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Date: Wed, 27 May 2015 11:30:19 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] Announcing qboot, a minimal x86 firmware for QEMU
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To: Christopher Covington <cov@codeaurora.org>, "Daniel P. Berrange" <berrange@redhat.com>, Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-devel <qemu-devel@nongnu.org>, KVM list <kvm@vger.kernel.org>



On 26/05/2015 23:25, Christopher Covington wrote:
> On 05/25/2015 08:53 AM, Paolo Bonzini wrote:
>>
>> On 22/05/2015 13:12, Daniel P. Berrange wrote:
>>> In
>>> particular I don't see why we need to have a SATA controller and ISA/LPC
>>> bridge in every virt machine - root PCI bus only should be possible, as you
>>> can provide disks via virtio-blk or virtio-scsi and serial, parallel, mouse,
>>> floppy via PCI devices and/or by adding a USB bus in the cases where you
>>> really need one.
>>
>> I think removing the ISA/LPC bridge is hard.  It includes the real-time
>> clock and fw_cfg, for example.
> 
> Could VirtIO specified replacements make sense for these peripherals?

Not really.  virtio is too heavyweight and you'd be reinventing the
wheel unnecessarily.

For example, ARM's "-M virt" uses a pl011 block for the RTC, and also
uses fw_cfg.  Another commonly used ISA device is the UART, for which
again -M virt uses a pl031.

Paolo