Am Montag 18 Mai 2009 16:26:15 schrieb Avi Kivity:
> Christian Borntraeger wrote:
> > Sorry for the late question, but I missed your first version. Is there a
> > way to change that code to use virtio instead of PCI? That would allow us
> > to use this driver on s390 and maybe other virtio transports.
>
> Opinion differs. See the discussion in
> http://article.gmane.org/gmane.comp.emulators.kvm.devel/30119.
>
> To summarize, Anthony thinks it should use virtio, while I believe
> virtio is useful for exporting guest memory, not for importing host memory.
I think the current virtio interface is not ideal for importing host memory,
but we can change that. If you look at the dcssblk driver for s390, it allows
a guest to map shared memory segments via a diagnose (hypercall). This driver
uses PCI regions to map memory.
My point is, that the method to map memory is completely irrelevant, we just
need something like mmap/shmget between the guest and the host. We could
define an interface in virtio, that can be used by any transport. In case of
pci this could be a simple pci map operation.
What do you think about something like: (CCed Rusty)
---
include/linux/virtio.h | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
Index: linux-2.6/include/linux/virtio.h
===================================================================
--- linux-2.6.orig/include/linux/virtio.h
+++ linux-2.6/include/linux/virtio.h
@@ -71,6 +71,31 @@ struct virtqueue_ops {
};
/**
+ * virtio_device_ops - operations for virtio devices
+ * @map_region: map host buffer at a given address
+ * vdev: the struct virtio_device we're talking about.
+ * addr: The address where the buffer should be mapped (hint only)
+ * length: THe length of the mapping
+ * identifier: the token that identifies the host buffer
+ * Returns the mapping address or an error pointer.
+ * @unmap_region: unmap host buffer from the address
+ * vdev: the struct virtio_device we're talking about.
+ * addr: The address where the buffer is mapped
+ * Returns 0 on success or an error
+ *
+ * TBD, we might need query etc.
+ */
+struct virtio_device_ops {
+ void * (*map_region)(struct virtio_device *vdev,
+ void *addr,
+ size_t length,
+ int identifier);
+ int (*unmap_region)(struct virtio_device *vdev, void *addr);
+/* we might need query region and other stuff */
+};
+
+
+/**
* virtio_device - representation of a device using virtio
* @index: unique position on the virtio bus
* @dev: underlying device.
@@ -85,6 +110,7 @@ struct virtio_device
struct device dev;
struct virtio_device_id id;
struct virtio_config_ops *config;
+ struct virtio_device_ops *ops;
/* Note that this is a Linux set_bit-style bitmap. */
unsigned long features[1];
void *priv;
--
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