Re: [PATCH v2 20/27] conf: Introduce virtio-mem <memory/> model

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(a)redhat.com&gt; > --- > 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