From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH] MSI / MSIX injection for Xen HVM
Date: Thu, 01 Mar 2012 16:56:47 +0100
Message-ID: <4F4F9C3F.5020201@redhat.com>
References: <1330536077.10387.57.camel@leeds.uk.xensource.com>
	<4F4E64B5.5080900@siemens.com>
	<1330597236.10387.70.camel@leeds.uk.xensource.com>
	<4F4F5BF5.6010206@siemens.com>
	<1330602678.10387.73.camel@leeds.uk.xensource.com>
	<4F4F71F0.4070109@redhat.com>
	<alpine.DEB.2.00.1203011403140.923@kaball-desktop>
	<4F4F81AE.9080503@redhat.com>
	<alpine.DEB.2.00.1203011446190.923@kaball-desktop>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Return-path: <qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org>
In-Reply-To: <alpine.DEB.2.00.1203011446190.923@kaball-desktop>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org
Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>, xen-devel <xen-devel@lists.xensource.com>, "Wei Liu (Intern)" <wei.liu2@citrix.com>, QEMU-devel <qemu-devel@nongnu.org>
List-Id: xen-devel@lists.xenproject.org

Il 01/03/2012 15:50, Stefano Stabellini ha scritto:
>>> > > That is a good point actually: we already have lapic emulation in Xen,
>>> > > it makes sense to have apic-msi in Xen too.
>>> > > We would still need the changes to msi_notify and msix_notify though.
>> > 
>> > Why?  The stores would just go to the Xen interrupt controller MMIO area
>> > which then does the xc_hvm_inject_msi.
>  
> Because msi(x)_notify is called by QEMU's emulated devices: it is not
> possible from QEMU to cause an emulation trap in Xen on behalf of the
> guest.

msi{x,}_notify doesn't have to go to Xen MMIO emulation, so in Wei's
patch you don't need anymore the msi{,x}_notify parts, only apic_send_msi.

But you could take it further and create a separate subclass of
apic-common that does absolutely nothing except register an MMIO memory
region and use it to trap MSI writes.  Basically an even more stripped
down version than hw/kvm/apic.c, but using memory_region_init_io rather
than memory_region_init_reservation.  You would also get support for the
monitor command inject-nmi (there is another hypercall for that in Xen
IIRC).

Paolo