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Resuming the effort to get the gpu device specs merged.
Support for 2d mode (3d/virgl mode is not covered by this patch) has
been added to the linux kernel version 4.2 and to qemu version 2.4.
git branch:
https://www.kraxel.org/cgit/virtio-spec/commit/?h=virtio-gpu
Rendered versions are available here:
https://www.kraxel.org/virtio/virtio-v1.0-cs03-virtio-gpu.pdf
https://www.kraxel.org/virtio/virtio-v1.0-cs03-virtio-gpu.html#x1-2800007
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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Allocate a feature bit for virtio devices which support SR-IOV.
Note: at proposer's request, driver requirements have been
omitted - a reworked version is now being discussed.
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/11
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
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There will be hardware virtio devices in the future, which
require drivers to use the barriers suitable for I/O devices,
compared with software virtio devices which just require
drivers to use the barriers suitable for CPU cores.
To fix the ordering issue for hardware virtio devices, add
a new feature: VIRTIO_F_IO_BARRIER. When negotiated, driver
will use the barriers suitable for I/O devices.
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/10
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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The Linux kernel exports the number of successful and failed
hugetlb page allocations via the virtio balloon driver. These
two counts need to be documented in this specification.
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/8
Signed-off-by: Jonathan Helman <jonathan.helman@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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This reverts commit 396b1957817e0bd14697e28d9fe61bfc80f1350f.
Was pushed by mistake.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Some devices benefit from ability to find out the number of available
descriptors in the ring: for efficiency or as a debugging aid.
To help with these optimizations, add a new feature:
VIRTIO_F_NOTIFICATION_DATA. When negotiated, driver notifications to the
device include this extra information.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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The flag VIRTIO_NET_HDR_F_DATA_VALID is aleady mentioned in the virtio-net
spec however it is not defined in the struct. This flag is already defined
and used in virtio-net device in Qemu as well as some of it's drivers.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/6
Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3182
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Linux kernel provides some balloon memory statistics that were not
included in the specs. Include them to avoid any ID clashes in the
future.
Signed-off-by: Tomáš Golembiovský <tgolembi@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/4
Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3180
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Existing virtio-blk protocol doesn't have DISCARD/WRITE ZEROES support,
this will impact the performance when using SSD backend over file systems.
Here is the proposal to extend existing virtio-blk protocol to support
DISCARD/WRITE ZEROES commands.
Basic idea here is using 16 Bytes payload to support 1 descriptor, users
can put several segments together with 1 DISCARD/WRITE ZEROES command.
struct virtio_blk_discard_write_zeroes {
le64 sector;
le32 num_sectors;
struct {
le32 unmap:1;
le32 reserved:31;
} flags;
};
For the purpose to support such feature, we need to introduce 2 new feature
flags: VIRTIO_BLK_F_DISCARD/VIRTIO_BLK_F_WRITE_ZEROES, and 2 new command
types: VIRTIO_BLK_T_DISCARD/VIRTIO_BLK_T_WRITE_ZEROES. Also we introduce
several new parameters in the configuration space of virtio-blk:
max_discard_sectors/max_discard_seg/max_write_zeroes_sectors.
These parameters will tell the OS what's the granularity when
issuing such commands.
If both DISCARD and WRITE ZEROES are supported, unmap flag bit maybe used
for WRITE ZEROES command with DISCARD bit enabled.
Signed-off-by: Changpeng Liu <changpeng.liu@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3181
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/5
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Using descriptors in-order is sometimes beneficial. Add an option for
that - per-format detail allowing more optimizations will be added by
follow-up patches.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3177
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/3
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Performance analysis of this is in my kvm forum 2016 presentation. The
idea is to have a r/w descriptor in a ring structure, replacing the used
and available ring, index and descriptor buffer.
This is also easier for devices to implement than the 1.0 layout.
Several more enhancements will be necessary to actually make this
efficient for devices to use.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3177
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/3
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Update generic text to talk about available/used buffers, not rings.
Move some split-ring specific text to the correct section.
Update conformance section with link to the new conformance clause.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3177
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/3
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3177
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/3
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Replace descriptor table/available ring/used ring
with descriptor area/driver area/device area
in all transports.
Document what's in which area.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3177
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/3
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Document buffer used len and use that terminology everywhere in the
generic section.
Further, drop the 'used ring' terminology and just say virtqueue.
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3177
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/3
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virtqueue operation description is specific to the virtqueue
format. Move it out to split-ring.tex and update all
references.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3177
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/3
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Will be easier to manage this way.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3177
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/3
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3177
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/3
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Fixes: VIRTIO-155
Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3118
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Reserve device ID 23 for virtio-iommu devices.
Resolved VIRTIO-162
Approved https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3155
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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VIRTIO-84 added a requirement that each buffer is > header size but
there's no reason to require that for merge-able buffers since data can
be placed in follow-up buffers.
The current wording seems confusing enough that it seems likely
no one relies on this.
