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To: qemu-devel@nongnu.org
Cc: qemu-stable@nongnu.org, Harsh Prateek Bora <harshpb@linux.ibm.com>,
 Anushree Mathur <anushree.mathur@linux.vnet.ibm.com>,
 Nicholas Piggin <npiggin@gmail.com>, Michael Tokarev <mjt@tls.msk.ru>
Subject: [Stable-9.1.3 11/58] ppc/spapr: fix drc index mismatch for partially
 enabled vcpus
Date: Mon, 27 Jan 2025 23:24:57 +0300
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From: Michael Tokarev <mjt@tls.msk.ru>
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In case when vcpus are explicitly enabled/disabled in a non-consecutive
order within a libvirt xml, it results in a drc index mismatch during
vcpu hotplug later because the existing logic uses vcpu id to derive the
corresponding drc index which is not correct. Use env->core_index to
derive a vcpu's drc index as appropriate to fix this issue.

For ex, for the given libvirt xml config:
  <vcpus>
    <vcpu id=3D'0' enabled=3D'yes' hotpluggable=3D'no'/>
    <vcpu id=3D'1' enabled=3D'yes' hotpluggable=3D'yes'/>
    <vcpu id=3D'2' enabled=3D'no' hotpluggable=3D'yes'/>
    <vcpu id=3D'3' enabled=3D'yes' hotpluggable=3D'yes'/>
    <vcpu id=3D'4' enabled=3D'no' hotpluggable=3D'yes'/>
    <vcpu id=3D'5' enabled=3D'yes' hotpluggable=3D'yes'/>
    <vcpu id=3D'6' enabled=3D'no' hotpluggable=3D'yes'/>
    <vcpu id=3D'7' enabled=3D'no' hotpluggable=3D'yes'/>
  </vcpus>

We see below error on guest console with "virsh setvcpus <domain> 5" :

pseries-hotplug-cpu: CPU with drc index 10000002 already exists

This patch fixes the issue by using correct drc index for explicitly
enabled vcpus during init.

Reported-by: Anushree Mathur <anushree.mathur@linux.vnet.ibm.com>
Tested-by: Anushree Mathur <anushree.mathur@linux.vnet.ibm.com>
Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
(cherry picked from commit e8185fdc63e1db1efba695aae568fae8a075a815)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 370d7c35d3..0307953fe5 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -758,7 +758,7 @@ static void spapr_dt_cpu(CPUState *cs, void *fdt, int o=
ffset,
     uint32_t radix_AP_encodings[PPC_PAGE_SIZES_MAX_SZ];
     int i;
=20
-    drc =3D spapr_drc_by_id(TYPE_SPAPR_DRC_CPU, index);
+    drc =3D spapr_drc_by_id(TYPE_SPAPR_DRC_CPU, env->core_index);
     if (drc) {
         drc_index =3D spapr_drc_index(drc);
         _FDT((fdt_setprop_cell(fdt, offset, "ibm,my-drc-index", drc_index)=
));
--=20
2.39.5