Re: [PATCH v2 0/8] Enable virtio-mem-ccw

On 2/4/25 10:06, David Hildenbrand wrote: > On 03.02.25 10:55, Michal Privoznik wrote: >> v2 of: >> >> https://lists.libvirt.org/archives/list/devel@lists.libvirt.org/ >> thread/KA2DGRIY7DAMNMYM4MBKLOJCB7YYEUKU/ >> > > I should probably play with this myself, but due to lack of a test > system where I can mess with systemd: > > Assuming we're on a s390x host (using KVM) and we specify: > > +    <memory model='virtio-mem'> > +      <target dynamicMemslots='yes'> > +        <size unit='KiB'>2097152</size> > +        <node>0</node> > +        <requested unit='KiB'>1048576</requested> > +      </target> > +    </memory> > > In particular, without > > +        <block unit='KiB'>2048</block> > > What would be the default value on a s390x host? > > In QEMU, we'd be using the default of 1 MiB on a s390x host, which > corresponds to the THP size. Note that on an x86_64 host, the default > will be 2 MiB. > > Ideally, we'd also be using the default of 1 MiB on an s390x host. > > How is the default value determined here? > > Thanks! > Current libvirt implementation does not generate a default. When not providing the element block an error occurs: error: block size must be a power of two When providing the element block the required minimum value is 1024KiB.