Quoting Daniel P. Berrange (berra...@redhat.com):
> If a previous commit I fixed the incorrect handling of vcpu pids
> for TCG mode QEMU:
>
> commit b07f3d821dfb11a118ee75ea275fd6ab737d9500
> Author: Daniel P. Berrange <berra...@redhat.com>
> Date: Thu Dec 18 16:34:39 2014 +0000
>
> Don't setup fake CPU pids for old QEMU
>
> The code assumes that def->vcpus == nvcpupids, so when we setup
> fake CPU pids for old QEMU with nvcpupids == 1, we cause the
> later code to read off the end of the array. This has fun results
> like sche_setaffinity(0, ...) which changes libvirtd's own CPU
> affinity, or even better sched_setaffinity($RANDOM, ...) which
> changes the affinity of a random OS process.
>
> The intent was that this would merely disable the ability to set
> per-vCPU affinity. It should still have been possible to set VM
> level host CPU affinity.
>
> Unfortunately, when you set <vcpu cpuset='0-1'>4</vcpu>, the XML
> parser will internally take this & initialize an entry in the
> def->cputune.vcpupin array for every VCPU. IOW this is implicitly
> being treated as
>
> <cputune>
> <vcpupin cpuset='0-1' vcpu='0'/>
> <vcpupin cpuset='0-1' vcpu='1'/>
> <vcpupin cpuset='0-1' vcpu='2'/>
> <vcpupin cpuset='0-1' vcpu='3'/>
> </cputune>
>
> Even more fun, the faked cputune elements are hidden from view when
> querying the live XML, because their cpuset mask is the same as the
> VM default cpumask.
>
> The upshot was that it was impossible to set VM level CPU affinity.
>
> To fix this we must update qemuProcessSetVcpuAffinities so that it
> only reports a fatal error if the per-VCPU cpu mask is different
> from the VM level cpu mask.
>
> Signed-off-by: Daniel P. Berrange <berra...@redhat.com>
Thanks, confirmed this let's me place qemu in a cpuset. (Noting that
'virsh edit' always ends up squashing the cputune section when the
cpusets are identical, but that should all be reasonable)
Acked-by: Serge E. Hallyn <serge.hal...@ubuntu.com>
Tested-by: Serge E. Hallyn <serge.hal...@ubuntu.com>
> ---
> src/qemu/qemu_process.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
> index d5df60d..e8c532f 100644
> --- a/src/qemu/qemu_process.c
> +++ b/src/qemu/qemu_process.c
> @@ -2497,9 +2497,18 @@ qemuProcessSetVcpuAffinities(virDomainObjPtr vm)
> return 0;
>
> if (priv->vcpupids == NULL) {
> - virReportError(VIR_ERR_OPERATION_INVALID,
> - "%s", _("cpu affinity is not supported"));
> - return -1;
> + /* If any CPU has custom affinity that differs from the
> + * VM default affinity, we must reject it
> + */
> + for (n = 0; n < def->vcpus; n++) {
> + if (!virBitmapEqual(def->cpumask,
> + def->cputune.vcpupin[n]->cpumask)) {
> + virReportError(VIR_ERR_OPERATION_INVALID,
> + "%s", _("cpu affinity is not supported"));
> + return -1;
> + }
> + }
> + return 0;
> }
>
> for (n = 0; n < def->vcpus; n++) {
> --
> 2.1.0
>
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