Virtqueue notify is currently handled synchronously in userspace virtio. This
prevents the vcpu from executing guest code while hardware emulation code
handles the notify.
On systems that support KVM, the ioeventfd mechanism can be used to make
virtqueue notify a lightweight exit by deferring hardware emulation to the
iothread and allowing the VM to continue execution. This model is similar to
how vhost receives virtqueue notifies.
The result of this change is improved performance for userspace virtio devices.
Virtio-blk throughput increases especially for multithreaded scenarios and
virtio-net transmit throughput increases substantially.
Some virtio devices are known to have guest drivers which expect a notify to be
processed synchronously and spin waiting for completion.
For virtio-net, this also seems to interact with the guest stack in strange
ways so that TCP throughput for small message sizes (~200bytes)
is harmed. Only enable ioeventfd for virtio-blk for now.
Care must be taken not to interfere with vhost-net, which uses host
notifiers. If the set_host_notifier() API is used by a device
virtio-pci will disable virtio-ioeventfd and let the device deal with
host notifiers as it wishes.
Finally, there used to be a limit of 6 KVM io bus devices inside the
kernel. On such a kernel, don't use ioeventfd for virtqueue host
notification since the limit is reached too easily. This ensures that
existing vhost-net setups (which always use ioeventfd) have ioeventfds
available so they can continue to work.
After migration and on VM change state (running/paused) virtio-ioeventfd
will enable/disable itself.
* VIRTIO_CONFIG_S_DRIVER_OK -> enable virtio-ioeventfd
* !VIRTIO_CONFIG_S_DRIVER_OK -> disable virtio-ioeventfd
* virtio_pci_set_host_notifier() -> disable virtio-ioeventfd
* vm_change_state(running=0) -> disable virtio-ioeventfd
* vm_change_state(running=1) -> enable virtio-ioeventfd
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Move tracking vmstate change from virtio-net to virtio.c
as it is going to be used by virito-blk and virtio-pci
for the ioeventfd support.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
When migration triggers before a VQ is initialized,
base pa is 0 and last_used_index must be 0 too:
we don't have a ring to compare to.
Reported-by: Juan Quintela <quintela@redhat.com>
Tested-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit cd92f4cc22)
Checking available index upon load instead of
only when vm is running makes is easier to
debug failures.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
As status is set to 0 on reset, invoke the relevant callback. This makes
for a cleaner code in devices as they don't need to duplicate the code
in their reset routine, as well as excercises this path a little more.
In particular this makes it possible to unify
vhost-net handling code with the following patch.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This patch adds trace events for virtqueue operations including
adding/removing buffers, notifying the guest, and receiving a notify
from the guest.
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Separate the mapping of requests to host memory from the descriptor iteration.
The next patch will make use of it in a different context.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
After migration, vhost was not getting features
acked because set_features callback was never invoked.
The fix is just to invoke that callback.
Reported-by: David L Stevens <dlstevens@us.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: David L Stevens <dlstevens@us.ibm.com>
u_int64_t raises compiler error messages:
CC libhw32/virtio.o
/qemu/ar7/hw/virtio.c: In function ‘virtio_queue_get_avail_size’:
/qemu/ar7/hw/virtio.c:776: error: ‘u_int64_t’ undeclared (first use in this function)
/qemu/ar7/hw/virtio.c:776: error: (Each undeclared identifier is reported only once
/qemu/ar7/hw/virtio.c:776: error: for each function it appears in.)
Replacing u_int64_t by uint64_t helps.
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
vhost needs physical addresses for ring and other queue fields,
so add APIs for these. In particular, add binding API to set
host/guest notifiers. Will be used by vhost.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
VIRTIO_PCI_QUEUE_MAX is redefined in hw/virtio.c. Let's just keep it in
hw/virtio.h.
Also, bump up the value of the maximum allowed virtqueues to 64. This is
in preparation to allow multiple ports per virtio-console device.
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Add feature bits as properties to virtio. This makes it possible to e.g. define
machine without indirect buffer support, which is required for 0.10
compatibility, or without hardware checksum support, which is required for 0.11
compatibility. Since default values for optional features are now set by qdev,
get_features callback has been modified: it sets non-optional bits, and clears
bits not supported by host.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Rename features->guest_features. This is
what they are, avoid confusion with
host features which we also need to keep around.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
migrating between hosts which have different features
might break silently, if the migration destination
does not support some features supported by source.
Prevent this from happening by comparing acked feature
bits with the mask supported by the device.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
wmb must be at least a compiler barrier, even without SMP.
Further, we likely need some rmb()/mb() as well:
I have not audited the code but lguest has mb(),
add a comment for now.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
In the very least, a change like this requires discussion on the list.
