The specification for VHOST_USER_ADD/REM_MEM_REG messages is unclear
in several points, which has led to clients having incompatible
implementations. This changes the specification to be more explicit
about them:

* VHOST_USER_ADD_MEM_REG is not specified as receiving a file
  descriptor, though it obviously does need to do so. All
  implementations agree on this one, fix the specification.

* VHOST_USER_REM_MEM_REG is not specified as receiving a file
  descriptor either, and it also has no reason to do so. rust-vmm does
  not send file descriptors for removing a memory region (in agreement
  with the specification), libvhost-user and QEMU do (which is a bug),
  though libvhost-user doesn't actually make any use of it.

  Change the specification so that for compatibility QEMU's behaviour
  becomes legal, even if discouraged, but rust-vmm's behaviour becomes
  the explicitly recommended mode of operation.

* VHOST_USER_ADD_MEM_REG doesn't have a documented return value, which
  is the desired behaviour in the non-postcopy case. It also implemented
  like this in QEMU and rust-vmm, though libvhost-user is buggy and
  sometimes sends an unexpected reply. This will be fixed in a separate
  patch.

  However, in postcopy mode it does reply like VHOST_USER_SET_MEM_TABLE.
  This behaviour is shared between libvhost-user and QEMU; rust-vmm
  doesn't implement postcopy mode yet. Mention it explicitly in the
  spec.

* The specification doesn't mention how VHOST_USER_REM_MEM_REG
  identifies the memory region to be removed. Change it to describe the
  existing behaviour of libvhost-user (guest address, user address and
  size must match).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20220407133657.155281-2-kwolf@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

we switched to front-end/back-end, but newer patches
reintroduced old language. Fix this up.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

This patch adds a get_vhost() callback function for VirtIODevices that
returns the device's corresponding vhost_dev structure, if the vhost
device is running. This patch also adds a vhost_started flag for
VirtIODevices.

Previously, a VirtIODevice wouldn't be able to tell if its corresponding
vhost device was active or not.

Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Message-Id: <1648819405-25696-3-git-send-email-jonah.palmer@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

This patch drops the name parameter for the virtio_init function.

The pair between the numeric device ID and the string device ID
(name) of a virtio device already exists, but not in a way that
lets us map between them.

This patch lets us do this and removes the need for the name
parameter in the virtio_init function.

Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Message-Id: <1648819405-25696-2-git-send-email-jonah.palmer@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

At a couple of hundred bytes per notifier allocating one for every
potential queue is very wasteful as most devices only have a few
queues. Instead of having this handled statically dynamically assign
them and track in a GPtrArray.

[AJB: it's hard to trigger the vhost notifiers code, I assume as it
requires a KVM guest with appropriate backend]

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220321153037.3622127-14-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Previously we would silently suppress VHOST_USER_PROTOCOL_F_CONFIG
during the protocol negotiation if the QEMU stub hadn't implemented
the vhost_dev_config_notifier. However this isn't the only way we can
handle config messages, the existing vdc->get/set_config can do this
as well.

Lightly re-factor the code to check for both potential methods and
instead of silently squashing the feature error out. It is unlikely
that a vhost-user backend expecting to handle CONFIG messages will
behave correctly if they never get sent.

Fixes: 1c3e5a26 ("vhost-user: back SET/GET_CONFIG requests with a protocol feature")
Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

Message-Id: <20220321153037.3622127-13-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

While trying to get my head around the nest of interactions for vhost
devices I though I could start by documenting the key API functions.
This patch documents the main API hooks for creating and starting a
vhost device as well as how the configuration changes are handled.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20220321153037.3622127-11-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

While writing my own VirtIO devices I've gotten confused with how
things are structured and what sort of shared infrastructure there is.
If we can document how everything is supposed to work we can then
maybe start cleaning up inconsistencies in the code.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20220309164929.19395-1-alex.bennee@linaro.org>

Message-Id: <20220321153037.3622127-10-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

This is useful for more human readable debug messages in vhost-user
programs.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220321153037.3622127-9-alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Make the language about feature negotiation explicitly clear about the
handling of the VHOST_USER_F_PROTOCOL_FEATURES feature bit. Try and
avoid the sort of bug introduced in vhost.rs REPLY_ACK processing:

  https://github.com/rust-vmm/vhost/pull/24



Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Jiang Liu <gerry@linux.alibaba.com>
Message-Id: <20210226111619.21178-1-alex.bennee@linaro.org>

