On 1/18/23 11:53, Thomas Huth wrote:
On 17/01/2023 14.31, Nina Schoetterl-Glausch wrote:
On Tue, 2023-01-17 at 08:30 +0100, Thomas Huth wrote:
On 16/01/2023 22.09, Nina Schoetterl-Glausch wrote:
On Thu, 2023-01-05 at 15:53 +0100, Pierre Morel wrote:
The modification of the CPU attributes are done through a monitor
commands.
It allows to move the core inside the topology tree to optimise
the cache usage in the case the host's hypervizor previously
moved the CPU.
The same command allows to modifiy the CPU attributes modifiers
like polarization entitlement and the dedicated attribute to notify
the guest if the host admin modified scheduling or dedication of a
vCPU.
With this knowledge the guest has the possibility to optimize the
usage of the vCPUs.
Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
...
+ s390_topology.sockets[s390_socket_nb(id)]--;
I suppose this function cannot run concurrently, so the same CPU
doesn't get removed twice.
QEMU has the so-called BQL - the Big Qemu Lock. Instructions handlers
are
normally called with the lock taken, see qemu_mutex_lock_iothread() in
target/s390x/kvm/kvm.c.
That is good to know, but is that the relevant lock here?
We don't want to concurrent qmp commands. I looked at the code and
it's pretty complicated.
Not sure, but I believe that QMP commands are executed from the main
iothread, so I think this should be safe? ... CC:-ing some more people
who might know the correct answer.
Thomas
That is what I understand from the doc too.
See:
docs/devel/qapi-code-gen.rst
One must specify allow-oob:true to avoid the BQL, default is false.
Regards,
Pierre
--
Pierre Morel
IBM Lab Boeblingen
