[PATCH] kvm: qemu: virtio: enable VIRTIO_ZERO_COPY

[Mark McLoughlin <markmc@redhat.com>]

On Wed, 2008-12-03 at 11:27 -0600, Anthony Liguori wrote:
> In the absence of a zero-copy API, we cannot touch physical memory directly.
> This patch introduces a #define to control whether we touch buffers directly,
> or bounce the buffers through cpu_physical_memory_rw.
> 
> The #define is needed for merging virtio into upstream QEMU since zero-copy will
> not be accepted as-is.  As a bonus, I also added physical memory dirtying
> support to the zero-copy case so now live migration should work when using
> virtio.
> 
> With this patch, virtio is mergable into upstream QEMU (except for virtio-net,
> that's a different series though).
> 
> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
> 
> diff --git a/qemu/hw/virtio.c b/qemu/hw/virtio.c
> index 1a58940..9396580 100644
> --- a/qemu/hw/virtio.c
> +++ b/qemu/hw/virtio.c
> @@ -17,6 +17,8 @@
>  #include "virtio.h"
>  #include "sysemu.h"
>  
> +//#define VIRTIO_ZERO_COPY
> +

From: Mark McLoughlin <markmc@redhat.com>
Subject: [PATCH] kvm: qemu: virtio: enable VIRTIO_ZERO_COPY

Anthony intended to enable VIRTIO_ZERO_COPY before submitting,
so do that now.

Fixes an oops in the bounce buffer malloc in virtqueue_pop()
I have seen twice so far. We still need to track this down,
but it's very hard to reproduce.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
---
 qemu/hw/virtio.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/qemu/hw/virtio.c b/qemu/hw/virtio.c
index 16356e8..1d06fcc 100644
--- a/qemu/hw/virtio.c
+++ b/qemu/hw/virtio.c
@@ -16,7 +16,7 @@
 #include "virtio.h"
 #include "sysemu.h"
 
-//#define VIRTIO_ZERO_COPY
+#define VIRTIO_ZERO_COPY
 
 /* from Linux's linux/virtio_pci.h */
 
-- 
1.5.4.3