[SeaBIOS] [PATCH] mark VBE mapping as reserved in e820

Carl-Daniel Hailfinger c-d.hailfinger.devel.2006 at gmx.net
Mon Jan 25 05:40:50 CET 2010

On 24.01.2010 18:18, Izik Eidus wrote:
> On Sun, 24 Jan 2010 17:45:25 +0100
> Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net> wrote:
>> That looks like a bug. If you're talking about an ISA device, the LFB
>> must be smaller than 16 MB and its upper end must be at 16 MB or below.
>> If you only allow power-of-two sizes, the maximum LFB size is 8 MB
>> located at 8 MB. (LFB size of 16 MB is not allowed because it would mean
>> the lowest 640 kB are part of the LFB.)
>> If the device is EISA (instead of ISA) it can work, but I think you need
>> the full PNPBIOS extensions for it to work (AFAIK isapnptools have
>> readable docs/code and could help to find out what is needed).
> I think this code probably fall into the eisa catagory,

Yes, probably.

> But I am confused about what the direction you offer to
> solve this problem.

If it is pure ISA, I do not think we can solve the problem unless we
place a 8 MB LFB at address 8-16 MB.
If it is EISA, I propose to use the PNPBIOS extensions because most OS
check these extensions before allocating (PCI) resources.

> The acpi spec does mention that PNP devices does not have to
> be reported.

Hm. If the PNP devices are not reported in the ACPI tables, they should
still be visible via the PNPBIOS extensions. We may have to extend the
VGABIOS or SeaBIOS for this (I didn't check).

> But considering the qemu code we have right now I think this is
> the only right fix to make the isa_sta_vga safe.

"this" == Adding the devices to the ACPI table?


Developer quote of the year:
"We are juggling too many chainsaws and flaming arrows and tigers."

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