[SeaBIOS] [RFC PATCH v3 06/19] Implement "-dimm" command line option

Vasilis Liaskovitis vasilis.liaskovitis at profitbricks.com
Mon Oct 22 10:39:49 CEST 2012


Hi,
On Thu, Oct 18, 2012 at 02:33:02PM +0200, Avi Kivity wrote:
> On 10/18/2012 11:27 AM, Vasilis Liaskovitis wrote:
> > On Wed, Oct 17, 2012 at 12:03:51PM +0200, Avi Kivity wrote:
> >> On 10/17/2012 11:19 AM, Vasilis Liaskovitis wrote:
> >> >> 
> >> >> I don't think so, but probably there's a limit of DIMMs that real
> >> >> controllers have, something like 8 max.
> >> > 
> >> > In the case of i440fx specifically, do you mean that we should model the DRB
> >> > (Dram row boundary registers in section 3.2.19 of the i440fx spec) ?
> >> > 
> >> > The i440fx DRB registers only supports up to 8 DRAM rows (let's say 1 row
> >> > maps 1-1 to a DimmDevice for this discussion) and only supports up to 2GB of
> >> > memory afaict (bit 31 and above is ignored).
> >> > 
> >> > I 'd rather not model this part of the i440fx - having only 8 DIMMs seems too
> >> > restrictive. The rest of the patchset supports up to 255 DIMMs so it would be a
> >> > waste imho to model an old pc memory controller that only supports 8 DIMMs.
> >> > 
> >> > There was also an old discussion about i440fx modeling here:
> >> > https://lists.nongnu.org/archive/html/qemu-devel/2011-07/msg02705.html
> >> > the general direction was that i440fx is too old and we don't want to precisely
> >> > emulate the DRB registers, since they lack flexibility.
> >> > 
> >> > Possible solutions:
> >> > 
> >> > 1) is there a newer and more flexible chipset that we could model?
> >> 
> >> Look for q35 on this list.
> > 
> > thanks, I 'll take a look. It sounds like the other options below are more
> > straightforward now, but let me know if you prefer q35 integration as a priority.
> 
> At least validate that what you're doing fits with how q35 works.

In terms of pmc modeling, the q35 page http://wiki.qemu.org/Features/Q35
mentions:

Refactor i440fx to create i440fx-pmc class
ich9: model ICH9 Super I/O chip
ich9: make i440fx-pmc a generic PCNorthBridge class and add support for ich9
northbridge 

is this still the plan? There was an old patchset creating i440fx-pmc here:
http://lists.gnu.org/archive/html/qemu-devel/2012-01/msg03501.html
but I am not sure if it has been dropped or worked on. v3 of the q35 patchset
doesn't include a pmc I think.

It would be good to know what the current plan regarding pmc modeling (for both
q35 and i440fx) is.

thanks,

- Vasilis




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