From: "Michael S. Tsirkin" <mst@redhat.com>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
virtualization@lists.linux-foundation.org,
habanero@linux.vnet.ibm.com, Shirley Ma <mashirle@us.ibm.com>,
Krishna Kumar2 <krkumar2@in.ibm.com>,
kvm@vger.kernel.org, steved@us.ibm.com,
Tom Lendacky <tahm@linux.vnet.ibm.com>,
borntraeger@de.ibm.com, avi@redhat.com,
bryanv@daemoninthecloset.org
Subject: Re: [PATCHv3] virtio-spec: 64 bit features, used/avail event, fixes
Date: Wed, 3 Aug 2011 19:29:55 +0300 [thread overview]
Message-ID: <20110803162955.GA16768@redhat.com> (raw)
In-Reply-To: <4E397425.90808@redhat.com>
On Wed, Aug 03, 2011 at 06:15:33PM +0200, Gerd Hoffmann wrote:
> Hi,
>
> >E.g. with 32 bridges, and 32 devices behind each one,
> >the available 64K space gets us only 64 bytes per device.
>
> 15 bridges (with io window enabled) max, the smallest io window you
> can assign to a bridge is 4k,
Hmm true, I missed that. So with 32 devs we get 256 bytes per device.
We can still get low on that space when using
multifunction devices though (there could be up to 256 functions behind
a bridge, which only leaves 16 bytes per device).
BTW, this limitation will be a problem for pci express
devices.
> and you need some space for the
> devices on the root bus ...
>
> cheers,
> Gerd
next prev parent reply other threads:[~2011-08-03 16:30 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-01 10:25 [PATCHv3] virtio-spec: 64 bit features, used/avail event, fixes Michael S. Tsirkin
2011-06-02 1:49 ` Rusty Russell
2011-08-03 16:05 ` Michael S. Tsirkin
2011-08-03 16:15 ` Gerd Hoffmann
2011-08-03 16:29 ` Michael S. Tsirkin [this message]
2011-08-03 16:39 ` Michael S. Tsirkin
2011-08-04 7:55 ` Gerd Hoffmann
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