VIRTIO-159
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <1490654778-11857-1-git-send-email-mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
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The idea behind mergeable buffers was to simply use them in a way
similar to a chain of descriptors. Unfortunately the current text does
not say so - apparently nothing says device can't spread a packet over
as many buffers as it likes - but this didn't prevent drivers from
relying on buffers being used as a chain of descriptors, completely -
and blindly accessing it without checking the length at least for the
packet header.
Let's just make the spec match this reality - if devices ever want more
flexibility, we can add a feature bit.
Further, correct all misuses of a "descriptor" to "buffer" as that
is the entity that is being merged.
VIRTIO-160
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <1490655576-12173-1-git-send-email-mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
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receiveq(n) is at position 2(n-1), not 2n. Same error for transmitq(n)
and controlq.
VIRTIO-161
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
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On most virtio systems, physical addresses are provided from the driver
to the device and subsequently used to access memory directly. However,
some systems feature an IOMMU that complicates things slightly:
- The IOMMU might require configuration for DMA to work at all. Once
configured, the driver must pass bus addresses to the device, which
are then translated by the IOMMU into physical addresses in memory.
- The IOMMU might be bypassed by virtio DMA. In this case, physical
addresses must still be provided to the device by the driver, even
though an IOMMU appears to be present.
This has been solved by the addition of a new reserved feature bit,
VIRTIO_F_IOMMU_PLATFORM, to describe the two cases above. Legacy systems
will not negotiate the feature, and therefore continue to operate
directly on physical addresses.
VIRTIO-154
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/trunk@587 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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It is helpful for a host to indicate it's MTU to be set on guest NICs
other than the assumed 1500 byte value. This helps in situations where
the host network is using Jumbo Frames, or aiding in PMTU discovery by
configuring a homogenous network. It is also helpful for sizing receive
buffers correctly.
The change adds a new field to configuration area of network
devices. It will be used to pass a maximum MTU from the device to
the driver. This will be used by the driver as a maximum value for
packet sizes during transmission, without segmentation offloading.
In addition, in order to support backward and forward compatibility,
we introduce a new feature bit called VIRTIO_NET_F_MTU.
VIRTIO-152
Signed-off-by: Aaron Conole <aconole@redhat.com>
Cc: Victor Kaplansky <victork@redhat.com>
Reviewed-by: Hannes Reiencke <hare@suse.de>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/trunk@585 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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This patch just reserve next available device ID for pstore device
type. The device specification for pstore will come later.
VIRTIO-150
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Message-Id: <1468941217-12904-1-git-send-email-namhyung@gmail.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/trunk@583 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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VIRTIO-149
Signed-off-by: Christian Pinto <c.pinto@virtualopensystems.com>
Signed-off-by: Baptiste Reynal <b.reynal@virtualopensystems.com>
Message-Id: <1467111824-11548-2-git-send-email-c.pinto@virtualopensystems.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/trunk@582 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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Reserve a device ID for virtio crypto device to
avoid collisions with other new virtio devices.
Because 19 had been reserved for virtio socket
device, I'd like to reserve 20 for crypto device.
VIRTIO-148
Suggested-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Message-Id: <1460685060-5904-1-git-send-email-arei.gonglei@huawei.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/trunk@581 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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Add a device ID for the Socket device. The draft specification is
currently under review but it helps to reserve the ID to avoid
collisions with other new virtio devices.
VIRTIO-147
Suggested-by: Ian Campbell <ian.campbell@docker.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <1458729661-7514-1-git-send-email-stefanha@redhat.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/trunk@580 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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ccw currently allows the driver to update the status via the
CCW_CMD_WRITE_STATUS command; however, it does not allow the driver to
retrieve the current status at the device, which is needed to properly
support DEVICE_NEEDS_RESET.
Therefore, provide a new command CCW_CMD_READ_STATUS allowing the driver
to retrieve the device status. Provide this command when revision 2 has
been negotiated.
VIRTIO-117
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Message-Id: <1445243513-2263-2-git-send-email-cornelia.huck@de.ibm.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/trunk@579 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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Status bit order is inconsistent: they are neither in increasing
order nor in the order they are likely to be used.
The second approach seems more useful since there aren't
that many bits, so the numerical order does not help much.
A typical order of use would be:
ACKNOWLEDGE
DRIVER
then either FAILED or FEATURES_OK
then either FAILED or DRIVER_OK
then DEVICE_NEEDS_RESET (if device detects an error)
Sort the bits accordingly.
Reported-by: Kevin Lo <kevlo@kevlo.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@559 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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Since vring* and VRING* have been replaced with virtq* and VIRTQ*
respectively, rename the header virtio_ring.h to virtio_queue.h.
Suggested-by: Kevin Lo <kevlo@kevlo.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@558 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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The changes are not just to remove Linux assumptions,
we have also renamed ring->queue.
Tweak the header description accordingly.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@555 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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Current text says:
The legacy driver only presented num_buffers in the struct
virtio_net_hdr when VIRTIO_NET_F_MRG_RXBUF was not negotiated;
Should be:
"... was negotiated ..." instead of "... was not negotiated ..."
