On Wed, 1 Aug 2012, Konrad Rzeszutek Wilk wrote:
+struct pvclock_wall_clock {
- u32 version;
- u32 sec;
- u32 nsec;
+} __attribute__((__packed__));
That is weird. It is 4+4+4 = 12 bytes? Don't you want it to be 16 bytes?
I agree that 16 bytes would be a better choice, but it needs to match the struct in Xen that is defined as follow:
uint32_t wc_version; /* Version counter: see vcpu_time_info_t. */ uint32_t wc_sec; /* Secs 00:00:00 UTC, Jan 1, 1970. */ uint32_t wc_nsec; /* Nsecs 00:00:00 UTC, Jan 1, 1970. */Would it make sense to add some paddigin then at least? In both cases? Or is it too late for this?
I can see why adding some padding would be useful if the structs were not packed and we wanted to enforce 32/64 bit compatibility on x86. However on ARM the field alignments on 32 and 64 bits are the same for integer values so the padding wouldn't make a difference. In any case both structs are packed, so the alignment is forced to be the same by the compiler.