On Mon, May 24, 2010 at 6:03 PM, Anthony Liguori <anth...@codemonkey.ws> wrote: > On 05/24/2010 12:54 PM, Juan Quintela wrote: >> >> Paul Brook<p...@codesourcery.com> wrote: >> >>>> >>>> On 05/24/2010 11:32 AM, Paul Brook wrote: >>>> >>>>>> >>>>>> Notice that this patch was sent against hpet as one example, if we >>>>>> agree >>>>>> that this "way" of disabling devices is ok, we could disable more >>>>>> devices/have more flexibility. Notice that in general, we (RHEL/KVM) >>>>>> are interested in a small subset of qemu devices. >>>>>> >>>>> >>>>> IMO this patch is a backwards step. The device models should be >>>>> cleaned >>>>> up so that you don't need to make a compile time decision. >>>>> >>>> >>>> I disagree. I think the device model should be cleaned up so that no >>>> CONFIG_HPET is required in code but I think it's still useful to be able >>>> to exclude device models from the build. That should just be a matter >>>> of not building the object though (that's the point of device_init()). >>>> >>> >>> I think we're saying the same thing. >>> >>> We already have a mechanism for avoiding things at build time - >>> specifically >>> config-devices.mak. We don't have a nice UI for it, but it's there. >>> At worst your distro specific patch is a 1-line change to default- >>> configs/i386-softmmu.mak. >>> >>> I have no objection to moving hpet.c into Makefile.objs, conditional on >>> CONFIG_HPET (like e.g. CONFIG_SERIAL/serial.o). However a necessary >>> prerequisite is that you fix the device model and machine initialisation >>> so >>> that it's possible to omit hpet.o without rebuilding anything else. >>> >> >> We have two exported functions: >> >> void hpet_init(qemu_irq *irq); >> uint32_t hpet_in_legacy_mode(void); >> >> This is how one is used in mc14818rtc: >> >> #if defined TARGET_I386 >> if (!hpet_in_legacy_mode()) >> #endif >> > > In real hardware, and HPET would normally emulate an RTC. The interaction > problem here is that we aren't modelling that correctly in qemu as we're > treating the rtc as a separate device. > > What could probably work at a hand wave level, is to make the rtc init > function take a qemu_irq instead of directly grabbing the isa irq. When an > HPET is in use, the rtc no longer is directly initiated but instead is > indirectly initiated by the HPET passing a special qemu_irq to the device > that masks the actual interrupt line when legacy mode isn't enabled. When > the HPET isn't in use, the rtc would be created with an isa allocated > qemu_irq.
Fully agree, HPET logic should be moved into HPET. I think my yesterday's patches only went half way.
