From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51660) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zypqz-0006Qy-N5 for qemu-devel@nongnu.org; Tue, 17 Nov 2015 18:40:02 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zypqw-0001MP-E8 for qemu-devel@nongnu.org; Tue, 17 Nov 2015 18:40:01 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59182) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zypqw-0001MH-8s for qemu-devel@nongnu.org; Tue, 17 Nov 2015 18:39:58 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (Postfix) with ESMTPS id 63E0EA852 for ; Tue, 17 Nov 2015 23:39:57 +0000 (UTC) From: Bandan Das References: <1447397748-24920-1-git-send-email-bsd@redhat.com> <1447397748-24920-3-git-send-email-bsd@redhat.com> <87y4dwpu2a.fsf@blackfin.pond.sub.org> Date: Tue, 17 Nov 2015 18:39:55 -0500 In-Reply-To: <87y4dwpu2a.fsf@blackfin.pond.sub.org> (Markus Armbruster's message of "Tue, 17 Nov 2015 15:41:17 +0100") Message-ID: MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH v3 2/2] i440fx: print an error message if user tries to enable iommu List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: qemu-devel@nongnu.org, mst@redhat.com Markus Armbruster writes: > Bandan Das writes: > >> There's no indication of any sort that i440fx doesn't support >> "iommu=on" >> >> Reviewed-by: Eric Blake >> Signed-off-by: Bandan Das >> --- >> hw/pci-host/piix.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c >> index 7b2fbf9..715208b 100644 >> --- a/hw/pci-host/piix.c >> +++ b/hw/pci-host/piix.c >> @@ -34,6 +34,7 @@ >> #include "sysemu/sysemu.h" >> #include "hw/i386/ioapic.h" >> #include "qapi/visitor.h" >> +#include "qemu/error-report.h" >> >> /* >> * I440FX chipset data sheet. >> @@ -301,6 +302,10 @@ static void i440fx_pcihost_realize(DeviceState *dev, Error **errp) >> static void i440fx_realize(PCIDevice *dev, Error **errp) >> { >> dev->config[I440FX_SMRAM] = 0x02; >> + >> + if (object_property_get_bool(qdev_get_machine(), "iommu", NULL)) { >> + error_report("warning: i440fx doesn't support emulated iommu"); >> + } >> } >> >> PCIBus *i440fx_init(const char *host_type, const char *pci_type, > > Hmm. > > If I understand things correctly, we add property "iommu" to *any* > machine, whether it supports it or not (see machine_initfn() in > hw/core/machine.c). > > Most machines don't support it. You add a warning to one of them. Yeah, I guess the only one that does is q35. Although, iommu should be theoretically applicable to all machine types, a generic "iommu" property common to all types makes little sense to me. One way is to remove the common property and make "iommu" a property of Q35 only (through a custom instance_init). Other is to simply make the property common to pc by moving it to pc.c But that still doesn't solve the problem since i440fx cannot emulate it yet. > Why to that one and not the others? > > Shouldn't we add properties only to machines where they make sense? > Adding them indiscrimiately defeats QOM introspection. For now, maybe we can just skip this patch. I will post another generic solution. It's just weird that qemu runs happily without complaining when iommu is specified with an unsupported type.