From: Paul Brook <paul@codesourcery.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>,
Carsten Otte <cotte@de.ibm.com>,
kvm@vger.kernel.org, Rusty Russell <rusty@rustcorp.com.au>,
virtualization@lists.linux-foundation.org,
Christian Borntraeger <borntraeger@de.ibm.com>,
Blue Swirl <blauwirbel@gmail.com>
Subject: Re: [Qemu-devel] [PATCH 05/11] qemu: MSI-X support functions
Date: Wed, 10 Jun 2009 15:07:34 +0100 [thread overview]
Message-ID: <200906101507.39823.paul@codesourcery.com> (raw)
In-Reply-To: <20090610094604.GD6844@redhat.com>
> > > Note that platform must set a flag to declare MSI supported.
> > > For PC this will be set by APIC.
> >
> > This sounds wrong. The device shouldn't know or care whether the system
> > has a MSI capable interrupt controller. That's for the guest OS to figure
> > out.
>
> You are right of course. In theory there's nothing that breaks if I
> set this flag to on, on all platforms. OTOH if qemu emulates some
> controller incorrectly, guest might misdetect MSI support in the
> controller, and things will break horribly.
>
> It seems safer to have a flag that can be enabled by people
> that know about a specific platform.
No. The solution is to fix whatever is broken.
If we really need to avoid MSI-X capable devices then that should be done
explicity per-device. i.e. you have a different virtio-net device that does
not use MSI-X.
Paul
WARNING: multiple messages have this Message-ID (diff)
From: Paul Brook <paul@codesourcery.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Carsten Otte <cotte@de.ibm.com>,
kvm@vger.kernel.org, Rusty Russell <rusty@rustcorp.com.au>,
qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org,
Blue Swirl <blauwirbel@gmail.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Avi Kivity <avi@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 05/11] qemu: MSI-X support functions
Date: Wed, 10 Jun 2009 15:07:34 +0100 [thread overview]
Message-ID: <200906101507.39823.paul@codesourcery.com> (raw)
In-Reply-To: <20090610094604.GD6844@redhat.com>
> > > Note that platform must set a flag to declare MSI supported.
> > > For PC this will be set by APIC.
> >
> > This sounds wrong. The device shouldn't know or care whether the system
> > has a MSI capable interrupt controller. That's for the guest OS to figure
> > out.
>
> You are right of course. In theory there's nothing that breaks if I
> set this flag to on, on all platforms. OTOH if qemu emulates some
> controller incorrectly, guest might misdetect MSI support in the
> controller, and things will break horribly.
>
> It seems safer to have a flag that can be enabled by people
> that know about a specific platform.
No. The solution is to fix whatever is broken.
If we really need to avoid MSI-X capable devices then that should be done
explicity per-device. i.e. you have a different virtio-net device that does
not use MSI-X.
Paul
next prev parent reply other threads:[~2009-06-10 14:07 UTC|newest]
Thread overview: 105+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1243253205.git.mst@redhat.com>
2009-05-25 12:12 ` [PATCHv2] qemu: make default_write_config use mask table Michael S. Tsirkin
2009-05-25 12:12 ` Michael S. Tsirkin
2009-05-25 12:12 ` [Qemu-devel] " Michael S. Tsirkin
2009-05-25 12:24 ` [PATCH 01/11] " Michael S. Tsirkin
2009-05-25 12:24 ` [Qemu-devel] " Michael S. Tsirkin
2009-05-25 12:24 ` Michael S. Tsirkin
2009-05-25 12:25 ` [PATCH 02/11] qemu: capability bits in pci save/restore Michael S. Tsirkin
2009-05-25 12:25 ` [Qemu-devel] " Michael S. Tsirkin
2009-05-25 12:25 ` Michael S. Tsirkin
2009-05-25 12:25 ` [PATCH 03/11] qemu: add routines to manage PCI capabilities Michael S. Tsirkin
2009-05-25 12:25 ` Michael S. Tsirkin
2009-05-25 12:25 ` [Qemu-devel] " Michael S. Tsirkin
2009-05-26 8:49 ` Isaku Yamahata
2009-05-26 8:49 ` Isaku Yamahata
2009-05-26 9:22 ` Michael S. Tsirkin
