Re: [PATCH v2 1/3] backends/hostmem: Fix support of memory-backend-memfd in qemu_maxrampagesize()

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Wed, 10 Aug 2022 14:57:18 +0200
Thomas Huth <thuth@redhat.com> wrote:

> It is currently not possible yet to use "memory-backend-memfd" on s390x
> with hugepages enabled. This problem is caused by qemu_maxrampagesize()
> not taking memory-backend-memfd objects into account yet, so the code
> in s390_memory_init() fails to enable the huge page support there via
> s390_set_max_pagesize(). Fix it by generalizing the code, so that it
> looks at qemu_ram_pagesize(memdev->mr.ram_block) instead of re-trying
> to get the information from the filesystem.
> 
> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2116496
> Suggested-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>

more removed lines than added, I like it

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  backends/hostmem.c | 14 ++------------
>  1 file changed, 2 insertions(+), 12 deletions(-)
> 
> diff --git a/backends/hostmem.c b/backends/hostmem.c
> index 624bb7ecd3..4428e06738 100644
> --- a/backends/hostmem.c
> +++ b/backends/hostmem.c
> @@ -306,22 +306,12 @@ bool host_memory_backend_is_mapped(HostMemoryBackend *backend)
>      return backend->is_mapped;
>  }
>  
> -#ifdef __linux__
>  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);
> +    size_t pagesize = qemu_ram_pagesize(memdev->mr.ram_block);
> +    g_assert(pagesize >= qemu_real_host_page_size());
>      return pagesize;
>  }
> -#else
> -size_t host_memory_backend_pagesize(HostMemoryBackend *memdev)
> -{
> -    return qemu_real_host_page_size();
> -}
> -#endif
>  
>  static void
>  host_memory_backend_memory_complete(UserCreatable *uc, Error **errp)