On Sun, Sep 29, 2013 at 12:20 PM, Michael S. Tsirkin <m...@redhat.com> wrote: > On Sun, Sep 29, 2013 at 11:25:24AM +0800, liu ping fan wrote: >> On Sun, Sep 29, 2013 at 3:52 AM, Michael S. Tsirkin <m...@redhat.com> wrote: >> > On Thu, Sep 12, 2013 at 11:25:14AM +0800, Liu Ping Fan wrote: >> >> According to hpet spec, hpet irq is high active. But according to >> >> ICH spec, there is inversion before the input of ioapic. So the OS >> >> will expect low active on this IRQ line. >> > >> > >> >>(And this is observed on >> >> bare metal). >> > >> > How does one test this on bare metal? >> > >> If changing the func hpet_timer_set_irq() in linux's hpet driver, >> from acpi_register_gsi(NULL, irq, ACPI_LEVEL_SENSITIVE, >> ACPI_ACTIVE_LOW); to ACPI_ACTIVE_HIGH, then run hpet_example.c on >> bare metal, the modified kernel will complain about spurious irq and >> disable the irq line. > > ok that's useful info for the changelog. > Will document them.
>> >> >> >> We fold the emulation of this inversion inside the hpet logic. >> >> >> >> Signed-off-by: Liu Ping Fan <pingf...@linux.vnet.ibm.com> >> > >> > >> > Doesn't this affect cross-version migration? >> > E.g. imagine that you migrate between systems >> > with/without this fix. >> > >> No. the changing only affect "route >= ISA_NUM_IRQS", For linux >> guest, it use IRQ2/8 for hpet0/hpet1 which is reserved by kernel. It >> work without this fix (I think windows is the same). But the >> hpet_example.c(in linux) can not work without this fix. So no such >> run-time instance before this bug fix. >> >> Regards, >> Pingfan > > aha so the argument is it's already too broken to even mostly work, > we don't need to worry about migrating it to/from old qemu. > Yes :) Thanks, Pingfan
