Re: [Qemu-devel] [PATCH 13/13] target-ppc: Give a meaningful error if too many threads are specified

[David Gibson <dwg@au1.ibm.com>]

On Tue, Dec 04, 2012 at 01:42:17PM +1100, David Gibson wrote:
> From: Mike Qiu <qiudayu@linux.vnet.ibm.com>

Oops, messed this one up, build error for user only builds.  Fixed
version below.

>From d2cc6bcee4737647c4bbbf65d3c0129d4a119dd3 Mon Sep 17 00:00:00 2001
From: Mike Qiu <qiudayu@linux.vnet.ibm.com>
Date: Tue, 4 Dec 2012 10:52:14 +1100
Subject: [PATCH] target-ppc: Give a meaningful error if too many threads are
 specified

Currently the target-ppc tcg code only supports a single thread.  You can
specify more, but they're treated identically to multiple cores.  On KVM
we obviously can't support more threads than the hardware; if more are
specified it will cause strange and cryptic errors.

This patch clarifies the situation by giving a simple meaningful error if
more threads are specified than we can support.

Signed-off-by: Mike Qiu <qiudayu@linux.vnet.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 target-ppc/translate_init.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
index dba572f..bb054a7 100644
--- a/target-ppc/translate_init.c
+++ b/target-ppc/translate_init.c
@@ -28,6 +28,7 @@
 #include <kvm.h>
 #include "kvm_ppc.h"
 #include "arch_init.h"
+#include "cpus.h"
 
 //#define PPC_DUMP_CPU
 //#define PPC_DEBUG_SPR
@@ -10037,6 +10038,10 @@ static int ppc_fixup_cpu(CPUPPCState *env)
 
 int cpu_ppc_register_internal (CPUPPCState *env, const ppc_def_t *def)
 {
+#if !defined(CONFIG_USER_ONLY)
+    int max_smt = kvmppc_smt_threads();
+#endif
+
     env->msr_mask = def->msr_mask;
     env->mmu_model = def->mmu_model;
     env->excp_model = def->excp_model;
@@ -10046,6 +10051,13 @@ int cpu_ppc_register_internal (CPUPPCState *env, const ppc_def_t *def)
     env->flags = def->flags;
     env->bfd_mach = def->bfd_mach;
     env->check_pow = def->check_pow;
+#if !defined(CONFIG_USER_ONLY)
+    if (smp_threads > max_smt) {
+        fprintf(stderr, "Cannot support more than %d threads on PPC with %s\n",
+                max_smt, kvm_enabled() ? "KVM" : "TCG");
+        exit(1);
+    }
+#endif
 
 #if defined(TARGET_PPC64)
     if (def->sps)

-- 
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