On Wed, 2010-01-27 at 17:29 +1030, Michael Neuling wrote:

quoted

On 64-bit kernels we currently have a 512 byte struct paca_struct for
each cpu (usually just called "the paca"). Currently they are statically
allocated, which means a kernel built for a large number of cpus will
waste a lot of space if it's booted on a machine with few cpus.

We can avoid that by only allocating the number of pacas we need at
boot. However this is complicated by the fact that we need to access
the paca before we know how many cpus there are in the system.

The solution is to dynamically allocate enough space for NR_CPUS pacas,
but then later in boot when we know how many cpus we have, we free any
unused pacas.

Lightly booted on Legacy iSeries & pSeries LPAR.

Signed-off-by: Michael Ellerman <redacted>

<snip>

quoted

--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c

@@ -493,6 +493,8 @@ void __init smp_setup_cpu_maps(void)
 	 * here will have to be reworked
 	 */
 	cpu_init_thread_core_maps(nthreads);
+
+	free_unused_pacas();

This is still barfing for me on 32bit.

Darn, what config? I built at least one :)

Putting an #include <asm/paca.h> at the top of setup-common.c fixes it.

Gah, I saw it was coming via somewhere else but decided not to add it,
wrong decision :)

cheers