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authorBenjamin Herrenschmidt <benh@kernel.crashing.org>2010-02-04 14:33:54 +1100
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2010-02-04 14:33:54 +1100
commitefec959f63de850fbd2442189f7dfc9c38efe251 (patch)
tree63824395c5ddb427cbcd115f975154b09ebb1334 /arch/powerpc/kernel/prom_init.c
parent28bb9ee13aa0ee4c57dc3568f539cc84920b43aa (diff)
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: Joel Schopp <jschopp@austin.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/kernel/prom_init.c')
-rw-r--r--arch/powerpc/kernel/prom_init.c64
1 files changed, 63 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
index 59d5bd1c064..5f306c4946e 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -710,7 +710,12 @@ static unsigned char ibm_architecture_vec[] = {
0,
0,
0,
- W(NR_CPUS), /* number of cores supported*/
+ /* 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 */
4 - 2, /* length */
@@ -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,