From: "Michael S. Tsirkin" <mst@redhat.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>,
Sasha Levin <levinsasha928@gmail.com>,
Pawel Moll <pawel.moll@arm.com>,
virtualization <virtualization@lists.linux-foundation.org>
Subject: Re: [RFC 7/11] virtio_pci: new, capability-aware driver.
Date: Tue, 10 Jan 2012 19:03:36 +0200 [thread overview]
Message-ID: <20120110170334.GA18404@redhat.com> (raw)
In-Reply-To: <878vm6daqy.fsf@rustcorp.com.au>
On Wed, Dec 21, 2011 at 11:03:25AM +1030, Rusty Russell wrote:
> On Tue, 20 Dec 2011 13:37:18 +0200, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> > On Mon, Dec 19, 2011 at 09:38:42PM +1030, Rusty Russell wrote:
> > > On Mon, 19 Dec 2011 11:13:26 +0200, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> > >
> > > Actually, the host doesn't need anything, since it can always lock out
> > > the guest while it updates the area.
> > > It's the guest which can't do atomic updates.
> >
> > There are 2 cases
> > - updates by guest accesses by host
> > - accesses by guest updates by host
> >
> > Both are problematic because the guest accesses are split.
> > Consider the example I gave at the beginning was with capacity read
> > by guest. Host can not solve it without guest changes, right?
>
> Indeed, my brain fart. Let's pretend I didn't say that, and you didn't
> have to explain it to me in baby words :)
>
> > > > The counter can be in guest memory, right? So we don't pay extra
> > > > exits.
> > >
> > > Could be, but I'm not delighted about the design.
> >
> > OK, so this is an argument for always using a control vq, right?
>
> Yes. The idea that we can alter fields in the device-specific config
> area is flawed. There may be cases where it doesn't matter, but as an
> idea it was holed to begin with.
>
> We can reduce probability by doing a double read to check, but there are
> still cases where it will fail.
Okay - want me to propose an interface for that?
next prev parent reply other threads:[~2012-01-10 17:03 UTC|newest]
Thread overview: 101+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-08 10:22 [PATCH 0/11] RFC: PCI using capabilitities Rusty Russell
2011-12-08 10:30 ` [RFC 1/11] virtio: use u32, not bitmap for struct virtio_device's features Rusty Russell
2011-12-08 10:31 ` [RFC 2/11] virtio: add support for 64 bit features Rusty Russell
2011-12-08 10:32 ` [PATCH 0/11] RFC: PCI using capabilitities Sasha Levin
2011-12-08 10:32 ` [RFC 3/11] pci: add pci_iomap_range Rusty Russell
2011-12-15 8:30 ` Michael S. Tsirkin
2011-12-16 1:56 ` Rusty Russell
2011-12-08 10:34 ` [RFC 4/11] virtio-pci: define layout for virtio vendor-specific capabilities Rusty Russell
2011-12-10 21:14 ` Sasha Levin
2011-12-08 10:35 ` [RFC 6/11] virtio_pci: move old defines to legacy, introduce new structure Rusty Russell
2011-12-08 10:38 ` [RFC 6/11] virtio_pci: don't use the legacy driver if we find the new PCI capabilities Rusty Russell
2011-12-10 21:18 ` Sasha Levin
2011-12-11 5:15 ` Rusty Russell
2011-12-11 9:37 ` Michael S. Tsirkin
2011-12-08 10:39 ` [RFC 7/11] virtio_pci: new, capability-aware driver Rusty Russell
2011-12-11 9:42 ` Michael S. Tsirkin
2011-12-11 22:45 ` Rusty Russell
2011-12-12 11:49 ` Michael S. Tsirkin
2011-12-12 18:10 ` Don Dutile
2011-12-16 1:58 ` Rusty Russell
2013-05-28 7:56 ` Michael S. Tsirkin
