Re: [Qemu-devel] [RFC PATCH 6/6] hw/i386: deprecate the "isapc" machine

From: Thomas Huth <thuth@redhat.com>
To: Gerd Hoffmann <kraxel@redhat.com>,
	"Daniel P. Berrange" <berrange@redhat.com>
Cc: "Philippe Mathieu-Daudé" <f4bug@amsat.org>,
	"Peter Maydell" <peter.maydell@linaro.org>,
	"Eduardo Habkost" <ehabkost@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	qemu-devel@nongnu.org,
	"Alistair Francis" <alistair.francis@xilinx.com>,
	"Marcel Apfelbaum" <marcel@redhat.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Richard Henderson" <rth@twiddle.net>
Subject: Re: [Qemu-devel] [RFC PATCH 6/6] hw/i386: deprecate the "isapc" machine
Date: Wed, 8 Nov 2017 11:05:15 +0100	[thread overview]
Message-ID: <470e67ec-fe1e-2692-c14c-5c843a9d3053@redhat.com> (raw)
In-Reply-To: <20171108094421.ta2wumq36gux3m5s@sirius.home.kraxel.org>

On 08.11.2017 10:44, Gerd Hoffmann wrote:
> On Wed, Nov 08, 2017 at 09:09:00AM +0000, Daniel P. Berrange wrote:
>> On Tue, Nov 07, 2017 at 11:28:28PM -0300, Philippe Mathieu-Daudé wrote:
>>> Deprecated since 2.9.0, guests should be able to use "pc" instead.
>>
>> Isn't isapc important to allow QEMU to old operating systems that
>> predate the PCI era.
> 
> They should work fine.  The early pci chipsets like the piix4 have
> built-in backward compatibility.  The IDE controller can be driven by
> simply accessing the isa ide ports.  Likewise vga.  You can plug in ne2k
> (we have both isa and pci variants) for ethernet and sb16 (isa too) for
> sound.
> 
> That should make guests which don't know anything about pci happy.
> 
>> I do recall seeing some messages about specific
>> cases where you cannot use the 'pc' machine type and we suggested
>> used of 'isapc' instead, but can't remember the exact details..
> 
> I'd like to see such use cases where isapc is actually required.

Just my 0.02 €: I like the idea of keeping isapc. It's a way to remind
the x86 folks that there are also architectures without PCI / APIC /
ACPI. And this helped to spot some bugs in some HMP commands in the past
already.

> Well, nobody maintains it.  Nobody tests it.

At least we've got the automatic boot-serial-test now that checks that
the machine is not completely broken.

 Thomas