The naming convention is goofy and it causes a massive merge problem. Something
like this _must_ be presented on the list first so people can provide input
and cope with it.
This reverts commit 99a0949b72.
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
initialize vectors for all vqs to VIRTIO_NO_VECTOR rather than 0 which
is a valid vector. This fixes migration which happened before driver
was loaded.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reported-by: Amit Shah <amit.shah@redhat.com>
Tested-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
control vector is saved/restored by virtio-pci,
it does not belong in virtio.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Implement bindings for virtio save/load. Use them in virtio pci.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Extend virtio to support many interrupt vectors, and rearrange code in
preparation for multi-vector support (mostly move reset out to bindings,
because we will have to reset the vectors in transport-specific code).
Actual bindings in pci, and use in net, to follow.
Load and save are not connected to bindings yet, so they are left
stubbed out for now.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Support a new feature flag for indirect ring entries. These are ring
entries which point to a table of buffer descriptors.
The idea here is to increase the ring capacity by allowing a larger
effective ring size whereby the ring size dictates the number of
requests that may be outstanding, rather than the size of those
requests.
This should be most effective in the case of block I/O where we can
potentially benefit by concurrently dispatching a large number of
large requests. Even in the simple case of single segment block
requests, this results in a threefold increase in ring capacity.
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Change the vring descriptor helpers to take the physical
address of the descriptor table rather than a virtqueue.
This is needed in order to allow these helpers to be used
with an indirect descriptor table.
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Add the parameter 'order' to qemu_register_reset and sort callbacks on
registration. On system reset, callbacks with lower order will be
invoked before those with higher order. Update all existing users to the
standard order 0.
Note: At least for x86, the existing users seem to assume that handlers
are called in their registration order. Therefore, the patch preserves
this property. If someone feels bored, (s)he could try to identify this
dependency and express it properly on callback registration.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
We're currently leaking memory and file descriptors on device
hot-unplug.
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7150 c046a42c-6fe2-441c-8c8c-71466251a162
I believe this is behind the following:
https://bugs.edge.launchpad.net/ubuntu/jaunty/+source/linux/+bug/331128
virtio_pci in 2.6.25 didn't do feature negotiation correctly: it acked every
bit. Fortunately, we can detect this.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6975 c046a42c-6fe2-441c-8c8c-71466251a162
There may be cases where the guest does not want the avail queue
interrupt, even when it's empty. For the virtio-net case, the
guest may use a different buffering scheme or decide polling for
used buffers is more efficient. This can be accomplished by simply
checking for whether the guest has acknowledged the existing notify
on empty flag.
Signed-off-by: Alex Williamson <alex.williamson@hp.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6865 c046a42c-6fe2-441c-8c8c-71466251a162
This patch adds and uses #defines for PCI device classes and subclases,
using a new pci_config_set_class() function, similar to the recently
added pci_config_set_vendor_id() and pci_config_set_device_id().
Change since v1: fixed compilation of hw/sun4u.c
Signed-off-by: Stuart Brady <stuart.brady@gmail.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6491 c046a42c-6fe2-441c-8c8c-71466251a162
Current Linux guests oops if the host notifies of a
config change before a driver has been bound to the
device.
It's pretty pointless for us to do notify of config
changes before status is S_DRIVER_OK anyway, so let's
just not do it.
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6471 c046a42c-6fe2-441c-8c8c-71466251a162
This patch defines PCI vendor and device IDs in pci.h (matching those
from Linux's pci_ids.h), and uses those definitions where appropriate.
Change from v1:
Introduces pci_config_set_vendor_id() / pci_config_set_device_id()
accessors as suggested by Anthony Liguori.
Signed-off-by: Stuart Brady <stuart.brady@gmail.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6442 c046a42c-6fe2-441c-8c8c-71466251a162
Fix compiler warning on OSX, reported by Andreas Faerber.
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5982 c046a42c-6fe2-441c-8c8c-71466251a162
Windows does not have sys/uio.h and does not have err.h.
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5877 c046a42c-6fe2-441c-8c8c-71466251a162
TARGET_PAGE_SIZE should only be used internal to qemu, not in guest/host
interfaces. The virtio frontend code in Linux uses two constants (PFN shift
and vring alignment) for the interface, so update qemu to match.
I've tested this with PowerPC KVM and confirmed that it fixes virtio problems
when using non-TARGET_PAGE_SIZE pages in the guest.
Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5871 c046a42c-6fe2-441c-8c8c-71466251a162
This patch adds core support for VirtIO. VirtIO is a paravirtualization
framework that has been in Linux since 2.6.21. A PCI transport has been
available since 2.6.25. Network drivers are also available for Windows.
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5869 c046a42c-6fe2-441c-8c8c-71466251a162
