Re: [Qemu-devel] [PATCH v2] x86: gigabyte alignment for ram

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 20 Jan 2014 17:51:47 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Mon, Jan 20, 2014 at 04:36:57PM +0100, Gerd Hoffmann wrote:
> > > 4.1.2.
> > >  MCFG Table Description
> > > 
> > > 
> > > ...
> > > 
> > > If the operating system does not natively comprehend reserving the MMCFG
> > > region, the MMCFG region must be reserved by firmware. The address range
> > > reported in the MCFG table or by _CBA method (see Section 4.1.3) must be
> > > reserved by declaring a motherboard resource.
> > 
> > We don't do this today.
> > 
> > > For most systems, the
> > > motherboard resource would appear at the root of the ACPI namespace
> > > (under \_SB) in a node with a _HID of EISAID (PNP0C02), and the
> > > resources in this case should not be claimed in the root PCI bus’s _CRS.
> > 
> > Which I read as _in case it is at the root of the apci namespace_ it
> > should not be claimed in PCI0._CRS.  Which makes sense.
> > 
> > My laptop has it reserved in a \_SB\PCI0\LPC\SIO device instead:
> > 
> >             Device (LPC)
> >             {
> >                 Name (_ADR, 0x001F0000)  // _ADR: Address
> >                 Name (_S3D, 0x03)  // _S3D: S3 Device State
> >                 Name (RID, 0x00)
> >                 Device (SIO)
> >                 {
> >                     Name (_HID, EisaId ("PNP0C0P2"))
> >                     Name (_UID, 0x00)  // _UID: Unique ID
> >                     Name (SCRS, ResourceTemplate ()
> >                     {
> >                         [ ... ]
> >                         Memory32Fixed (ReadWrite,
> >                             0xF8000000,         // Address Base
> >                             0x04000000,         // Address Length
> >                             )
> >                         [ ... ]
> > 
> > cheers,
> >   Gerd
> > 
> 
> We can try, but Igor tried to do something like this recently (
> for IO resources) and windows guests kept crashing
> unless he made holes in _CRS.
I've tried to consume ranges under piix_pm/lpc device,
there were no any indication that ranges were ever consumed.

I haven't tried to put PNP0C0P2 on PCI bus though. It might work
I just found similar code in coreboot
https://www.mail-archive.com/coreboot@coreboot.org/msg27723.html