To be consistent with the following:
without that feature the structure was 2 bytes shorter.
Reported-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@554 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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The point of the configuration access capability is to enable
access to other capabilities. The intent never was to allow
writes to a random place within device BARs.
Limiting drivers simplifies devices - and devices can always
add another capability if drivers ever want to access
some other range.
This resolves VIRTIO-145.
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Accepted by electronic ballot:
https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=2865
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@547 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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VIRTIO_BLK_F_CONFIG_WCE is important in order to achieve good performance
(up to 2x, though more realistically +30-40%) in latency-bound workloads.
However, it was removed by mistake together with VIRTIO_BLK_F_FLUSH.
In addition, even removing VIRTIO_BLK_F_FLUSH was probably not a great
idea, because it simplifies simple drivers (e.g. firmware) that are okay
with a writethrough cache but still need data to persist after power loss.
What really should have been removed is just the possibility that devices
not propose VIRTIO_BLK_F_FLUSH, but even that only deserves a "SHOULD" in
the new world of conformance statements.
Restore these, with the following changes:
* clarify and use conformance statements in order to define writeback
and writethrough caching according to what is commonly done by high-end
storage.
* clarify (with conformance statements) the influence of the
VIRTIO_BLK_F_FLUSH feature on caching and how to proceed if only one of
VIRTIO_BLK_F_FLUSH and VIRTIO_BLK_F_CONFIG_WCE is negotiated.
* strengthen the requirement for persisting writes to MUST after
a VIRTIO_BLK_T_FLUSH request (and in other cases too involving the
new features).
The suggested behavior upon feature negotiation is okay for the Linux
implementation of virtio1, even after the implementation is modified to
support the two new features.
This fixes VIRTIO-144.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Accepted by electronic ballot:
https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=2864
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@546 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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This is a simple non-material change.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@542 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@541 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@540 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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\\note just before start of subsection seems to
confuse latex, resulting in incorrect text alignment.
Replace with \begin{note} \end{note}.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@532 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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VIRTIO-124
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@529 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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Fix up multiple issues in xmit/receive sections:
- drop MAY/MUST/SHOULD outside normative statements
- spell out conformance requirements for both drivers and
devices, for xmit and receive paths
- document the missing VIRTIO_NET_HDR_F_DATA_VALID
- document handling of unrecognized flag bits so we can extend
flags in the future, similar to VIRTIO_NET_HDR_F_DATA_VALID
VIRTIO-123
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@528 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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Document the new option, and also clarify behaviour
without it.
In particular, I noticed that actual field is not the
actual number of pages in the balloon as
driver might do inflate followed by deflate.
Also, device isn't always driven by interrupts,
driver can inflate/deflate in response to e.g.
memory compaction.
VIRTIO-126
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@527 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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Virtio 1.0 cs02 doesn't include a modern balloon device. At some
point we'll likely define an incompatible interface with a
different ID and different semantics. But for now, it's not a
big effort to support a transitional balloon device: this has the
advantage of supporting existing drivers, transparently, as well
as transports that don't allow mixing virtio 0 and virtio 1
devices. And balloon is an easy device to test, so it's also
useful for people to test virtio core handling of transitional
devices.
Three issues with legacy hypervisors have been identified:
1. Actual value is actually used, and is necessary for management
to work. Luckily 4 byte config space writes are now atomic.
When using old guests, hypervisors can detect access to the last byte.
When using old hypervisors, drivers can use atomic 4-byte accesses.
2. Hypervisors actually didn't ignore the stats from the first
buffer supplied. This means the values there would be
incorrect until hypervisor resends the request.
Add a note suggesting hypervisors ignore the 1st buffer.
3. QEMU simply over-writes stats from each buffer it gets.
Thus if driver supplies a different subset of stats
on each request, stale values will be there.
Require drivers to supply the same subset on each
request. This also gives us a simple way to figure out
which stats are supported.
VIRTIO-143
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@526 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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The driver MUST examine the length written by the driver
makes no sense. length is written by the device.
VIRTIO-142
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@523 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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many hypervisors implemented len field incorrectly.
Document existing bugs in the legacy sections.
VIRTIO-141
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@522 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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1) It's implied that a chain terminates with an indirect descriptor (since
VIRTIO-15) but we didn't spell out that a device MUST NOT continue it.
2) We allow [direct]->[direct]->[indirect], and qemu and bhyve both accept
it. Make it clear that this is valid, thus devices MUST handle it.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@521 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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MUST shouldn't be used outside normative statements,
that's confusing. Replace with "has to".
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@509 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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pci spec says what width access to use for 32, 16 and 8
bit fields, but does not explicitly say what to do for
32 bit fields. As we have text that says driver must
treat 64 bit accesses as non-atomic, this seems
to imply driver should always do two 32 bit wide accesses.
Let's make this an explicit requirement, and require
devices to support this.
VIRTIO-139
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@508 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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latexdiff doesn't handle changing labels well,
causes latex unresolved reference errors.
opencode and mark up diff manually.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@507 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
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