2013-05-29 1:17 ` Rusty Russell
2013-05-29 10:21 ` Michael S. Tsirkin
2013-05-30 2:17 ` Rusty Russell
2011-12-12 18:25 ` Michael S. Tsirkin
2011-12-13 2:21 ` Rusty Russell
2011-12-15 8:27 ` Michael S. Tsirkin
2011-12-16 1:50 ` Rusty Russell
2011-12-18 10:18 ` Michael S. Tsirkin
2011-12-19 6:06 ` Rusty Russell
2011-12-19 9:13 ` Michael S. Tsirkin
2011-12-19 11:08 ` Rusty Russell
2011-12-20 11:37 ` Michael S. Tsirkin
2011-12-21 0:33 ` Rusty Russell
2011-12-21 9:19 ` Michael S. Tsirkin
2012-01-10 17:03 ` Michael S. Tsirkin [this message]
2012-01-11 0:25 ` Rusty Russell
2012-01-11 1:48 ` Benjamin Herrenschmidt
2012-01-11 8:47 ` Stefan Hajnoczi
2012-01-11 9:10 ` Benjamin Herrenschmidt
2012-01-11 14:28 ` Stefan Hajnoczi
2012-01-11 15:39 ` Michael S. Tsirkin
2012-01-11 17:21 ` Stefan Hajnoczi
2012-01-11 18:34 ` Michael S. Tsirkin
2012-01-11 20:56 ` Benjamin Herrenschmidt
2012-01-11 20:46 ` Benjamin Herrenschmidt
2012-01-12 10:37 ` Stefan Hajnoczi
2012-01-11 10:21 ` Michael S. Tsirkin
2012-01-11 21:13 ` Benjamin Herrenschmidt
2012-01-11 22:13 ` Michael S. Tsirkin
2012-01-11 22:19 ` Benjamin Herrenschmidt
2012-01-11 22:56 ` Benjamin Herrenschmidt
2012-01-12 5:29 ` Michael S. Tsirkin
2012-01-12 6:13 ` Benjamin Herrenschmidt
2012-01-12 6:37 ` Michael S. Tsirkin
2012-01-12 2:01 ` Rusty Russell
2012-01-12 4:31 ` Benjamin Herrenschmidt
2012-01-12 6:09 ` Michael S. Tsirkin
2012-01-12 6:28 ` Benjamin Herrenschmidt
2012-01-12 6:51 ` Michael S. Tsirkin
2012-01-12 7:03 ` Benjamin Herrenschmidt
2012-01-12 6:00 ` Michael S. Tsirkin
2012-01-13 3:22 ` Rusty Russell
2012-01-11 13:30 ` Anthony Liguori
2012-01-11 15:12 ` Michael S. Tsirkin
2012-01-11 15:15 ` Anthony Liguori
2012-01-11 15:21 ` Michael S. Tsirkin
2012-01-11 15:28 ` Anthony Liguori
2012-01-11 15:45 ` Michael S. Tsirkin
2012-01-11 16:02 ` Anthony Liguori
2012-01-11 17:08 ` Michael S. Tsirkin
2012-01-11 19:42 ` Anthony Liguori
2012-01-11 20:14 ` Michael S. Tsirkin
2012-01-11 20:26 ` Anthony Liguori
2012-01-11 21:02 ` Benjamin Herrenschmidt
2012-01-11 22:02 ` Michael S. Tsirkin
2012-01-11 22:16 ` Benjamin Herrenschmidt
2012-01-12 1:42 ` Rusty Russell
2012-01-13 2:19 ` Michael S. Tsirkin
2012-01-13 2:32 ` Benjamin Herrenschmidt
2012-01-18 15:29 ` Michael S. Tsirkin
2012-01-22 22:53 ` Rusty Russell
2012-01-18 4:52 ` Rusty Russell
2012-01-11 21:58 ` Michael S. Tsirkin
2012-01-11 20:59 ` Benjamin Herrenschmidt
2012-01-11 20:51 ` Benjamin Herrenschmidt
2012-01-11 20:50 ` Benjamin Herrenschmidt
2012-01-12 1:35 ` Rusty Russell
2011-12-08 10:40 ` [RFC 8/11] virtio_pci: share structure between legacy and modern Rusty Russell
2011-12-08 10:41 ` [RFC 9/11] virtio_pci: share interrupt/notify handlers " Rusty Russell
2011-12-08 10:42 ` [RFC 10/11] virtio_pci: share virtqueue setup/teardown between modern and legacy driver Rusty Russell
2011-12-08 10:44 ` [RFC 11/11] virtio_pci: simplify common helpers Rusty Russell
2011-12-08 15:37 ` [PATCH 0/11] RFC: PCI using capabilitities Sasha Levin
[not found] ` <1323358657.32487.9.camel@lappy>
2011-12-09 6:17 ` Rusty Russell
2011-12-10 21:32 ` Sasha Levin
2011-12-11 9:05 ` Avi Kivity
2011-12-11 10:03 ` Sasha Levin
2011-12-11 12:30 ` Michael S. Tsirkin
2011-12-11 12:48 ` Sasha Levin
2011-12-11 12:47 ` Michael S. Tsirkin
2011-12-11 12:53 ` Sasha Levin
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