Message-Id: <20220321153037.3622127-8-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

This matches the nomenclature that is generally used.  Also commonly used
is client/server, but it is not as clear because sometimes the front-end
exposes a passive (server) socket that the back-end connects to.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210226143413.188046-4-pbonzini@redhat.com>
Message-Id: <20220321153037.3622127-7-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

This section is using the word "back-end" to refer to the
"slave's back-end", and talking about the "client" for
what the rest of the document calls the "slave".

Rework it to free the use of the term "back-end", which in
the next patch will replace "slave".

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210226143413.188046-3-pbonzini@redhat.com>
Message-Id: <20220321153037.3622127-6-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

It is not necessary to mention which side is sending/receiving
each payload; it is more interesting to say which is the request
and which is the reply.  This also matches what vhost-user-gpu.rst
already does.

While at it, ensure that all messages list both the request and
the reply payload.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210226143413.188046-2-pbonzini@redhat.com>
Message-Id: <20220321153037.3622127-5-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

These are useful when trying to debug the initial vhost-user
negotiation, especially when it hard to get logging from the low level
library on the other side.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

Message-Id: <20220321153037.3622127-4-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200925125147.26943-6-alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220321153037.3622127-3-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

This allows other device classes that will be exposed via PCI to be
able to do so in the appropriate hw/ directory. I resisted the
temptation to re-order headers to be more aesthetically pleasing.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20200925125147.26943-4-alex.bennee@linaro.org>

Message-Id: <20220321153037.3622127-2-alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

"0x200000000" is much more readable than "8589934592".
The change saves one step (conversion) while debugging.

Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Message-Id: <20220318140440.596019-1-i.maximets@ovn.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

We need to update iq_dw according to the DMA_IRQ_REG during post
load. Otherwise we may get wrong IOTLB invalidation descriptor after
migration.

Fixes: fb43cf73 ("intel_iommu: scalable mode emulation")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220317080522.14621-2-jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>

We need check whether passthrough is enabled during
vtd_switch_address_space() by checking the context entries. This
requires the root_scalable to be set correctly otherwise we may try to
check legacy rsvd bits instead of scalable ones.

Fixing this by updating root_scalable before switching the address
spaces during post_load.

Fixes: fb43cf73 ("intel_iommu: scalable mode emulation")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220317080522.14621-1-jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>

According to vtd spec v3.3 3.14:

"""
Software must not program paging-structure entries to remap any
address to the interrupt address range. Untranslated requests and
translation requests that result in an address in the interrupt range
will be blocked with condition code LGN.4 or SGN.8.
"""

This patch blocks the request that result in interrupt address range.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220210092815.45174-2-jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>

This fault reason is not used and is duplicated with SPT.2 condition
code. So let's remove it.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220210092815.45174-1-jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>

We don't need to check kvm_enable_x2apic(). It's perfectly OK to support
interrupt remapping even if we can't address CPUs above 254. Kind of
pointless, but still functional.

The check on kvm_enable_x2apic() needs to happen *anyway* in order to
allow CPUs above 254 even without an IOMMU, so allow that to happen
elsewhere.

However, we do require the *split* irqchip in order to rewrite I/OAPIC
destinations. So fix that check while we're here.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Acked-by: Claudio Fontana <cfontana@suse.de>
Message-Id: <20220314142544.150555-4-dwmw2@infradead.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

We should probably check if we were meant to be exposing IR, before
letting the guest turn the IRE bit on.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220314142544.150555-3-dwmw2@infradead.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

By setting none of the SAGAW bits we can indicate to a guest that DMA
translation isn't supported. Tested by booting Windows 10, as well as
Linux guests with the fix at https://git.kernel.org/torvalds/c/c40aaaac10



Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220314142544.150555-2-dwmw2@infradead.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

The check on x86ms->apic_id_limit in pc_machine_done() had two problems.

Firstly, we need KVM to support the X2APIC API in order to allow IRQ
delivery to APICs >= 255. So we need to call/check kvm_enable_x2apic(),
which was done elsewhere in *some* cases but not all.

