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From: Kevin O'Connor <kevin@koconnor.net>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>, John Snow <jsnow@redhat.com>,
	qemu-devel <qemu-devel@nongnu.org>,
	"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] Recent SeaBIOS too big for QEMU -initrd
Date: Wed, 20 Aug 2014 18:17:40 -0400	[thread overview]
Message-ID: <20140820221739.GA10152@morn.localdomain> (raw)
In-Reply-To: <CAJSP0QW570KVTSg5wgML0_9Y9pfORCFLL4757OUzvq572q6zHQ@mail.gmail.com>

On Wed, Aug 20, 2014 at 11:27:41AM +0100, Stefan Hajnoczi wrote:
> The QEMU -initrd option loads the initrd at the top of RAM.  There is
> a 64 KB safety region for ACPI tables in hw/i386/pc.c:load_linux():
> 
>   initrd_max = max_ram_size-ACPI_DATA_SIZE-1;
> 
> QEMU's bios-256k.bin SeaBIOS build reserves 128 KB at the top of
> memory so the 64 KB ACPI data size has become too small.

Just to clarify, SeaBIOS uses a variable amount of data at the top of
ram.  SeaBIOS isn't changing the allocation because of its build
parameters, but because QEMU is passing more ACPI tables to it.

> Perhaps QEMU -> SeaBIOS -> linuxboot.bin can be simplified so QEMU
> doesn't have to guess what e820 region SeaBIOS will reserve.
> linuxboot.bin would probably be the place to do it unless SeaBIOS has
> Linux loading functionality that could be reused.

There is no current functionality in SeaBIOS to deploy a Linux kernel
from fw_cfg.  However, it looks like it would be pretty simple to add
if someone wants to give it a try.

-Kevin

      parent reply	other threads:[~2014-08-20 22:17 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-20 10:27 [Qemu-devel] Recent SeaBIOS too big for QEMU -initrd Stefan Hajnoczi
2014-08-20 11:27 ` Michael S. Tsirkin
2014-08-20 12:58   ` Stefan Hajnoczi
2014-08-20 20:58 ` Michael S. Tsirkin
2014-08-20 22:17 ` Kevin O'Connor [this message]

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