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Commit efec959f authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt
Browse files

powerpc/pseries: Pass more accurate number of supported cores to firmware 



Updated variant of a patch by Joel Schopp.

The field containing the number of supported cores which we pass to
firmware via the ibm,client-architecture call was set by a previous
patch statically as high as is possible (NR_CPUS).

However, that value isn't quite right for a system that supports
multiple threads per core, thus permitting the firmware to assign
more cores to a Linux partition than it can really cope with.

This patch improves it by using the device-tree to determine the
number of threads supported by the processors in order to adjust
the value passed to firmware.

Signed-off-by: default avatarJoel Schopp <jschopp@austin.ibm.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 28bb9ee1

arch/powerpc/kernel/prom_init.c

+63 −1
Original line number Diff line number Diff line
@@ -710,6 +710,11 @@ static unsigned char ibm_architecture_vec[] = { 
	0,

	0,

	0,

	/* WARNING: The offset of the "number of cores" field below

	 * must match by the macro below. Update the definition if

	 * the structure layout changes.

	 */

#define IBM_ARCH_VEC_NRCORES_OFFSET	100

	W(NR_CPUS),			/* number of cores supported */



	/* option vector 6: IBM PAPR hints */
@@ -807,13 +812,70 @@ static struct fake_elf { 
	}

};



static int __init prom_count_smt_threads(void)

{

	phandle node;

	char type[64];

	unsigned int plen;



	/* Pick up th first CPU node we can find */

	for (node = 0; prom_next_node(&node); ) {

		type[0] = 0;

		prom_getprop(node, "device_type", type, sizeof(type));



		if (strcmp(type, RELOC("cpu")))

			continue;

		/*

		 * There is an entry for each smt thread, each entry being

		 * 4 bytes long.  All cpus should have the same number of

		 * smt threads, so return after finding the first.

		 */

		plen = prom_getproplen(node, "ibm,ppc-interrupt-server#s");

		if (plen == PROM_ERROR)

			break;

		plen >>= 2;

		prom_debug("Found 0x%x smt threads per core\n", (unsigned long)plen);



		/* Sanity check */

		if (plen < 1 || plen > 64) {

			prom_printf("Threads per core 0x%x out of bounds, assuming 1\n",

				    (unsigned long)plen);

			return 1;

		}

		return plen;

	}

	prom_debug("No threads found, assuming 1 per core\n");



	return 1;



}





static void __init prom_send_capabilities(void)

{

	ihandle elfloader, root;

	prom_arg_t ret;

	u32 *cores;



	root = call_prom("open", 1, 1, ADDR("/"));

	if (root != 0) {

		/* We need to tell the FW about the number of cores we support.

		 *

		 * To do that, we count the number of threads on the first core

		 * (we assume this is the same for all cores) and use it to

		 * divide NR_CPUS.

		 */

		cores = (u32 *)PTRRELOC(&ibm_architecture_vec[IBM_ARCH_VEC_NRCORES_OFFSET]);

		if (*cores != NR_CPUS) {

			prom_printf("WARNING ! "

				    "ibm_architecture_vec structure inconsistent: 0x%x !\n",

				    *cores);

		} else {

			*cores = NR_CPUS / prom_count_smt_threads();

			prom_printf("Max number of cores passed to firmware: 0x%x\n",

				    (unsigned long)*cores);

		}



		/* try calling the ibm,client-architecture-support method */

		prom_printf("Calling ibm,client-architecture-support...");

		if (call_prom_ret("call-method", 3, 2, &ret,