2009-05-26 9:22 ` Michael S. Tsirkin
2009-05-26 9:22 ` Michael S. Tsirkin
2009-05-26 8:49 ` Isaku Yamahata
2009-05-26 9:30 ` [PATCH] qemu: fix pci_find_capability for multiple caps Michael S. Tsirkin
2009-05-26 9:30 ` Michael S. Tsirkin
2009-05-26 9:30 ` [Qemu-devel] " Michael S. Tsirkin
2009-05-25 12:25 ` [PATCH 04/11] qemu: helper routines for pci access Michael S. Tsirkin
2009-05-25 12:25 ` Michael S. Tsirkin
2009-05-25 12:25 ` [Qemu-devel] " Michael S. Tsirkin
2009-05-26 2:33 ` Isaku Yamahata
2009-05-26 2:33 ` Isaku Yamahata
2009-05-26 6:41 ` Michael S. Tsirkin
2009-05-26 6:41 ` Michael S. Tsirkin
2009-05-26 8:07 ` Avi Kivity
2009-05-26 8:07 ` Avi Kivity
2009-05-26 8:49 ` Michael S. Tsirkin
2009-05-26 8:49 ` Michael S. Tsirkin
2009-05-26 8:49 ` Michael S. Tsirkin
2009-05-26 8:07 ` Avi Kivity
2009-05-26 6:41 ` Michael S. Tsirkin
2009-05-26 2:33 ` Isaku Yamahata
2009-05-25 12:25 ` [PATCH 05/11] qemu: MSI-X support functions Michael S. Tsirkin
2009-05-25 12:25 ` [Qemu-devel] " Michael S. Tsirkin
2009-06-09 23:19 ` Paul Brook
2009-06-09 23:19 ` Paul Brook
2009-06-10 9:46 ` Michael S. Tsirkin
2009-06-10 9:46 ` Michael S. Tsirkin
2009-06-10 9:46 ` Michael S. Tsirkin
2009-06-10 14:07 ` Paul Brook [this message]
2009-06-10 14:07 ` Paul Brook
2009-06-10 14:25 ` Michael S. Tsirkin
2009-06-10 14:25 ` Michael S. Tsirkin
2009-06-10 14:25 ` Michael S. Tsirkin
2009-06-10 14:39 ` Paul Brook
2009-06-10 14:39 ` Paul Brook
2009-06-10 14:47 ` Michael S. Tsirkin
2009-06-10 14:47 ` Michael S. Tsirkin
2009-06-10 14:47 ` Michael S. Tsirkin
2009-06-10 15:15 ` Paul Brook
2009-06-10 15:15 ` Paul Brook
2009-06-10 15:52 ` Michael S. Tsirkin
2009-06-10 15:52 ` Michael S. Tsirkin
2009-06-10 15:52 ` Michael S. Tsirkin
2009-06-10 16:08 ` Paul Brook
2009-06-10 16:08 ` Paul Brook
2009-06-10 16:26 ` Michael S. Tsirkin
2009-06-10 16:26 ` Michael S. Tsirkin
2009-06-10 16:46 ` Paul Brook
2009-06-10 16:46 ` Paul Brook
2009-06-10 17:03 ` Michael S. Tsirkin
2009-06-10 17:03 ` Michael S. Tsirkin
2009-06-10 17:30 ` Paul Brook
2009-06-10 17:30 ` Paul Brook
2009-06-10 17:30 ` Paul Brook
2009-06-10 18:07 ` Michael S. Tsirkin
2009-06-10 18:07 ` Michael S. Tsirkin
2009-06-10 18:07 ` Michael S. Tsirkin
2009-06-10 19:04 ` Paul Brook
2009-06-10 19:04 ` Paul Brook
2009-06-11 8:29 ` Michael S. Tsirkin
2009-06-11 8:29 ` Michael S. Tsirkin
2009-06-11 8:29 ` Michael S. Tsirkin
2009-06-10 19:04 ` Paul Brook
2009-06-10 17:03 ` Michael S. Tsirkin
2009-06-10 16:46 ` Paul Brook
2009-06-10 16:26 ` Michael S. Tsirkin
2009-06-10 16:08 ` Paul Brook
2009-06-10 15:15 ` Paul Brook
2009-06-10 14:39 ` Paul Brook
2009-06-10 14:07 ` Paul Brook
2009-06-09 23:19 ` Paul Brook
2009-05-25 12:25 ` Michael S. Tsirkin
2009-05-25 12:25 ` [PATCH 06/11] qemu: add flag to disable MSI-X by default Michael S. Tsirkin
2009-05-25 12:25 ` Michael S. Tsirkin
2009-05-25 12:25 ` [Qemu-devel] " Michael S. Tsirkin
2009-05-25 12:25 ` [PATCH 07/11] qemu: minimal MSI/MSI-X implementation for PC Michael S. Tsirkin
2009-05-25 12:25 ` [Qemu-devel] " Michael S. Tsirkin
2009-05-25 12:25 ` Michael S. Tsirkin
2009-05-25 12:26 ` [PATCH 08/11] qemu: add support for resizing regions Michael S. Tsirkin
2009-05-25 12:26 ` [Qemu-devel] " Michael S. Tsirkin
2009-05-25 12:26 ` Michael S. Tsirkin
2009-05-25 12:26 ` [PATCH 09/11] qemu: virtio support for many interrupt vectors Michael S. Tsirkin
2009-05-25 12:26 ` [Qemu-devel] " Michael S. Tsirkin
2009-05-25 12:26 ` Michael S. Tsirkin
2009-05-25 12:26 ` [PATCH 10/11] qemu: MSI-X support in virtio PCI Michael S. Tsirkin
2009-05-25 12:26 ` [Qemu-devel] " Michael S. Tsirkin
2009-05-25 12:26 ` Michael S. Tsirkin
2009-05-25 12:26 ` [PATCH 11/11] qemu: request 3 vectors in virtio-net Michael S. Tsirkin
2009-05-25 12:26 ` Michael S. Tsirkin
2009-05-25 12:26 ` [Qemu-devel] " Michael S. Tsirkin
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