All of lore.kernel.org
 help / color / mirror / Atom feed
From: Stefan Hajnoczi <stefanha@gmail.com>
To: qemu-devel <qemu-devel@nongnu.org>
Cc: Kevin OConnor <kevin@koconnor.net>, John Snow <jsnow@redhat.com>,
	Gerd Hoffmann <kraxel@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>
Subject: [Qemu-devel] Recent SeaBIOS too big for QEMU -initrd
Date: Wed, 20 Aug 2014 11:27:41 +0100	[thread overview]
Message-ID: <CAJSP0QW570KVTSg5wgML0_9Y9pfORCFLL4757OUzvq572q6zHQ@mail.gmail.com> (raw)

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.

The guest Linux kernel rejects the initrd:
BIOS-provided physical RAM map:
 BIOS-e820: 0000000000010000 - 000000000009fc00 (usable)
 BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 000000003ffe0000 (usable)
 BIOS-e820: 000000003ffe0000 - 0000000040000000 (reserved)
 BIOS-e820: 00000000feffc000 - 00000000ff000000 (reserved)
 BIOS-e820: 00000000fffc0000 - 0000000100000000 (reserved)
...
initrd extends beyond end of memory (0x3ffef79f > 0x3ffe0000)
disabling initrd

It is easy enough to "fix" the problem by bumping ACPI_DATA_SIZE up to
0x20000 in QEMU.  Perhaps this should only be done for bios-256k.bin
guests and not bios-128k.bin guests (QEMU 1.7 and older machine
types).

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.

Any ideas?

Stefan

             reply	other threads:[~2014-08-20 10:35 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-20 10:27 Stefan Hajnoczi [this message]
2014-08-20 11:27 ` [Qemu-devel] Recent SeaBIOS too big for QEMU -initrd 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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAJSP0QW570KVTSg5wgML0_9Y9pfORCFLL4757OUzvq572q6zHQ@mail.gmail.com \
    --to=stefanha@gmail.com \
    --cc=jsnow@redhat.com \
    --cc=kevin@koconnor.net \
    --cc=kraxel@redhat.com \
    --cc=mst@redhat.com \
    --cc=qemu-devel@nongnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.