize_min) {
>              *hpsize_min = hpsize;
>          }
> diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
> index 47bc9846ac..bc36899bb8 100644
> --- a/include/sysemu/hostmem.h
> +++ b/include/sysemu/hostmem.h
> @@ -68,4 +68,6 @@ MemoryRegion *host_memory_backend_get_memory(HostMemoryBackend *backend,
>  
>  void host_memory_backend_set_mapped(HostMemoryBackend *backend, bool mapped);
>  bool host_memory_backend_is_mapped(HostMemoryBackend *backend);
> +size_t host_memory_backend_pagesize(HostMemoryBackend *memdev);
> +
>  #endif
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index f393eae127..1ab9cf3a8a 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -493,11 +493,7 @@ static void kvm_fixup_page_sizes(PowerPCCPU *cpu)
>  bool kvmppc_is_mem_backend_page_size_ok(const char *obj_path)
>  {
>      Object *mem_obj = object_resolve_path(obj_path, NULL);
> -    char *mempath = object_property_get_str(mem_obj, "mem-path", NULL);
> -    long pagesize;
> -
> -    pagesize = qemu_mempath_getpagesize(mempath);
> -    g_free(mempath);
> +    long pagesize = host_memory_backend_pagesize(MEMORY_BACKEND(mem_obj));
>  
>      return pagesize >= max_cpu_page_size;
>  }