On Thu, Oct 27, 2016 at 12:23:00PM +0800, Haozhong Zhang wrote:
> If 'size' option is not given, Qemu will use the file size of 'mem-path'
> instead. If an empty file, a non-existing file or a directory is specified
> by option 'mem-path', a non-zero option 'size' is still needed.
>
> Signed-off-by: Haozhong Zhang <haozhong.zh...@intel.com>
> ---
> backends/hostmem-file.c | 28 ++++++++++++++++++++--------
> exec.c | 33 ++++++++++++++++++++-------------
> 2 files changed, 40 insertions(+), 21 deletions(-)
>
> diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
> index 42efb2f..6ee4352 100644
> --- a/backends/hostmem-file.c
> +++ b/backends/hostmem-file.c
> @@ -39,17 +39,14 @@ static void
> file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
> {
> HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(backend);
> + Error *local_err = NULL;
>
> - 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;
> + error_setg(&local_err, "mem-path property not set");
> + goto out;
> }
> #ifndef CONFIG_LINUX
> - error_setg(errp, "-mem-path not supported on this host");
> + error_setg(&local_err, "-mem-path not supported on this host");
> #else
> if (!memory_region_size(&backend->mr)) {
> gchar *path;
> @@ -58,10 +55,25 @@ file_backend_memory_alloc(HostMemoryBackend *backend,
> Error **errp)
> memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
> path,
> backend->size, fb->share,
> - fb->mem_path, errp);
> + fb->mem_path, &local_err);
> g_free(path);
> +
> + if (local_err) {
> + goto out;
> + }
> +
> + if (!backend->size) {
> + backend->size = memory_region_size(&backend->mr);
> + }
> }
> #endif
> +
> + if (!backend->size) {
> + error_setg(&local_err, "can't create backend with size 0");
> + }
You need to move this check before the #endif line, as an error
is already unconditionally set in local_err in the !CONFIG_LINUX
path, and a second error_setg() call would trigger an assert()
inside error_setv().
> +
> + out:
> + error_propagate(errp, local_err);
> }
>
> static char *get_mem_path(Object *o, Error **errp)
> diff --git a/exec.c b/exec.c
> index 264a25f..89065bd 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1234,7 +1234,7 @@ static int64_t get_file_size(int fd)
> }
>
> static void *file_ram_alloc(RAMBlock *block,
> - ram_addr_t memory,
> + ram_addr_t *memory,
> const char *path,
> Error **errp)
> {
> @@ -1245,6 +1245,7 @@ static void *file_ram_alloc(RAMBlock *block,
> void *area = MAP_FAILED;
> int fd = -1;
> int64_t file_size;
> + ram_addr_t mem_size = *memory;
>
> if (kvm_enabled() && !kvm_has_sync_mmu()) {
> error_setg(errp,
> @@ -1309,21 +1310,27 @@ static void *file_ram_alloc(RAMBlock *block,
>
> file_size = get_file_size(fd);
>
> - if (memory < block->page_size) {
> + if (!mem_size && file_size > 0) {
> + mem_size = file_size;
Maybe we should set *memory here and not below?
> + memory_region_set_size(block->mr, mem_size);
This could be simplified (and made safer) if the memory region
got initialized by memory_region_init_ram_from_file() after we
already mapped/allocated the file (so we avoid surprises in case
other code does something weird because of the temporarily
zero-sized MemoryRegion). But it would probably be an intrusive
change, so I guess changing the memory size here is OK. Paolo,
what do you think?
> + }
> +
> + if (mem_size < block->page_size) {
> error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to "
> "or larger than page size 0x%zx",
> - memory, block->page_size);
> + mem_size, block->page_size);
> goto error;
> }
>
> - if (file_size > 0 && file_size < memory) {
> + if (file_size > 0 && file_size < mem_size) {
> error_setg(errp, "backing store %s size %"PRId64
> " does not match 'size' option %"PRIu64,
> - path, file_size, memory);
> + path, file_size, mem_size);
> goto error;
> }
>
> - memory = ROUND_UP(memory, block->page_size);
> + mem_size = ROUND_UP(mem_size, block->page_size);
> + *memory = mem_size;
Why exactly did you choose to set *memory to the rounded-up size
and not file_size? Changing *memory to the rounded-up value would
be additional behavior that is not described in the commit
message. I believe we should change *memory only if *memory == 0,
and avoid touching it otherwise.
>
> /*
> * ftruncate is not supported by hugetlbfs in older
> @@ -1339,11 +1346,11 @@ static void *file_ram_alloc(RAMBlock *block,
> * those labels. Therefore, extending the non-empty backend file
> * is disabled as well.
> */
> - if (!file_size && ftruncate(fd, memory)) {
> + if (!file_size && ftruncate(fd, mem_size)) {
> perror("ftruncate");
> }
>
> - area = qemu_ram_mmap(fd, memory, block->mr->align,
> + area = qemu_ram_mmap(fd, mem_size, block->mr->align,
> block->flags & RAM_SHARED);
> if (area == MAP_FAILED) {
> error_setg_errno(errp, errno,
> @@ -1352,7 +1359,7 @@ static void *file_ram_alloc(RAMBlock *block,
> }
>
> if (mem_prealloc) {
> - os_mem_prealloc(fd, area, memory, errp);
> + os_mem_prealloc(fd, area, mem_size, errp);
> if (errp && *errp) {
> goto error;
> }
> @@ -1363,7 +1370,7 @@ static void *file_ram_alloc(RAMBlock *block,
>
> error:
> if (area != MAP_FAILED) {
> - qemu_ram_munmap(area, memory);
> + qemu_ram_munmap(area, mem_size);
> }
> if (unlink_on_error) {
> unlink(path);
> @@ -1690,15 +1697,15 @@ RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size,
> MemoryRegion *mr,
> size = HOST_PAGE_ALIGN(size);
> new_block = g_malloc0(sizeof(*new_block));
> new_block->mr = mr;
> - new_block->used_length = size;
> - new_block->max_length = size;
> new_block->flags = share ? RAM_SHARED : 0;
> - new_block->host = file_ram_alloc(new_block, size,
> + new_block->host = file_ram_alloc(new_block, &size,
> mem_path, errp);
> if (!new_block->host) {
> g_free(new_block);
> return NULL;
> }
> + new_block->used_length = size;
> + new_block->max_length = size;
>
> ram_block_add(new_block, &local_err);
> if (local_err) {
> --
> 2.10.1
>
--
Eduardo
