Memory slots are required only for DIMM-like devices, but the maximum
memory address space is relevant also for other non-DIMM memory devices
such as virtio-mem. Allow configurations where no slots are added.
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Memory slots are required only for DIMM-like devices, while other
devices defined via <memory> such as virtio-mem may use the PCI bus and
thus do not require/consume a memory slot.
Fix the validation code to calculate the required count of memory
devices only for DIMMs and NVDIMMs.
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Both virtio-mem and virtio-pmem devices have '.memaddr' attribute
which controls the address where they are mapped in the guest
memory. Ideally, users do not need to specify this as QEMU does
the right thing and computes addresses automatically on startup.
But soon, we will need to record this address as it is part of
guest ABI. And also, there might be some users that want to
control this value. Now, we are in a bit of a pickle, because
both these device types already have a PCI address, therefore we
can't just use <address/> blindly. But what we can do, is
introduce <address/> under the <target/> element. This is also
more conceptual, as knobs under <target/> control guest visible
config of memory device (and .memaddr surely falls into that
category).
NB, SgxEPCDeviceInfo struct in QMP definition also has .memaddr
attribute, but because of the way we build cmd line there's no
(easy) way to set the attribute. So ignore that for now.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
This is a perfectly valid configuration that we need to keep
working, so add test coverage for it.
Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Upcoming patches will modify how we populate the capability cache in
tests to be more saner. This also means that the emulator binary and
architecture used in the test files using real capabilities must match
what the real capabilities have.
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
The virtio-mem is paravirtualized mechanism of adding/removing
memory to/from a VM. A virtio-mem-pci device is split into blocks
of equal size which are then exposed (all or only a requested
portion of them) to the guest kernel to use as regular memory.
Therefore, the device has two important attributes:
1) block-size, which defines the size of a block
2) requested-size, which defines how much memory (in bytes)
is the device requested to expose to the guest.
The 'block-size' is configured on command line and immutable
throughout device's lifetime. The 'requested-size' can be set on
the command line too, but also is adjustable via monitor. In
fact, that is how management software places its requests to
change the memory allocation. If it wants to give more memory to
the guest it changes 'requested-size' to a bigger value, and if it
wants to shrink guest memory it changes the 'requested-size' to a
smaller value. Note, value of zero means that guest should
release all memory offered by the device. Of course, guest has to
cooperate. Therefore, there is a third attribute 'size' which is
read only and reflects how much memory the guest still has. This
can be different to 'requested-size', obviously. Because of name
clash, I've named it 'current' and it is dealt with in future
commits (it is a runtime information anyway).
In the backend, memory for virtio-mem is backed by usual objects:
memory-backend-{ram,file,memfd} and their size puts the cap on
the amount of memory that a virtio-mem device can offer to a
guest. But we are already able to express this info using <size/>
under <target/>.
Therefore, we need only two more elements to cover 'block-size'
and 'requested-size' attributes. This is the XML I've came up
with:
<memory model='virtio-mem'>
<source>
<nodemask>1-3</nodemask>
<pagesize unit='KiB'>2048</pagesize>
</source>
<target>
<size unit='KiB'>2097152</size>
<node>0</node>
<block unit='KiB'>2048</block>
<requested unit='KiB'>1048576</requested>
</target>
<address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
</memory>
I hope by now it is obvious that:
1) 'requested-size' must be an integer multiple of
'block-size', and
2) virtio-mem-pci device goes onto PCI bus and thus needs PCI
address.
Then there is a limitation that the minimal 'block-size' is
transparent huge page size (I'll leave this without explanation).
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
