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From: Anton Blanchard <>
Subject: [PATCH] powerpc: Linux cannot run with 0 cores
Date: Fri, 18 Jun 2010 10:33:06 +1000	[thread overview]
Message-ID: <20100618003306.GA3463@kryten> (raw)

If we configure with CONFIG_SMP=n or set NR_CPUS less than the number of
SMT threads we will set the max cores property to 0 in the
ibm,client-architecture-support structure. On new versions of firmware that
understand this property it obliges and terminates our partition.

Use DIV_ROUND_UP so we handle not only the CONFIG_SMP=n case but also the
case where NR_CPUS isn't a multiple of the number of SMT threads.

Signed-off-by: Anton Blanchard <>

Index: linux-2.6/arch/powerpc/kernel/prom_init.c
--- linux-2.6.orig/arch/powerpc/kernel/prom_init.c	2010-06-17 09:08:20.000000000 +1000
+++ linux-2.6/arch/powerpc/kernel/prom_init.c	2010-06-17 09:10:02.000000000 +1000
@@ -872,7 +872,7 @@ static void __init prom_send_capabilitie
 				    "ibm_architecture_vec structure inconsistent: 0x%x !\n",
 		} else {
-			*cores = NR_CPUS / prom_count_smt_threads();
+			*cores = DIV_ROUND_UP(NR_CPUS, prom_count_smt_threads());
 			prom_printf("Max number of cores passed to firmware: 0x%x\n",
 				    (unsigned long)*cores);

             reply	other threads:[~2010-06-18  0:33 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-06-18  0:33 Anton Blanchard [this message]
2010-06-18 18:02 ` [PATCH] powerpc: Linux cannot run with 0 cores Paul E. McKenney

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