From: Gerd Hoffmann <kraxel@redhat.com>
To: "Richard W.M. Jones" <rjones@redhat.com>
Cc: "Marc Marí" <markmb@redhat.com>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] Why is SeaBIOS used with -kernel?
Date: Mon, 21 Mar 2016 10:40:17 +0100 [thread overview]
Message-ID: <1458553217.4299.42.camel@redhat.com> (raw)
In-Reply-To: <20160321083739.GN1681@redhat.com>
Hi,
> > And the bulk of that is loading the kernel from fw_cfg.
>
> Yes after further investigation that is correct. It looks like
> fw_cfg has grown a DMA interface, but it's not used on x86.
>
> There is still a considerable amount of SeaBIOS overhead. In
> particular, it scans the whole of the PCI bus looking for boot
> devices, but that work is both slow and completely unnecessary if
> we're using the linuxbios option ROM to boot.
There have been some experiments to strip down seabios config to speed
up things.
At least on q35 we also might consider using mmconfig, which I think
will reduce the number of vmexits needed for pci config space access.
Oh, and there also is qboot from paolo, but I think this is more a
proof-of-concept thing to see where the limit is.
cheers,
Gerd
next prev parent reply other threads:[~2016-03-21 9:40 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-19 20:31 [Qemu-devel] Why is SeaBIOS used with -kernel? Richard W.M. Jones
2016-03-21 7:58 ` Gerd Hoffmann
2016-03-21 8:37 ` Richard W.M. Jones
2016-03-21 9:40 ` Gerd Hoffmann [this message]
2016-03-31 9:21 ` Stefan Hajnoczi
2016-03-31 16:22 ` Kevin O'Connor
[not found] ` <20160331221039.GA32728@redhat.com>
2016-03-31 22:17 ` Richard W.M. Jones
2016-03-31 22:44 ` Kevin O'Connor
2016-04-01 7:55 ` Richard W.M. Jones
2016-04-01 8:03 ` Paolo Bonzini
2016-04-01 8:47 ` Richard W.M. Jones
2016-04-01 8:51 ` Paolo Bonzini
2016-04-01 8:57 ` Richard W.M. Jones
2016-04-01 9:05 ` Paolo Bonzini
2016-04-01 8:02 ` Richard W.M. Jones
2016-04-01 8:11 ` Paolo Bonzini
2016-04-01 8:14 ` Richard W.M. Jones
2016-04-01 8:24 ` Paolo Bonzini
2016-04-01 8:44 ` Richard W.M. Jones
2016-04-01 8:47 ` Paolo Bonzini
2016-04-01 8:49 ` Vasiliy Tolstov
2016-04-01 9:16 ` Dr. David Alan Gilbert
2016-04-01 9:18 ` Gerd Hoffmann
2016-04-01 10:17 ` Richard W.M. Jones
2016-04-01 11:07 ` Gerd Hoffmann
2016-04-01 11:11 ` Richard W.M. Jones
2016-04-01 11:20 ` Richard W.M. Jones
2016-04-01 11:21 ` Paolo Bonzini
2016-04-01 11:26 ` Richard W.M. Jones
2016-04-05 4:38 ` Kevin Wolf
2016-04-05 8:04 ` Richard W.M. Jones
2016-04-05 8:11 ` Kevin Wolf
2016-04-05 9:19 ` Richard W.M. Jones
2016-04-05 9:26 ` Kevin Wolf
2016-04-01 11:32 ` Gerd Hoffmann
2016-04-01 11:49 ` Richard W.M. Jones
2016-04-01 15:35 ` Kevin O'Connor
2016-04-01 16:03 ` Paolo Bonzini
2016-04-01 18:41 ` Richard W.M. Jones
2016-04-01 18:59 ` Richard W.M. Jones
2016-04-01 19:04 ` Kevin O'Connor
2016-04-01 19:10 ` Richard W.M. Jones
2016-04-01 19:15 ` Richard W.M. Jones
2016-04-01 19:44 ` Kevin O'Connor
2016-04-01 20:25 ` Richard W.M. Jones
2016-04-01 20:05 ` Kevin O'Connor
2016-04-01 20:46 ` Richard W.M. Jones
2016-04-01 22:25 ` Kevin O'Connor
2016-04-02 7:51 ` Richard W.M. Jones
2016-04-02 5:30 ` Paolo Bonzini
2016-04-01 15:08 ` Kevin O'Connor
2016-04-01 14:58 ` Kevin O'Connor
2016-04-01 15:06 ` Richard W.M. Jones
2016-04-01 15:14 ` Kevin O'Connor
2016-04-01 8:19 ` Richard W.M. Jones
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