Re: [Qemu-devel] QEMU 3.0 ?

From: Paolo Bonzini <pbonzini@redhat.com>
To: Cornelia Huck <cohuck@redhat.com>
Cc: "Thomas Huth" <thuth@redhat.com>,
	"Peter Maydell" <peter.maydell@linaro.org>,
	"Cédric Le Goater" <clg@kaod.org>,
	"QEMU Developers" <qemu-devel@nongnu.org>,
	"David Gibson" <david@gibson.dropbear.id.au>,
	"Greg Kurz" <groug@kaod.org>,
	"Markus Armbruster" <armbru@redhat.com>,
	"Daniel P. Berrange" <berrange@redhat.com>,
	"Eric Blake" <eblake@redhat.com>,
	"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
	sergio.g.delreal@gmail.com, alex@alex.org.uk
Subject: Re: [Qemu-devel] QEMU 3.0 ?
Date: Thu, 23 Nov 2017 13:26:14 +0100	[thread overview]
Message-ID: <b3b9837e-c6b0-d718-faaf-1ef198256634@redhat.com> (raw)
In-Reply-To: <20171123130908.6ab004d3.cohuck@redhat.com>

On 23/11/2017 13:09, Cornelia Huck wrote:
> On Thu, 23 Nov 2017 13:05:33 +0100
> Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
>> On 23/11/2017 12:57, Thomas Huth wrote:
>>> On 23.11.2017 12:17, Paolo Bonzini wrote:  
>>>> On 23/11/2017 11:57, Thomas Huth wrote:  
>>> [...]  
>>>>> I've put "--accel kvm:hax:tcg" also on the doable list since I don't
>>>>> remember any objections to that idea so far -- feel free to move it to
>>>>> the controversial list instead if you think it needs more discussion.  
>>>>
>>>> "hax" is very far from feature parity with TCG, it doesn't even support
>>>> CPUID (-cpu).  "-accel kvm:hvf:tcg" could be a possibility, but only if
>>>> we have resources to test it.  As far as I know the only active x86
>>>> developer who owns a Mac is Igor?  
>>>
>>> hvf hasn't been merged yet ... do you expect it to hit master after 2.11
>>> has been released?  
>>
>> Yes, more or less.
>>
>>> Otherwise, we should maybe rather simply go with
>>> "--accel kvm:tcg"?  
>>
>> Yes, HVF can come later.
> 
> This switch sounds like something we can easily do for the next
> release; I'd hope that anyone explicitly requiring tcg already
> specifies it.

I seriously doubt that.  Most people are probably using a
distro-provided qemu-kvm script for KVM, and qemu-system-x86_64 for TCG.
 In fact, that is probably the best of both worlds for anybody who
doesn't compile its own QEMU; and since KVM is Linux-only, there are
very few non-developers in the intersection of "compile its own QEMU"
and "use KVM".

And in fact that is the main reason why have never bothered switching
the default... only RHEL does it, because it ships the QEMU binary as
qemu-kvm rather than qemu-system-xxx plus a wrapper script.

Perhaps we could:

1) look for "qemu-{kvm,hvf,hax}" in argv[0] and change the "-accel" default?

2) change "make install" to install one or more of qemu-kvm/hvf/hax
based on target architecture and OS.

Then distros can do away with the script and Windows/Mac users can learn
to use qemu-hvf and qemu-hax.

Paolo