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Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios
From: |
Kevin O'Connor |
Subject: |
Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios |
Date: |
Wed, 25 Nov 2009 17:53:49 -0500 |
User-agent: |
Mutt/1.5.19 (2009-01-05) |
On Wed, Nov 25, 2009 at 11:04:20PM +0100, Sebastian Herbszt wrote:
>> Do different things during reset depending on CMOS values doesn't sound
>> right to me. I don't know what is implemented right now. I thought that
>> we reload BIOS on reset.
>
> Currently the BIOS seems to be only loaded once and not reloaded
> during the life time of a VM.
> I don't think there is a notion of BIOS reload on real hardware. CPU
> access to it is either directed to the rom (power-up configuration,
> all those fancy reset conditions) or to ram.
I see a "BIOS reload" as equivalent to directing access to rom.
> How is shadowing currently implemented in qemu? Is the only BIOS
> copy overwritten or is the rom copy separate from the ram copy?
My understanding is that both the ram and rom are kept. (Though, on a
"BIOS reload" I don't know if the ram is preserved.)
To summarize the discussion so far, there seems to be a potential
issue with reset:
* If qemu doesn't reload the bios (a soft-reset) then there is a
potential issue with the bios and option roms not running properly
after a system reset invoked by Linux or other modern OSs.
* If qemu does reload the bios (a hard-reset) then there is a good
chance that old DOS programs will break when they invoke a reset in
an attempt to switch from protected mode to real mode.
Is that correct?
-Kevin
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, (continued)
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Jamie Lokier, 2009/11/24
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Gleb Natapov, 2009/11/24
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Jamie Lokier, 2009/11/25
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Gleb Natapov, 2009/11/25
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Kevin O'Connor, 2009/11/25
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Gleb Natapov, 2009/11/25
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Sebastian Herbszt, 2009/11/25
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Jamie Lokier, 2009/11/26
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Sebastian Herbszt, 2009/11/27
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Sebastian Herbszt, 2009/11/25
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios,
Kevin O'Connor <=
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Gleb Natapov, 2009/11/26
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Kevin O'Connor, 2009/11/26
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Gleb Natapov, 2009/11/26
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Kevin O'Connor, 2009/11/26
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Gleb Natapov, 2009/11/26
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Kevin O'Connor, 2009/11/26
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Gleb Natapov, 2009/11/26
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Kevin O'Connor, 2009/11/26
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Sebastian Herbszt, 2009/11/26
- Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios, Kevin O'Connor, 2009/11/27