From efec959f63de850fbd2442189f7dfc9c38efe251 Mon Sep 17 00:00:00 2001 From: Benjamin Herrenschmidt Date: Thu, 4 Feb 2010 14:33:54 +1100 Subject: [PATCH] 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 Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/prom_init.c | 64 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 63 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c index 59d5bd1..5f306c4 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, -- 2.7.4