On Fri, Nov 05, 2021 at 03:52:13PM -0300, Daniel Henrique Barboza wrote: > > > On 11/5/21 10:51, Nicholas Piggin wrote: > > A configuration that specifies multiple nodes without distance info > > results in the non-local points in the FORM2 matrix having a distance of > > 0. This causes Linux to complain "Invalid distance value range" because > > a node distance is smaller than the local distance. > > > > Fix this by building a simple local / remote fallback for points where > > distance information is missing. > > Thanks for looking this up. I checked the output of this same scenario with > a FORM1 guest and 4 distance-less NUMA nodes. This is what I got: > > [root@localhost ~]# numactl -H > available: 4 nodes (0-3) > (...) > node distances: > node 0 1 2 3 > 0: 10 160 160 160 > 1: 160 10 160 160 > 2: 160 160 10 160 > 3: 160 160 160 10 > [root@localhost ~]# > > > With this patch we're getting '20' instead of '160' because you're using > NUMA_DISTANCE_DEFAULT, while FORM1 will default this case to the maximum > NUMA distance the kernel allows for that affinity (160). > > I do not have strong feelings about changing this behavior between FORM1 and > FORM2. I tested the same scenario with a x86_64 guest and they also uses '20' > in this case as well, so far as QEMU goes using NUMA_DISTANCE_DEFAULT is > consistent. > > Aneesh is already in CC, so I believe he'll let us know if there's something > we're missing and we need to preserve the '160' distance in FORM2 for this > case as well. > > For now: > > > > > > Signed-off-by: Nicholas Piggin <npig...@gmail.com> > > --- > > > Reviewed-by: Daniel Henrique Barboza <danielhb...@gmail.com>
Applied to ppc-for-6.2, thanks.
>
>
>
> > hw/ppc/spapr_numa.c | 22 +++++++++++++++++-----
> > 1 file changed, 17 insertions(+), 5 deletions(-)
> >
> > diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
> > index 5822938448..56ab2a5fb6 100644
> > --- a/hw/ppc/spapr_numa.c
> > +++ b/hw/ppc/spapr_numa.c
> > @@ -546,12 +546,24 @@ static void
> > spapr_numa_FORM2_write_rtas_tables(SpaprMachineState *spapr,
> > * NUMA nodes, but QEMU adds the default NUMA node without
> > * adding the numa_info to retrieve distance info from.
> > */
> > - if (src == dst) {
> > - distance_table[i++] = NUMA_DISTANCE_MIN;
> > - continue;
> > + distance_table[i] = numa_info[src].distance[dst];
> > + if (distance_table[i] == 0) {
> > + /*
> > + * In case QEMU adds a default NUMA single node when the
> > user
> > + * did not add any, or where the user did not supply
> > distances,
> > + * the value will be 0 here. Populate the table with a
> > fallback
> > + * simple local / remote distance.
> > + */
> > + if (src == dst) {
> > + distance_table[i] = NUMA_DISTANCE_MIN;
> > + } else {
> > + distance_table[i] = numa_info[src].distance[dst];
> > + if (distance_table[i] < NUMA_DISTANCE_MIN) {
> > + distance_table[i] = NUMA_DISTANCE_DEFAULT;
> > + }
> > + }
> > }
> > -
> > - distance_table[i++] = numa_info[src].distance[dst];
> > + i++;
> > }
> > }
> >
>
--
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_!
http://www.ozlabs.org/~dgibson
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