Secondly, microvm needs the same check. So move it from pc_machine_done()
to x86_cpus_init() where it will work for both.

The check in kvm_cpu_instance_init() is now redundant and can be dropped.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Acked-by: Claudio Fontana <cfontana@suse.de>
Message-Id: <20220314142544.150555-1-dwmw2@infradead.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Coverity rightly reports that is not free in that case.

Fixes: Coverity CID 1487559
Fixes: 100890f7 ("vhost: Shadow virtqueue buffers forwarding")

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20220512175747.142058-7-eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Per https://discourse.gnome.org/t/port-your-module-from-g-memdup-to-g-memdup2-now/5538



  The old API took the size of the memory to duplicate as a guint,
  whereas most memory functions take memory sizes as a gsize. This
  made it easy to accidentally pass a gsize to g_memdup(). For large
  values, that would lead to a silent truncation of the size from 64
  to 32 bits, and result in a heap area being returned which is
  significantly smaller than what the caller expects. This can likely
  be exploited in various modules to cause a heap buffer overflow.

Replace g_memdup() by the safer g_memdup2() wrapper.

Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20220512175747.142058-6-eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

With the introduction of MQ the index of the vq needs to be calculated
with the device model vq_index.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220512175747.142058-5-eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Fixes: 6d0b2226 ("vdpa: Adapt vhost_vdpa_get_vring_base to SVQ")

Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20220512175747.142058-4-eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Only the first one of them were properly enqueued back.

Fixes: 100890f7 ("vhost: Shadow virtqueue buffers forwarding")

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20220512175747.142058-3-eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

The device could have access to modify them, and it definitely have
access when we implement packed vq. Harden SVQ maintaining a private
copy of the descriptor chain. Other fields like buffer addresses are
already maintained sepparatedly.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20220512175747.142058-2-eperezma@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Provide an introduction to the main components of a CXL system,
with detailed explanation of memory interleaving, example command
lines and kernel configuration.

This was a challenging document to write due to the need to extract
only that subset of CXL information which is relevant to either
users of QEMU emulation of CXL or to those interested in the
implementation.  Much of CXL is concerned with specific elements of
the protocol, management of memory pooling etc which is simply
not relevant to what is currently planned for CXL emulation
in QEMU.  All comments welcome

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20220429144110.25167-43-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Add CXL Fixed Memory Windows to the CXL tests.

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Co-developed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20220429144110.25167-40-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Tables that differ from normal Q35 tables when running the CXL test.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20220429144110.25167-39-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

The DSDT includes several CXL specific elements and the CEDT
table is only present if we enable CXL.

The test exercises all current functionality with several
CFMWS, CHBS structures in CEDT and ACPI0016/ACPI00017 and _OSC
entries in DSDT.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20220429144110.25167-38-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Add exceptions for the DSDT and the new CEDT tables
specific to a new CXL test in the following patch.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20220429144110.25167-37-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Add the CFMWs memory regions to the memorymap and adjust the
PCI window to avoid hitting the same memory.

Signed-off-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Message-Id: <20220429144110.25167-36-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Add a trivial handler for now to cover the root bridge
where we could do some error checking in future.

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20220429144110.25167-35-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

These memops perform interleave decoding, walking down the
CXL topology from CFMWS described host interleave
decoder via CXL host bridge HDM decoders, through the CXL
root ports and finally call CXL type 3 specific read and write
functions.

Note that, whilst functional the current implementation does
not support:
* switches
* multiple HDM decoders at a given level.
* unaligned accesses across the interleave boundaries

Signed-off-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Message-Id: <20220429144110.25167-34-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Once a read or write reaches a CXL type 3 device, the HDM decoders
on the device are used to establish the Device Physical Address
which should be accessed.  These functions peform the required maths
and then use a device specific address space to access the
hostmem->mr to fullfil the actual operation.  Note that failed writes
are silent, but failed reads return poison.  Note this is based
loosely on:

https://lore.kernel.org/qemu-devel/20200817161853.593247-6-f4bug@amsat.org/


[RFC PATCH 0/9] hw/misc: Add support for interleaved memory accesses

Only lightly tested so far.  More complex test cases yet to be written.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20220429144110.25167-33-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>