On Fri, Dec 04, 2020 at 13:17:52 +0100, Peter Krempa wrote: > On Thu, Dec 03, 2020 at 13:36:23 +0100, Michal Privoznik wrote: > > QEMU gained this new virtio-mem model. It's similar to pc-dimm > > in a sense that guest uses it as memory, but in a sense very > > different from it as it can dynamically change allocation, > > without need for hotplug. More specifically, the device has two > > attributes more (it has more of course, but these two are > > important here): > > > > 1) block-size - the granularity of the device. You can imagine > > the device being divided into blocks, each 'block-size' long. > > > > 2) requested-size - the portion of the device that is in use by > > the guest. > > > > And it all works like this: at guest startup/hotplug both > > block-size and requested-size are specified. When sysadmin wants > > to give some more memory to the guest, or take some back, they > > change the 'requested-size' attribute which is propagated to the > > guest where virtio-mem module takes corresponding action. > > This means, that 'requested-size' must be a whole number product > > of 'block-size' and of course has to be in rage [0, max-size] > > (including). The 'max-size' is yet another attribute but if not > > set it's "inherited" from corresponding memory-backend-* object. > > > > Therefore, two new elements are introduced under <target/>, to > > reflect these attributes: > > > > <memory model='virtio'> > > <target> > > <size unit='KiB'>4194304</size> > > <node>0</node> > > <block unit='KiB'>2048</block> > > <requested unit='KiB'>524288</requested> > > </target> > > <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/> > > </memory> > > > > The intent here is that <requested/> will be allowed to change > > via virDomainUpdateDeviceFlags() API. > > > > Note, QEMU does inform us about success of allocation via an > > event - this is covered in next patches. > > > > Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx> > > --- > > docs/formatdomain.rst | 22 ++++ > > docs/schemas/domaincommon.rng | 10 ++ > > src/conf/domain_conf.c | 103 ++++++++++++++++-- > > src/conf/domain_conf.h | 5 + > > .../memory-hotplug-virtio-mem.xml | 78 +++++++++++++ > > ...emory-hotplug-virtio-mem.x86_64-latest.xml | 1 + > > tests/qemuxml2xmltest.c | 1 + > > 7 files changed, 213 insertions(+), 7 deletions(-) > > create mode 100644 tests/qemuxml2argvdata/memory-hotplug-virtio-mem.xml > > create mode 120000 tests/qemuxml2xmloutdata/memory-hotplug-virtio-mem.x86_64-latest.xml Disregard any comments about size being actual size ...
