linux-kernel - Re: QEMU fw_cfg DMA interface

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Date:	Thu, 6 Aug 2015 13:40:24 +0100
From:	Stefan Hajnoczi <stefanha@...il.com>
To:	Marc Marí <markmb@...hat.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	qemu-devel <qemu-devel@...gnu.org>, seabios@...bios.org,
	Drew <drjones@...hat.com>, "Kevin O'Connor" <kevin@...onnor.net>,
	Gerd Hoffmann <kraxel@...hat.com>, Laszlo <lersek@...hat.com>
Subject: Re: QEMU fw_cfg DMA interface

On Thu, Aug 6, 2015 at 1:37 PM, Marc Marí <markmb@...hat.com> wrote:
> On Thu, 6 Aug 2015 13:27:16 +0100
> Stefan Hajnoczi <stefanha@...il.com> wrote:
>
>> On Thu, Aug 6, 2015 at 12:00 PM, Marc Marí <markmb@...hat.com> wrote:
>> > When running a Linux guest on top of QEMU, using the -kernel
>> > options, this is the timing improvement for x86:
>> >
>> > QEMU commit 2be4f242b50a8 and SeaBIOS commit 908a58c1d5ff
>> > QEMU startup time: .078
>> > BIOS startup time: .060
>> > Kernel setup time: .578
>> > Total time: .716
>> >
>> > QEMU with this patch series and SeaBIOS with this patch series
>> > QEMU startup time: .080
>> > BIOS startup time: .039
>> > Kernel setup time: .002
>> > Total time: .121
>>
>> Impressive results!
>>
>> Is this a fully-featured QEMU build or did you disable things?
>>
>> Is this the default SeaBIOS build or did you disable things?
>>
>
> This is the default QEMU configuration I get for my system. It's not a
> fully-featured QEMU, but it has a lot of things enabled. SeaBIOS
> has a default configuration (with debugging disabled).

That's great.

Since SeaBIOS is a default configuration, the remaining BIOS startup
time is amenable to more optimizations in the future.

Stefan
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