On Sun, Jul 25, 2010 at 7:57 AM, Aurelien Jarno <aurel...@aurel32.net> wrote: > On Sun, Jul 25, 2010 at 01:58:51AM +0900, Jun Koi wrote: >> On Sat, Jul 24, 2010 at 11:49 AM, Aurelien Jarno <aurel...@aurel32.net> >> wrote: >> > On Sat, Jul 24, 2010 at 09:35:44AM +0900, Jun Koi wrote: >> >> On Sat, Jul 24, 2010 at 2:53 AM, Aurelien Jarno <aurel...@aurel32.net> >> >> wrote: >> >> > On Fri, Jul 23, 2010 at 08:59:54PM +0900, Jun Koi wrote: >> >> >> Hi, >> >> >> >> >> >> I am looking at the save_globals() of TCG code, and it seems this >> >> >> function saves regular registers like EAX, ..., EDI back to CPU state. >> >> >> >> >> >> But I am not sure if it also saves value of other registers, like >> >> >> EFlags, Segments, CR*, DR*, ... (?) >> >> >> From what I saw, it doesnt seem to do so. Is it correct? >> >> >> >> >> > >> >> > save_globals() is run before calling a function that can trigger a CPU >> >> > exception, to make sure that in that case all TCG variables are synced >> >> > with the CPU state. >> >> >> >> Is it correct? I always assume that save_globals() is also called at >> >> end of each block. >> > >> > Correct also here. >> > >> >> > >> >> > Given the CPU state only uses "normal" registers, there is no need to >> >> > save the other registers. >> >> >> >> Why do you say that CPU state includes only normal registers, given >> >> that, like on x86, CPUState has also segs[], cr[] and dr[]? >> >> >> >> >> >> >> >> Another question: if save_globals() only saves regular registers, >> >> where Qemu saves other registers like segs[], cr[]? Or do they always >> >> sync, all the time? >> > >> > It's actually the same question. You are mixing host and target >> > registers. save_globals() only saves "normal" host registers. Host >> > registers can then contain whatever registers from the target, and >> > more precisely the one declared as globals. >> > >> > >> >> Finally, how about Eflags? I remember that Eflags is "lazy sync", but >> >> does it sync at end of each block? >> >> >> > >> > It's the same. Eflags are actually stored in a lazy way in cc_* >> > globals. They are therefore synced with save_globals(). >> >> This is very helpful, thanks! >> >> Another question: as far as I can see in the code, most context is >> always synced, all the time. One exception is Eflags, which is only >> synced at the end of block. >> Is there other lazy synced context, besides EFLAGS? > > It depends on the target, some of ones are also syncing the program > counter lazily. >
ok, now i see that on x86, only EFLAGS is lazy sync. many thanks, J