Re: [Qemu-devel] [PATCH v3 0/4] Introduce the microvm machine type

From: Igor Mammedov <imammedo@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>,
	Eduardo Habkost <ehabkost@redhat.com>,
	Sergio Lopez <slp@redhat.com>,
	Maran Wilson <maran.wilson@oracle.com>,
	Stefan Hajnoczi <stefanha@gmail.com>,
	QEMU Developers <qemu-devel@nongnu.org>,
	Gerd Hoffmann <kraxel@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Richard Henderson <rth@twiddle.net>,
	Stefano Garzarella <sgarzare@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v3 0/4] Introduce the microvm machine type
Date: Fri, 26 Jul 2019 14:46:15 +0200	[thread overview]
Message-ID: <20190726144615.6ed811de@redhat.com> (raw)
In-Reply-To: <20190725133500-mutt-send-email-mst@kernel.org>

On Thu, 25 Jul 2019 13:38:48 -0400
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Thu, Jul 25, 2019 at 05:39:39PM +0200, Paolo Bonzini wrote:
> > On 25/07/19 17:01, Michael S. Tsirkin wrote:  
> > >> It would be educational to try to enable ACPI core but disable all
> > >> optional features.  
> > 
> > A lot of them are select'ed so it's not easy.
> >   
> > > Trying with ACPI_REDUCED_HARDWARE_ONLY would also be educational.  
> > 
> > That's what the NEMU guys experimented with.  It's not supported by our
> > DSDT since it uses ACPI GPE,  
> 
> Well there are two GPE blocks in FADT. We could just switch to
> these if necesary I think.

if it's simplistic vm we could build dedicated DSDT (or whole set of tables)
for it and use reduced profile like arm-virt machine does (just a newer
version of FADT with need flags set). That probably would cut acpi cost on
QEMU side.

> > and the reduction in code size is small
> > (about 15000 lines of code in ACPICA, perhaps 100k if you're lucky?).
> > 
> > Paolo  
> 
> Well ACPI is 150k loc I think, right?
> 
> linux]$ wc -l `find drivers/acpi/ -name '*.c' `|tail -1
>  145926 total
> 
> So 100k wouldn't be too shabby.
> 