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Re: [Qemu-devel] [Qemu-ppc] [PATCH] spapr: Correct compatibility mode se

From: Daniel Henrique Barboza
Subject: Re: [Qemu-devel] [Qemu-ppc] [PATCH] spapr: Correct compatibility mode setting for hotplugged CPUs
Date: Thu, 4 Jan 2018 16:02:05 -0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0

On 01/04/2018 02:24 AM, David Gibson wrote:
Currently the pseries machine sets the compatibility mode for the
guest's cpus in two places: 1) at machine reset and 2) after CAS

This means that if we set or negotiate a compatiblity mode, then


hotplug a cpu, the hotplugged cpu doesn't get the right mode set and
will incorrectly have the full native features.

To correct this, we set the compatibility mode on a cpu when it is
brought online with the 'start-cpu' RTAS call.  Given that we no
longer need to set the compatibility mode on all CPUs at machine
reset, so we change that to only set the mode for the boot cpu.

Signed-off-by: David Gibson <address@hidden>
Reviewed-by: Daniel Henrique Barboza <address@hidden>
  hw/ppc/spapr.c      | 2 +-
  hw/ppc/spapr_rtas.c | 8 ++++++++
  2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index e22888ba06..d1acfe8858 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1510,7 +1510,7 @@ static void spapr_machine_reset(void)
          spapr->ov5_cas = spapr_ovec_new();

-        ppc_set_compat_all(spapr->max_compat_pvr, &error_fatal);
+        ppc_set_compat(first_ppc_cpu, spapr->max_compat_pvr, &error_fatal);

      fdt = spapr_build_fdt(spapr, rtas_addr, spapr->rtas_size);
diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
index 4bb939d3d1..2ed00548c1 100644
--- a/hw/ppc/spapr_rtas.c
+++ b/hw/ppc/spapr_rtas.c
@@ -163,6 +163,7 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, 
sPAPRMachineState *spapr,
          CPUState *cs = CPU(cpu);
          CPUPPCState *env = &cpu->env;
          PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
+        Error *local_err = NULL;

          if (!cs->halted) {
              rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
@@ -174,6 +175,13 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, 
sPAPRMachineState *spapr,
           * new cpu enters */

+        /* Set compatibility mode to match existing cpus */
+        ppc_set_compat(cpu, POWERPC_CPU(first_cpu)->compat_pvr, &local_err);
+        if (local_err) {
+            rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
+            return;
+        }
          env->msr = (1ULL << MSR_SF) | (1ULL << MSR_ME);

          /* Enable Power-saving mode Exit Cause exceptions for the new CPU */

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