From: David Gibson <dwg@au1.ibm.com>
To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Peter Maydell <peter.maydell@linaro.org>,
Avik Sil <aviksil@linux.vnet.ibm.com>,
qemu-devel@nongnu.org, Alex Graf <agraf@suse.de>
Subject: Re: [Qemu-devel] nvram and boot order
Date: Wed, 17 Oct 2012 12:01:07 +1100 [thread overview]
Message-ID: <20121017010107.GZ4640@truffula.fritz.box> (raw)
In-Reply-To: <874nluqaeh.fsf@codemonkey.ws>
On Tue, Oct 16, 2012 at 06:12:22PM -0500, Anthony Liguori wrote:
> Peter Maydell <peter.maydell@linaro.org> writes:
>
> > On 16 October 2012 20:55, Anthony Liguori <aliguori@us.ibm.com> wrote:
> >>
> >> We discussed nvram and it's interaction with boot order in today's KVM
> >> call. Here's the outcome. This list is completely incremental so it's
> >> fine to start with 1-4, for instance, as long as we eventually get to 6.
> >>
> >> Today, on x86, we implement up to (5) but we don't persist NVRAM.
> >>
> >> 1) We should modify QEMUMachine to specify that a machine does not want
> >> a default boot order. Ideally, this would be done by adding a new
> >> default_boot_order that is set to "cad" explicitly in all machines
> >> allowing a machine to remove that entry. At any rate, this allows a
> >> machine to receive a NULL boot order when -boot isn't used and take an
> >> appropriate action accordingly.
> >>
> >> 2) In the absence of a persistent NVRAM, a ephemeral NVRAM should be
> >> generated with a reasonable default boot order.
> >>
> >> 3) In the absence of -boot or ,bootindex=, the system should boot from
> >> order specified in NVRAM.
> >>
> >> 4) If -boot is specified, the parameter should alter the contents of
> >> NVRAM to change the boot order to what is specified by -boot.
> >>
> >> 5) If ,bootorder is specified, it should take predence over -boot.
> >>
> >> 6) ,bootorder= should also alter the contents of NVRAM to determine the
> >> boot order.
> >
> > What's the rationale for 6? It seems a bit odd for a command line
> > option to randomly mangle the NVRAM...
>
> The use case is to have a consistent view of the boot order within the
> guest and in the host while still having the ability to edit the
> persistent boot order within the guest.
>
> If you look at my other note in this thread, one way to achieve this is
> to have the boot order "owned" by QEMU with the guest making fw_cfg
> calls to modify it. It would be persisted in a portion of the NVRAM
> reserved for QEMU's use.
That's not necessarily compatible with established guest visible
platform NVRAM semantics.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
next prev parent reply other threads:[~2012-10-17 1:01 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-16 19:55 [Qemu-devel] nvram and boot order Anthony Liguori
2012-10-16 20:07 ` Benjamin Herrenschmidt
2012-10-16 20:55 ` Anthony Liguori
2012-10-26 6:27 ` David Gibson
2012-10-17 13:48 ` Gleb Natapov
2012-10-16 20:13 ` Peter Maydell
2012-10-16 23:12 ` Anthony Liguori
2012-10-17 1:01 ` David Gibson [this message]
2012-10-17 0:58 ` David Gibson
2012-10-17 18:17 ` Anthony Liguori
2012-10-18 0:09 ` David Gibson
2012-10-18 1:18 ` Benjamin Herrenschmidt
2012-10-18 6:32 ` Alexander Graf
2012-10-19 8:24 ` David Gibson
2012-10-19 8:40 ` Alexander Graf
2012-10-25 4:14 ` David Gibson
2012-10-19 14:21 ` Anthony Liguori
2012-10-19 14:36 ` Peter Maydell
2012-10-19 18:11 ` Benjamin Herrenschmidt
2012-10-19 17:29 ` Blue Swirl
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