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Re: [Qemu-devel] PC machine types switched to SeaBIOS/gPXE

From: Kevin O'Connor
Subject: Re: [Qemu-devel] PC machine types switched to SeaBIOS/gPXE
Date: Mon, 2 Nov 2009 23:50:56 -0500
User-agent: Mutt/1.5.19 (2009-01-05)

On Mon, Nov 02, 2009 at 03:56:08PM +0200, Avi Kivity wrote:
> On 11/02/2009 03:51 PM, Kevin O'Connor wrote:
>> On Mon, Nov 02, 2009 at 03:32:54PM +0200, Avi Kivity wrote:
>>> Is seabios clobbering memory?  Gleb/Kevin?
>> I have not tested with the -kernel option before.  I believe you may
>> be running into the clearing of memory that PMM does - see
>> malloc_finalize() in src/pmm.c.  The PMM spec requires that low memory
>> be cleared before starting the boot process.
> Likely.  Alex, does -kernel use memory below 1MB?  Can it be moved  
> elsewhere?

I've confirmed that commenting out the memset in malloc_finalize()
fixes the reported problem.

Removing the memset is probably okay for the short-term, but it would
contradict the PMM spec, so we'll need some kind of long-term

Also, SeaBIOS wont clear high-memory, but nothing stops SeaBIOS from
using high memory for scratch space during init.

> If not, we probably need a protocol where the option rom loads the  
> kernel from qemu, rather than qemu poking the kernel into memory.

Yes, I'd prefer to see this.  In earlier emails, Gleb made a reference
to a qemu-cfg "stream" interface that is used for acpi tables - maybe
the kernel could be put in one of the streams and the rom could copy
it into ram on boot.

Let me know what you wish to do.

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