Peter Xu <pet...@redhat.com> writes: > On Mon, Dec 04, 2023 at 06:09:16PM -0300, Fabiano Rosas wrote: >> Right, I got your point. I just think we could avoid designing this new >> string format by creating new fields with the extra space: >> >> typedef struct QEMU_PACKED { >> uint32_t size; >> uint8_t runstate[50]; >> uint8_t unused[50]; >> RunState state; >> bool received; >> } GlobalState; >> >> In my mind this works seamlessly, or am I mistaken? > > I think what you proposed should indeed work. > > Currently it's: > > .fields = (VMStateField[]) { > VMSTATE_UINT32(size, GlobalState), > VMSTATE_BUFFER(runstate, GlobalState), > VMSTATE_END_OF_LIST() > }, > > I had a quick look at vmstate_info_buffer, it mostly only get()/put() those > buffers with its sizeof(), so looks all fine. For sure in all cases we'd > better test it to verify. > > One side note is since we so far use qapi_enum_parse() for the runstate, I > think the "size" is not ever used.. > > If we do want a split, IMHO we can consider making runstate[] even smaller > to just free up the rest spaces all in one shot: > > typedef struct QEMU_PACKED { > uint32_t size; > /* > * Assuming 16 is good enough to fit all possible runstate strings.. > * This field must be a string ending with '\0'. > */ > uint8_t runstate[16]; > /* 0x00 when QEMU doesn't support it, or "0"/"1" to reflect its state */ > uint8_t vm_was_suspended[1]; > /* > * Still free of use space. Note that we only have 99 bytes for use > * because the last byte (the 100th byte) must be zero due to legacy > * reasons, if not it may be set to zero after loaded on dest QEMU. > */
I'd add a 'uint8_t reserved;' to go along with this comment instead of leaving a hole.