On Wed, Jul 06, 2016 at 01:55:25PM +0530, Bharata B Rao wrote: > On Wed, Jul 06, 2016 at 07:25:44AM +0200, Igor Mammedov wrote: > > On Tue, 5 Jul 2016 18:13:22 +0530 > > Bharata B Rao <bhar...@linux.vnet.ibm.com> wrote: > > > > > On Tue, Jul 05, 2016 at 09:15:51AM +0200, Igor Mammedov wrote: > > > > On Tue, 5 Jul 2016 10:12:49 +0530 > > > > Bharata B Rao <bhar...@linux.vnet.ibm.com> wrote: > > > > > > > > > Introduce CPUState.prefer_arch_id_over_cpu_index and > > > > > MachineClass.prefer_arch_id_over_cpu_index that allow target > > > > > machines to optionally switch to using arch_id instead of > > > > > cpu_index as instance_id in vmstate_register(). This will help > > > > > allow successful migration in cases where holes are introduced in > > > > > cpu_index range after CPU hot removals. > > > > > > > > > > Whether to use arch_id or cpu_index is based on machine type > > > > > version and hence added > > > > > MachineClass.prefer_arch_id_over_cpu_index. However the > > > > > enforcement is via and during CPU creation and hence added > > > > > CPUState.prefer_arch_id_over_cpu_index. So it becomes a two step > > > > > process for the target to enable the use of arch_id: > > > > > > > > > > 1. Set MachineClass.prefer_arch_id_over_cpu_index. > > > > > 2. Ensure CPUState.prefer_arch_id_over_cpu_index is set for all > > > > > CPUs based on 1. above. > > > > > > > > > > Suggested-by: Igor Mammedov <imamm...@redhat.com> > > > > > Signed-off-by: Bharata B Rao <bhar...@linux.vnet.ibm.com> > > > > > --- > > > > > exec.c | 10 ++++++++-- > > > > > include/hw/boards.h | 1 + > > > > > include/qom/cpu.h | 4 ++++ > > > > > 3 files changed, 13 insertions(+), 2 deletions(-) > > > > > > > > > > diff --git a/exec.c b/exec.c > > > > > index 8ce8e90..7cc1d06 100644 > > > > > --- a/exec.c > > > > > +++ b/exec.c > > > > > @@ -616,15 +616,21 @@ static void cpu_release_index(CPUState *cpu) > > > > > bitmap_clear(cpu_index_map, cpu->cpu_index, 1); > > > > > } > > > > > > > > > > +/* > > > > > + * TODO: cpu_index and instance_id are of type int > > > > > while .get_arch_id()is > > > > > + * of type int64_t. What is the consequence of changing > > > > > instance_id to int64_t ? > > > > > + */ > > > > ARM potentially could have get_arch_id() == MPIDR (return 64bit int) > > > > that would get truncated in this case. > > > > > > > > I wonder if we could add "int CPUState::migration_id" and let > > > > machine code set it to what it uses for stable cpu id and then > > > > cpu_realize could call vmstate_register with it. > > > > > > Hmm how would that help ? instance_id argument to vmstate_register() > > > is being treated as 32 bit integer as pointed by Greg earlier. > > > > > > If we want to use 64 bit arch_id/migration_id as instance_id arg in > > > vmstate_register, shouldn't we be changing instance_id to 64 bit ? > > Trying to extend instance_id from 32bit to 64bit, looks hard to me as > > it's on wire format so it's not possible to change without breaking > > compatibility. > > > > That's why dedicated migration_id should also be 32bit integer to keep > > it compatible with vmstate_foo() magic. On x86 and ARM that id will be > > in range [0..maxcpus), it's stable index in possible_cpus array. > > Since we were planning to use arch_id (aka device tree id) as the stable > index for CPU cores on PowerPC, we would have to use int64_t arch_id > itself as int instance_id I suppose. The range could be > [0...maxcpus*8] for us.
Huh? I don't see how this comment relates to the one before.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
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