2009/12/20 Gleb Natapov <g...@redhat.com>: > On Sun, Dec 20, 2009 at 04:08:32PM +0000, Blue Swirl wrote: >> On Sun, Dec 20, 2009 at 3:52 PM, Gleb Natapov <g...@redhat.com> wrote: >> > On Sun, Dec 20, 2009 at 09:39:38AM -0600, Anthony Liguori wrote: >> >> Gleb Natapov wrote: >> >> >>More importantly though, what's the use-case here? >> >> >> >> >> >Use-case for what? This just what need to be done for correct HW >> >> >emulation. >> >> >> >> Live migration is transparent to the guest. The fact that firmware >> >> can upgrade itself without the guest doing anything is not something >> >> that really has a real world equivalent. >> >> >> >> Even if it did, whether that automatic upgrade happens after a >> >> reboot vs. a hard power cycle is irrelevant. The guest has no >> >> knowledge of the fact that the automatic firmware upgrade happened >> >> so if it gets delayed indefinitely, it doesn't matter. >> >> >> >> It's not a matter of correctness IMHO. >> >> >> > Ah now I see what you mean. New FW has to be used after reboot because old >> > one may not be able to init HW any longer. Suppose some bug in cirrus >> > emulation has being fixed and old vga bios should be accommodated to >> > those changes, if old vga bios will run after reset video output may not >> > work. Thinking about it we'll have the same problem if migration happens >> > during vga bios loading, but this is MUCH less likely to happen. >> > >> >> I can understand an argument for predictability wrt wanted to be >> >> able to guarantee that after the first reboot during a live >> >> migration, you'll get the new firmware. I'm not sure that's less >> >> predictable then hard shutdown/start-up and I'm not sure I can >> >> really make an argument for one way vs. the other. >> >> >> > system_reset _is_ hard shutdown/start-up. If it is not it is a bug, we >> > just arguing if the same applies for the case that migration was done >> > between boot and reset. >> >> Some devices are careful enough to implement warm reset using a flag, >> see for example hw/sun4u.c. If you want more precision, you could >> introduce for example system_off_on with the memory clearing behavior >> you want. > I am not familiar with other architectures. All I am saying applies to > IBM PC only. Of course it is possible to design a system that impossible > to reset completely from software or by pushing reset button. (To design > general purpose computer like that one should be braindead though). On > IBM PC there are ways to reset different parts of the system and there > are ways to completely reset the system. We support only the later and > ACPI spec mandates this kind of reset if reset is done via ACPI.
Then hw/pc.c could install a reset handler that clears all memory etc.
