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Re: [Qemu-devel] [PATCH v4 05/16] pc: enforce adding CPUs contiguously a
From: |
Igor Mammedov |
Subject: |
Re: [Qemu-devel] [PATCH v4 05/16] pc: enforce adding CPUs contiguously and removing them in opposit order |
Date: |
Fri, 15 Jul 2016 11:33:16 +0200 |
On Thu, 14 Jul 2016 14:10:24 -0400
Bandan Das <address@hidden> wrote:
> Igor Mammedov <address@hidden> writes:
>
> > it will still allow us to use cpu_index as migration instance_id
> > since when CPUs are added contiguously (from the first to the last)
> > and removed in opposite order, cpu_index stays stable and it's
> > reproducable on destination side.
> >
> > Signed-off-by: Igor Mammedov <address@hidden>
> > ---
> > While there is work in progress to support migration when there are holes
> > in cpu_index range resulting from out-of-order plug or unplug, this patch
> > is intended as a last resort if no easy, risk-free and elegant solution
> > emerges before 2.7 dev cycle ends.
>
> I think this (or a modified version) is appropriate comment
> material to accompany the changes. Ok if you are sure this code
> is short-lived, but if it stays longer, a comment is definitely
> helpful. Maybe a bit of reasoning added to the error message is
> fine too.
dwg is looking at cpu_index refactoring but that's not 2.7 material,
this patch is doing what the similar spapr patch did
(which David applied to his ppc queue).
Perhaps moving comment under --- to commit message itself would
be better as to leave trace of future refactoring plans.
> > ---
> > hw/i386/pc.c | 34 ++++++++++++++++++++++++++++++++++
> > 1 file changed, 34 insertions(+)
> >
> > diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> > index 33c5f97..75a92d0 100644
> > --- a/hw/i386/pc.c
> > +++ b/hw/i386/pc.c
> > @@ -1762,6 +1762,23 @@ static void pc_cpu_unplug_request_cb(HotplugHandler
> > *hotplug_dev,
> > goto out;
> > }
> >
> > + if (idx < pcms->possible_cpus->len - 1 &&
> > + pcms->possible_cpus->cpus[idx + 1].cpu != NULL) {
> > + X86CPU *cpu;
> > +
> > + for (idx = pcms->possible_cpus->len - 1;
> > + pcms->possible_cpus->cpus[idx].cpu == NULL; idx--) {
> > + ;;
> > + }
> > +
> > + cpu = X86_CPU(pcms->possible_cpus->cpus[idx].cpu);
> > + error_setg(&local_err, "CPU [socket-id: %u, core-id: %u,"
> > + " thread-id: %u] should be removed first",
> > + cpu->socket_id, cpu->core_id, cpu->thread_id);
> > + goto out;
> > +
> > + }
> > +
> > hhc = HOTPLUG_HANDLER_GET_CLASS(pcms->acpi_dev);
> > hhc->unplug_request(HOTPLUG_HANDLER(pcms->acpi_dev), dev, &local_err);
> >
> > @@ -1860,6 +1877,23 @@ static void pc_cpu_pre_plug(HotplugHandler
> > *hotplug_dev,
> > return;
> > }
> >
> > + if (idx != 0 && pcms->possible_cpus->cpus[idx - 1].cpu == NULL) {
> > + PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(pcms);
> > +
> > + for (idx = 1; pcms->possible_cpus->cpus[idx].cpu != NULL; idx++) {
> > + ;;
> > + }
> > +
> > + x86_topo_ids_from_apicid(pcms->possible_cpus->cpus[idx].arch_id,
> > + smp_cores, smp_threads, &topo);
> > +
> > + if (!pcmc->legacy_cpu_hotplug) {
> > + error_setg(errp, "CPU [socket: %u, core: %u, thread: %u]
> > should be"
> > + " added first", topo.pkg_id, topo.core_id,
> > topo.smt_id);
> > + return;
> > + }
> > + }
> > +
> > /* if 'address' properties socket-id/core-id/thread-id are not set,
> > set them
> > * so that query_hotpluggable_cpus would show correct values
> > */
[Qemu-devel] [PATCH v4 05/16] pc: enforce adding CPUs contiguously and removing them in opposit order, Igor Mammedov, 2016/07/14
[Qemu-devel] [PATCH v5 05/16] pc: enforce adding CPUs contiguously and removing them in opposit order, Igor Mammedov, 2016/07/18
Re: [Qemu-devel] [PATCH v4 05/16] pc: enforce adding CPUs contiguously and removing them in opposit order, Eric Blake, 2016/07/18
[Qemu-devel] [PATCH v4 06/16] pc: cpu: allow device_add to be used with x86 cpu, Igor Mammedov, 2016/07/14
[Qemu-devel] [PATCH v4 07/16] pc: implement query-hotpluggable-cpus callback, Igor Mammedov, 2016/07/14
[Qemu-devel] [PATCH v4 09/16] apic: drop APICCommonState.idx and use APIC ID as index in local_apics[], Igor Mammedov, 2016/07/14