Re: [Qemu-devel] [PATCH v4 18/29] hostmem: add file-based HostMemoryBackend

[Michael S. Tsirkin]

On Mon, Jun 09, 2014 at 01:32:46PM +0200, Igor Mammedov wrote:
> On Mon, 9 Jun 2014 18:25:23 +0800
> Hu Tao <address@hidden> wrote:
> 
> > From: Paolo Bonzini <address@hidden>
> > 
> > Signed-off-by: Paolo Bonzini <address@hidden>
> > Signed-off-by: Hu Tao <address@hidden>
> > ---
> >  backends/Makefile.objs  |   1 +
> >  backends/hostmem-file.c | 107 
> > ++++++++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 108 insertions(+)
> >  create mode 100644 backends/hostmem-file.c
> > 
> > diff --git a/backends/Makefile.objs b/backends/Makefile.objs
> > index 7fb7acd..506a46c 100644
> > --- a/backends/Makefile.objs
> > +++ b/backends/Makefile.objs
> > @@ -8,3 +8,4 @@ baum.o-cflags := $(SDL_CFLAGS)
> >  common-obj-$(CONFIG_TPM) += tpm.o
> >  
> >  common-obj-y += hostmem.o hostmem-ram.o
> > +common-obj-$(CONFIG_LINUX) += hostmem-file.o
> > diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
> > new file mode 100644
> > index 0000000..b8df933
> > --- /dev/null
> > +++ b/backends/hostmem-file.c
> > @@ -0,0 +1,107 @@
> > +/*
> > + * QEMU Host Memory Backend for hugetlbfs
> > + *
> > + * Copyright (C) 2013 Red Hat Inc
> > + *
> > + * Authors:
> > + *   Paolo Bonzini <address@hidden>
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or 
> > later.
> > + * See the COPYING file in the top-level directory.
> > + */
> > +#include "sysemu/hostmem.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"
> how about naming it after what it really is? "memory-backend-hugepage"
> Later we could split it into generic superclass mmap-ed "memory-backend-file"
> and have TPH specific code moved into this backend.

What does this last sentence mean?

THP is transparent huge pages, right?



> > +
> > +#define MEMORY_BACKEND_FILE(obj) \
> > +    OBJECT_CHECK(HostMemoryBackendFile, (obj), TYPE_MEMORY_BACKEND_FILE)
> > +
> > +typedef struct HostMemoryBackendFile HostMemoryBackendFile;
> > +
> > +struct HostMemoryBackendFile {
> > +    HostMemoryBackend parent_obj;
> > +    char *mem_path;
> > +};
> > +
> > +static void
> > +file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
> > +{
> > +    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(backend);
> > +
> > +    if (!backend->size) {
> > +        error_setg(errp, "can't create backend with size 0");
> > +        return;
> > +    }
> > +    if (!fb->mem_path) {
> > +        error_setg(errp, "mem-path property not set");
> > +        return;
> > +    }
> > +#ifndef CONFIG_LINUX
> > +    error_setg(errp, "-mem-path not supported on this host");
> Is it possible to not compile this backend on non linux host at all, instead
> of ifdefs.
> 
> > +#else
> > +    if (!memory_region_size(&backend->mr)) {
> > +        memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
> > +                                 
> > object_get_canonical_path(OBJECT(backend)),
> > +                                 backend->size,
> > +                                 fb->mem_path, errp);
> > +    }
> > +#endif
> > +}
> > +
> > +static void
> > +file_backend_class_init(ObjectClass *oc, void *data)
> > +{
> > +    HostMemoryBackendClass *bc = MEMORY_BACKEND_CLASS(oc);
> > +
> > +    bc->alloc = file_backend_memory_alloc;
> > +}
> > +
> > +static char *get_mem_path(Object *o, Error **errp)
> > +{
> > +    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
> > +
> > +    return g_strdup(fb->mem_path);
> > +}
> > +
> > +static void set_mem_path(Object *o, const char *str, Error **errp)
> > +{
> > +    HostMemoryBackend *backend = MEMORY_BACKEND(o);
> > +    HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
> > +
> > +    if (memory_region_size(&backend->mr)) {
> > +        error_setg(errp, "cannot change property value");
> > +        return;
> > +    }
> > +    if (fb->mem_path) {
> > +        g_free(fb->mem_path);
> > +    }
> > +    fb->mem_path = g_strdup(str);
> > +}
> > +
> > +static void
> > +file_backend_instance_init(Object *o)
> > +{
> > +    object_property_add_str(o, "mem-path", get_mem_path,
> > +                            set_mem_path, NULL);
> s/"mem-path"/"path"/
> 
> 
> > +}
> > +
> > +static const TypeInfo file_backend_info = {
> > +    .name = TYPE_MEMORY_BACKEND_FILE,
> > +    .parent = TYPE_MEMORY_BACKEND,
> > +    .class_init = file_backend_class_init,
> > +    .instance_init = file_backend_instance_init,
> > +    .instance_size = sizeof(HostMemoryBackendFile),
> > +};
> > +
> > +static void register_types(void)
> > +{
> > +    type_register_static(&file_backend_info);
> > +}
> > +
> > +type_init(register_types);
> > -- 
> > 1.9.3
> > 
> 
> 
> -- 
> Regards,
>   Igor