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[PATCH 1/1] spapr.c: remove 'ibm,chip-id' from DT

From: Daniel Henrique Barboza
Subject: [PATCH 1/1] spapr.c: remove 'ibm,chip-id' from DT
Date: Thu, 11 Mar 2021 12:15:57 -0300

The attribute 'ibm,chip-id' does not exist in PAPR. This alone would be
enough reason to remove it from the spapr DT, but before doing that,
let's give a brief context on how and why it was introduced.

'ibm,chip-id' was added in the spapr DT by commit 10582ff83279. This
commit references kernel commit 256f2d4b463d ("powerpc: Use ibm, chip-id
property to compute cpu_core_mask if available"). In this kernel commit,
the 'ibm,chip-id' DT attribute is being used to calculate the
cpu_core_mask in traverse_siblings_chip_id(). This function still need
to consider 'ibm,chip-id' not being available as well to avoid breaking
older guests.

Later on, kernel commit df52f6714071 ("powerpc/smp: Rework CPU topology
construction") removed traverse_siblings_chip_id() and its callers,
making the CPU topology calculation independent of the 'ibm,chip-id'
attribute. Today, the kernel uses 'ibm,chip-id' for PowerNV related code
only - the pseries kernel does not rely on it.

All that said, since it's not in PAPR and the pseries kernel does not
rely on it, let's remove ibm,chip-id from the DT.

CC: Alexey Kardashevskiy <aik@ozlabs.ru>
Suggested-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
 hw/ppc/spapr.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 85fe65f894..d2e448fd9c 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -657,7 +657,6 @@ static void spapr_dt_cpu(CPUState *cs, void *fdt, int 
     uint32_t page_sizes_prop[64];
     size_t page_sizes_prop_size;
     unsigned int smp_threads = ms->smp.threads;
-    uint32_t vcpus_per_socket = smp_threads * ms->smp.cores;
     uint32_t pft_size_prop[] = {0, cpu_to_be32(spapr->htab_shift)};
     int compat_smt = MIN(smp_threads, ppc_compat_max_vthreads(cpu));
     SpaprDrc *drc;
@@ -744,9 +743,6 @@ static void spapr_dt_cpu(CPUState *cs, void *fdt, int 
     spapr_dt_pa_features(spapr, cpu, fdt, offset);
-    _FDT((fdt_setprop_cell(fdt, offset, "ibm,chip-id",
-                           cs->cpu_index / vcpus_per_socket)));
     _FDT((fdt_setprop(fdt, offset, "ibm,pft-size",
                       pft_size_prop, sizeof(pft_size_prop))));

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