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2008-02-04virtio: balloon driverRusty Russell
After discussions with Anthony Liguori, it seems that the virtio balloon can be made even simpler. Here's my attempt. The device configuration tells the driver how much memory it should take from the guest (ie. balloon size). The guest feeds the page numbers it has taken via one virtqueue. A second virtqueue feeds the page numbers the driver wants back: if the device has the VIRTIO_BALLOON_F_MUST_TELL_HOST bit, then this queue is compulsory, otherwise it's advisory (and the guest can simply fault the pages back in). This driver can be enhanced later to deflate the balloon via a shrinker, oom callback or we could even go for a complete set of in-guest regulators. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-02-04virtio: Use PCI revision field to indicate virtio PCI ABI versionAnthony Liguori
As Avi pointed out, as we continue to massage the virtio PCI ABI, we can make things a little more friendly to users by utilizing the PCI revision field to indicate which version of the ABI we're using. This is a hard ABI version and incrementing it will cause the guest driver to break. This is the necessary changes to virtio_pci to support this. Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-02-04virtio: PCI deviceAnthony Liguori
This is a PCI device that implements a transport for virtio. It allows virtio devices to be used by QEMU based VMMs like KVM or Xen. Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-02-04virtio: Allow virtio to be modular and used by modulesRusty Russell
This is needed for the virtio PCI device to be compiled as a module. Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-02-04virtio: Use the sg_phys convenience function.Rusty Russell
Simple cleanup. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-02-04virtio: handle interrupts after callbacks turned offRusty Russell
Anthony Liguori found double interrupt suppression in the virtio_net driver, triggered by two skb_recv_done's in a row. This is because virtio_ring's interrupt suppression is a best-effort optimization: it contains no synchronization so the host can miss it and still send interrupts. But it's certainly nicer for virtio users if calling disable_cb actually disables callbacks, so we check for the race in the interrupt routine. Note: SMP guests might require syncronization here, but since disable_cb is actually called from interrupt context, there has to be some form of synchronization before the next same interrupt handler is called (Linux guarantees that the same device's irq handler will never run simultanously on multiple CPUs). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-02-04virtio: reset functionRusty Russell
A reset function solves three problems: 1) It allows us to renegotiate features, eg. if we want to upgrade a guest driver without rebooting the guest. 2) It gives us a clean way of shutting down virtqueues: after a reset, we know that the buffers won't be used by the host, and 3) It helps the guest recover from messed-up drivers. So we remove the ->shutdown hook, and the only way we now remove feature bits is via reset. We leave it to the driver to do the reset before it deletes queues: the balloon driver, for example, needs to chat to the host in its remove function. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-02-04virtio: clarify NO_NOTIFY flag usageRusty Russell
The other side (host) can set the NO_NOTIFY flag as an optimization, to say "no need to kick me when you add things". Make it clear that this is advisory only; especially that we should always notify when the ring is full. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-02-04virtio: explicit enable_cb/disable_cb rather than callback return.Rusty Russell
It seems that virtio_net wants to disable callbacks (interrupts) before calling netif_rx_schedule(), so we can't use the return value to do so. Rename "restart" to "cb_enable" and introduce "cb_disable" hook: callback now returns void, rather than a boolean. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-02-04virtio: simplify config mechanism.Rusty Russell
Previously we used a type/len pair within the config space, but this seems overkill. We now simply define a structure which represents the layout in the config space: the config space can now only be extended at the end. The main driver-visible changes: 1) We indicate what fields are present with an explicit feature bit. 2) Virtqueues are explicitly numbered, and not in the config space. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2007-11-19virtio: fix module/device unloadingRusty Russell
The virtio code never hooked through the ->remove callback. Although noone supports device removal at the moment, this code is already needed for module unloading. This of course also revealed bugs in virtio_blk, virtio_net and lguest unloading paths. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2007-11-12virtio: Force use of power-of-two for descriptor ring sizesRusty Russell
The virtio descriptor rings of size N-1 were nicely set up to be aligned to an N-byte boundary. But as Anthony Liguori points out, the free-running indices used by virtio require that the sizes be a power of 2, otherwise we get problems on wrap (demonstrated with lguest). So we replace the clever "2^n-1" scheme with a simple "align to page boundary" scheme: this means that all virtio rings take at least two pages, but it's safer than guessing cache alignment. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2007-11-12virtio: Fix used_idx wrap-aroundAnthony Liguori
The more_used() function compares the vq->vring.used->idx with last_used_idx. Since vq->vring.used->idx is a 16-bit integer, and last_used_idx is an unsigned int, this results in unpredictable behavior when vq->vring.used->idx wraps around. This patch corrects this by changing last_used_idx to the correct type. Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2007-10-23Virtio helper routines for a descriptor ringbuffer implementationRusty Russell
These helper routines supply most of the virtqueue_ops for hypervisors which want to use a ring for virtio. Unlike the previous lguest implementation: 1) The rings are variable sized (2^n-1 elements). 2) They have an unfortunate limit of 65535 bytes per sg element. 3) The page numbers are always 64 bit (PAE anyone?) 4) They no longer place used[] on a separate page, just a separate cacheline. 5) We do a modulo on a variable. We could be tricky if we cared. 6) Interrupts and notifies are suppressed using flags within the rings. Users need only get the ring pages and provide a notify hook (KVM wants the guest to allocate the rings, lguest does it sanely). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Dor Laor <dor.laor@qumranet.com>
2007-10-23Module autoprobing support for virtio drivers.Rusty Russell
This adds the logic to convert the virtio ids into module aliases, and includes a modalias entry in sysfs and the env var to make probing work. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2007-10-23Virtio interfaceRusty Russell
This attempts to implement a "virtual I/O" layer which should allow common drivers to be efficiently used across most virtual I/O mechanisms. It will no-doubt need further enhancement. The virtio drivers add buffers to virtio queues; as the buffers are consumed the driver "interrupt" callbacks are invoked. There is also a generic implementation of config space which drivers can query to get setup information from the host. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Dor Laor <dor.laor@qumranet.com> Cc: Arnd Bergmann <arnd@arndb.de>