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Re: [Qemu-devel] [PATCH v3 2/2] pc: Fix RTC CMOS info on RAM for ram_siz
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From: |
Kevin O'Connor |
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Subject: |
Re: [Qemu-devel] [PATCH v3 2/2] pc: Fix RTC CMOS info on RAM for ram_size < 1MiB |
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Date: |
Sun, 19 Aug 2012 15:36:07 -0400 |
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User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Wed, Aug 15, 2012 at 01:12:20PM +0200, Markus Armbruster wrote:
> pc_cmos_init() always claims 640KiB base memory, and ram_size - 1MiB
> extended memory. The latter can underflow to "lots of extended
> memory". Fix both, and clean up some.
>
> Note: SeaBIOS currently requires 1MiB of RAM, and doesn't check
> whether it got enough.
SeaBIOS (and Bochs BIOS before it) never checked cmos 0x15-0x18 for
memory sizes. Thus, it has only ever supported passing memory in 1MiB
chunks. If we really want to communicate fine grained memory sizes, I
suggest passing an e820 like map via fw_cfg to SeaBIOS. I don't think
it makes sense for SeaBIOS to read new magic cmos settings just to
check if it should crash in a slightly different way.
-Kevin