Allow a user to add a virtio-rng-pci (an emulated hardware random
number generator) to a VM with the rng0 setting. The setting is
version_guard()-ed.
Limit the selection of entropy source to one of three:
/dev/urandom (preferred): Non-blocking kernel entropy source
/dev/random: Blocking kernel source
/dev/hwrng: Hardware RNG on the host for passthrough
QEMU itself defaults to /dev/urandom (or the equivalent getrandom()
call) if no source file is given, but I don't fully trust that
behaviour to stay constant, considering the documentation [0] already
disagrees with the code [1], so let's always specify the file ourselves.
/dev/urandom is preferred, since it prevents host entropy starvation.
The quality of randomness is still good enough to emulate a hwrng, since
a) it's still seeded from the kernel's true entropy pool periodically
and b) it's mixed with true entropy in the guest as well.
Additionally, all sources about entropy predicition attacks I could find
mention that to predict /dev/urandom results, /dev/random has to be
accessed or manipulated in one way or the other - this is not possible
from a VM however, as the entropy we're talking about comes from the
*hosts* blocking pool.
More about the entropy and security implications of the non-blocking
interface in [2] and [3].
Note further that only one /dev/hwrng exists at any given time, if
multiple RNGs are available, only the one selected in
'/sys/devices/virtual/misc/hw_random/rng_current' will feed the file.
Selecting this is left as an exercise to the user, if at all required.
We limit the available entropy to 1 KiB/s by default, but allow the user
to override this. Interesting to note is that the limiter does not work
linearly, i.e. max_bytes=1024/period=1000 means that up to 1 KiB of data
becomes available on a 1000 millisecond timer, not that 1 KiB is
streamed to the guest over the course of one second - hence the
configurable period.
The default used here is the same as given in the QEMU documentation [0]
and has been verified to affect entropy availability in a guest by
measuring /dev/random throughput. 1 KiB/s is enough to avoid any
early-boot entropy shortages, and already has a significant impact on
/dev/random availability in the guest.
[0] https://wiki.qemu.org/Features/VirtIORNG
[1] https://git.qemu.org/?p=qemu.git;a=blob;f=crypto/random-platform.c;h=f92f96987d7d262047c7604b169a7fdf11236107;hb=HEAD
[2] https://lwn.net/Articles/261804/
[3] https://lwn.net/Articles/808575/
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
to achieve this we have to add 3 new scsihw addresses since lsi
controllers can only hold 7 scsi drives
we go up to 31, since this is the limit for virtio-scsi-single devices
we have reserved (we can increase this in the future)
to make it more future proof, we add a new pci bridge under pci
bridge 1, so we have to adapt the bridge adding code (we did not
need this for q35 previously)
impact on live migration:
since on older versions of qemu-server we do not have those config
settings, there is no problem from old -> new
new->old is not supported anyway and this breaks so that
the vm crashes and loses the configs for scsi15-30
(same behaviour as e.g. with audio0 and migration from new->old)
tested with 31 scsi disk on
i440fx + virtio-scsi
i440fx + lsi
q35 + virtio-scsi
q35 + lsi
with ovmf + seabios
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
For non pci express passthrough additional addresses are reserved.
For pcie passthrough pcie root ports are needed (unless guest is like
windows 7).
The first 4 pcie root ports are defined by default in the pve-q35*.cfg
files. If more than 4 pcie devices are passed through the needed root
ports are created on demand. This helps to keep live migration possible
without adding a new pve-q35*.cfg file.
For the windows 7 like guests additional addresses are reserved as well.
Signed-off-by: Aaron Lauterer <a.lauterer@proxmox.com>
with such a shared memory device, a vm can share data with other
vms or with the host via memory
one of the use cases is looking-glass[1] with pci-passthrough, which copies
the guest fb to the host and you get a high-speed, low-latency
display client for the vm
on vm stop we delete the file again
1: https://looking-glass.hostfission.com/
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
Win7 is very picky about pcie assignments and fails with
'error 12' the way we add hospci devices.
To combat that, we simply give the hostpci device a normal port
instead.
Start with address 0x10, so that we have space before those devices,
and between them and the ones configured in pve-q35.cfg should we
need it in the future.
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
On arm we start off with a pcie bridge pcie.0. We need a
keyboard in addition to the tablet device, and we need to
connect both to an 'ehci' controller.
To do all this, we also pass the $arch variable through a
whole lot of function calls to ultimately also adapt the
hotplug code to take care of the new keyboard device.
Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
we change 'vga' to a property string and add a 'memory' property
with this, the user can better control the memory given to the virtual
gpu, this is especially useful for spice/qxl since high resolutions need
more memory
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
