Re: [Qemu-devel] [PATCH for 2.13 v3 1/2] spapr: Add ibm, max-associativity-domains property

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

On Mon, Apr 16, 2018 at 07:47:29PM +0300, Serhii Popovych wrote:
> Bharata B Rao wrote:
> > On Wed, Apr 11, 2018 at 02:41:59PM -0400, Serhii Popovych wrote:
> >> Now recent kernels (i.e. since linux-stable commit a346137e9142
> >> ("powerpc/numa: Use ibm,max-associativity-domains to discover possible nodes")
> >> support this property to mark initially memory-less NUMA nodes as "possible"
> >> to allow further memory hot-add to them.
> >>
> >> Advertise this property for pSeries machines to let guest kernels detect
> >> maximum supported node configuration and benefit from kernel side change
> >> when hot-add memory to specific, possibly empty before, NUMA node.
> >>
> >> Signed-off-by: Serhii Popovych <spopovyc@redhat.com>
> >> ---
> >>  hw/ppc/spapr.c | 10 ++++++++++
> >>  1 file changed, 10 insertions(+)
> >>
> >> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> >> index a81570e..c05bbad 100644
> >> --- a/hw/ppc/spapr.c
> >> +++ b/hw/ppc/spapr.c
> >> @@ -910,6 +910,13 @@ static void spapr_dt_rtas(sPAPRMachineState *spapr, void *fdt)
> >>          0, cpu_to_be32(SPAPR_MEMORY_BLOCK_SIZE),
> >>          cpu_to_be32(max_cpus / smp_threads),
> >>      };
> >> +    uint32_t maxdomains[] = {
> >> +        cpu_to_be32(4),
> >> +        cpu_to_be32(0),
> >> +        cpu_to_be32(0),
> >> +        cpu_to_be32(0),
> >> +        cpu_to_be32(nb_numa_nodes - 1),
> >> +    };
> >>
> >>      _FDT(rtas = fdt_add_subnode(fdt, 0, "rtas"));
> >>
> >> @@ -946,6 +953,9 @@ static void spapr_dt_rtas(sPAPRMachineState *spapr, void *fdt)
> >>      _FDT(fdt_setprop(fdt, rtas, "ibm,associativity-reference-points",
> >>                       refpoints, sizeof(refpoints)));
> >>
> >> +    _FDT(fdt_setprop(fdt, rtas, "ibm,max-associativity-domains",
> >> +                     maxdomains, sizeof(maxdomains)));
> >> +
> >>      _FDT(fdt_setprop_cell(fdt, rtas, "rtas-error-log-max",
> >>                            RTAS_ERROR_LOG_MAX));
> >>      _FDT(fdt_setprop_cell(fdt, rtas, "rtas-event-scan-rate",
> >> -- 
> >> 1.8.3.1
> > 
> > This commit causes hash guest with latest guest kernel to hang at early boot.
> 
> I use v4.16 tag from stable and can't reproduce on P8 machine reported
> issue.
> 
> Could you please share more details about your setup, kernel commit id
> you spot problem?

I am on 4.16.0-rc7 (commit id: 0b412605ef5f)

BTW this happens only for non-NUMA guest.

Regards,
Bharata.