[SeaBIOS] synching GPE0_BLK between OVMF and qemu

Gleb Natapov gleb at redhat.com
Fri Apr 27 20:09:56 CEST 2012

On Fri, Apr 27, 2012 at 07:24:48PM +0200, Laszlo Ersek wrote:
> On 04/27/12 17:12, Jordan Justen wrote:
> > On Fri, Apr 27, 2012 at 07:31, Laszlo Ersek <lersek at redhat.com> wrote:
> >> edk2's "OvmfPkg/AcpiTables/Platform.h" specifies GPE0_BLK at 0x40C,
> >> while qemu's "hw/acpi_piix4.c" expects the guest to access it at 0xAFE0.
> >> Which macro should be modified to get them in sync?
> > 
> > Do they need to be in sync?
> It appears to me so:
> https://bugzilla.redhat.com/show_bug.cgi?id=653382#c22
> > We set PBMA to 0x400 in OvmfPkg/Library/AcpiTimerLib/AcpiTimerLib.c,
> > so isn't 0x40c correct?
> Considering OVMF in isolation, I presume it's self-consistent.
> However, is it necessary (a) to group these ACPI registers closely
> together, (b) to base the "group" at 0x400?
> >From "5.2.9 Fixed ACPI Description Table (FADT)" in the ACPI spec (v5.0)
> it would appear OVMF can freely choose where to put GPE0_BLK, in both
> senses (ie. port address considered alone, and also in relation to the
> other ACPI registers).
OVMF can't freely choose where to put GPE0_BLK. It should describe to
OSPM where GPE0_BLK is in HW. If it provides incorrect value this is
OVMF bug.

> Considering SeaBIOS again (build_fadt()):
> - PORT_ACPI_PM_BASE is 0xb000,
> - PM1a_EVT_BLK, PM1a_CNT_BLK and PM_TMR_BLK are located consecutively
> from this base,
> - but GPE0_BLK is placed at 0xafe0 (build_fadt() -->
> pci_init_device(fadt_init_tbl) --> piix4_fadt_init())
That is because those are two totally different things. One is PM1
register another is GPE0 register. The very obvious hint that they are
unrelated is that they described by two different fields in FADT.
> But I'm likely missing something ^W everything...
> Thanks!
> Laszlo


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