From: Paul Brook <paul@codesourcery.com>
To: qemu-devel@nongnu.org
Cc: john cooper <john.cooper@redhat.com>,
Marc Haber <mh+qemu-devel@zugschlus.de>
Subject: Re: [Qemu-devel] virtio block device and sysfs
Date: Mon, 22 Mar 2010 15:14:48 +0000 [thread overview]
Message-ID: <201003221514.48811.paul@codesourcery.com> (raw)
In-Reply-To: <20100322123816.GF30984@torres.zugschlus.de>
> > John attempted this and it was reverted because the implementation
> > exhausted the PCI config space.
>
> I don't understand that. Existig hardware devices dump much more of
> their data such as vendor and model type information into the config
> space, how can using a field that real hardware uses exhaust the
> config space?
I think you (collectively) are confusing three different things:
- PCI config space: Not used in any significant way other than the standard
fields (i.e. basic device ID and configuring BARs). Slow/hard to access.
- PCI IO BAR: Used by virtio-pci devices to expose the virtio config space.
Extremely limited resource (max. 64k for the whole system). On real hardware
only really used for legacy interfaces because it's slow, cumbersome, and x86
specific. Unfortunately it currently seems to lower overhead than MMIO on KVM
:-(
- PCI MEM BAR (usually MMIO): How real devices expose themselves. Relatively
large address space (megabytes) available.
Paul
next prev parent reply other threads:[~2010-03-22 15:14 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-06 22:42 [Qemu-devel] virtio block device and sysfs Marc Haber
2010-03-09 1:17 ` jvrao
2010-03-09 8:21 ` Marc Haber
2010-03-09 20:04 ` jvrao
2010-03-09 20:06 ` jvrao
2010-03-09 21:15 ` Marc Haber
2010-03-09 21:34 ` Anthony Liguori
2010-03-21 16:16 ` Jamie Lokier
2010-03-22 6:26 ` john cooper
2010-03-22 12:42 ` Marc Haber
2010-03-22 14:59 ` john cooper
2010-03-25 5:30 ` john cooper
2010-06-29 18:15 ` Marc Haber
2010-06-29 18:03 ` john cooper
2010-06-29 20:20 ` Marc Haber
2010-06-29 18:33 ` Ryan Harper
2010-06-29 18:36 ` Marc Haber
2010-06-29 18:36 ` Marc Haber
2010-06-30 7:01 ` Markus Armbruster
2010-09-13 8:55 ` Marc Haber
2010-09-13 14:34 ` Ryan Harper
2010-09-14 7:43 ` Marc Haber
2011-03-10 12:14 ` Marc Haber
2010-03-22 12:38 ` Marc Haber
2010-03-22 14:22 ` john cooper
2010-03-22 16:24 ` Jamie Lokier
2010-03-22 16:33 ` john cooper
2010-04-22 20:30 ` Marc Haber
2010-04-22 20:48 ` john cooper
2010-03-22 15:14 ` Paul Brook [this message]
2010-04-22 20:33 ` Marc Haber
2010-03-22 14:46 ` [Qemu-devel] " Michael S. Tsirkin
2010-03-22 14:52 ` Anthony Liguori
2010-03-20 18:32 ` [Qemu-devel] " Richard W.M. Jones
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