From: Stefan Hajnoczi <stefanha@gmail.com>
To: Kevin O'Connor <kevin@koconnor.net>
Cc: Daniel Castro <evil.dani@gmail.com>,
xen-devel@lists.xensource.com, seabios@seabios.org
Subject: Re: Ideas for PV on SeaBIOS
Date: Mon, 23 May 2011 06:24:07 +0100 [thread overview]
Message-ID: <BANLkTi=jNak8neUhDdZ+qUKVzz1qM_xC5A@mail.gmail.com> (raw)
In-Reply-To: <20110521132948.GA9679@morn.localdomain>
On Sat, May 21, 2011 at 2:29 PM, Kevin O'Connor <kevin@koconnor.net> wrote:
> On Thu, May 19, 2011 at 02:33:52PM +0900, Daniel Castro wrote:
>> Good Day,
>>
>> In order to give PV Drivers to SeaBIOS we will need to solve a few
>> problems, one is the following:
>> Does a booting kernel informs the BIOS that it will leave real mode
>> and not use it again? When the booting kernel uses CPU real mode for
>> the last time, how can we (Xen or SeaBIOS) know that real mode will no
>> longer be used, and hence BIOS calls will not be issued?
>
> In the general case, no.
>
> The ACPI spec does define a mechanism for the OS to inform the BIOS
> that it is transitioning from "Legacy state" to "Working state" via an
> SMI. SeaBIOS does have code for this (see src/smm.c), but it doesn't
> currently do anything interesting. Unfortunately, this is only
> available for OSs that support ACPI.
>
>> We want upon last real mode usage to leave all Xen PV information in a
>> clean state, this means, closing the channel and ring between the
>> newly created domain and the host system.
>
> Is it required to close the channel? Can opening a new channel
> implicitly close the old channel (I believe this is what the virtio
> stuff does)?
There ought to be a way for the guest to reset the device. At least
in virtio this can be done and allows an in-use device to be reused,
no matter what state it is in.
Stefan
next prev parent reply other threads:[~2011-05-23 5:24 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-19 5:33 Ideas for PV on SeaBIOS Daniel Castro
2011-05-19 7:19 ` Keir Fraser
2011-05-19 8:01 ` [Xen-devel] " Ian Campbell
2011-05-21 7:39 ` Paolo Bonzini
2011-05-21 8:44 ` James Harper
2011-05-23 9:23 ` [Xen-devel] " Ian Campbell
2011-05-23 10:20 ` James Harper
2011-05-23 10:23 ` Ian Campbell
2011-05-19 7:44 ` James Harper
2011-05-19 8:08 ` Jan Beulich
2011-05-19 8:17 ` Juergen Gross
2011-05-19 8:20 ` Tim Deegan
2011-05-19 9:36 ` Ian Campbell
2011-05-19 15:02 ` Keir Fraser
2011-05-19 17:00 ` Ideas for PV on SeaBIOS - flush/barrier in QEMU Konrad Rzeszutek Wilk
2011-05-19 9:32 ` Ideas for PV on SeaBIOS James Harper
2011-05-21 13:38 ` [SeaBIOS] " Kevin O'Connor
2011-05-21 13:29 ` Kevin O'Connor
2011-05-23 5:24 ` Stefan Hajnoczi [this message]
2011-05-23 9:50 ` Ian Campbell
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