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2011-05-05net: Add sendmmsg socket system callAnton Blanchard2-1/+3
This patch adds a multiple message send syscall and is the send version of the existing recvmmsg syscall. This is heavily based on the patch by Arnaldo that added recvmmsg. I wrote a microbenchmark to test the performance gains of using this new syscall: http://ozlabs.org/~anton/junkcode/sendmmsg_test.c The test was run on a ppc64 box with a 10 Gbit network card. The benchmark can send both UDP and RAW ethernet packets. 64B UDP batch pkts/sec 1 804570 2 872800 (+ 8 %) 4 916556 (+14 %) 8 939712 (+17 %) 16 952688 (+18 %) 32 956448 (+19 %) 64 964800 (+20 %) 64B raw socket batch pkts/sec 1 1201449 2 1350028 (+12 %) 4 1461416 (+22 %) 8 1513080 (+26 %) 16 1541216 (+28 %) 32 1553440 (+29 %) 64 1557888 (+30 %) We see a 20% improvement in throughput on UDP send and 30% on raw socket send. [ Add sparc syscall entries. -DaveM ] Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2011-05-04powerpc/pseries: Add page coalescing supportBrian King3-1/+19
Adds support for page coalescing, which is a feature on IBM Power servers which allows for coalescing identical pages between logical partitions. Hint text pages as coalesce candidates, since they are the most likely pages to be able to be coalesced between partitions. This patch also exports some page coalescing statistics available from firmware via lparcfg. [BenH: Moved a couple of things around to fix compile problems] Signed-off-by: Brian King <brking@linux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-05-04powerpc: Convert old cpumask API into new oneKOSAKI Motohiro2-7/+7
Adapt new API. Almost change is trivial. Most important change is the below line because we plan to change task->cpus_allowed implementation. - ctx->cpus_allowed = current->cpus_allowed; Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-05-04powerpc: Save Come-From Address Register (CFAR) in exception framePaul Mackerras4-5/+16
Recent 64-bit server processors (POWER6 and POWER7) have a "Come-From Address Register" (CFAR), that records the address of the most recent branch or rfid (return from interrupt) instruction for debugging purposes. This saves the value of the CFAR in the exception entry code and stores it in the exception frame. We also make xmon print the CFAR value in its register dump code. Rather than extend the pt_regs struct at this time, we steal the orig_gpr3 field, which is only used for system calls, and use it for the CFAR value for all exceptions/interrupts other than system calls. This means we don't save the CFAR on system calls, which is not a great problem since system calls tend not to happen unexpectedly, and also avoids adding the overhead of reading the CFAR to the system call entry path. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-05-04powerpc: Save register r9-r13 values accurately on interrupt with bad stackPaul Mackerras1-3/+4
When we take an interrupt or exception from kernel mode and the stack pointer is obviously not a kernel address (i.e. the top bit is 0), we switch to an emergency stack, save register values and panic. However, on 64-bit server machines, we don't actually save the values of r9 - r13 at the time of the interrupt, but rather values corrupted by the exception entry code for r12-r13, and nothing at all for r9-r11. This fixes it by passing a pointer to the register save area in the paca through to the bad_stack code in r3. The register values are saved in one of the paca register save areas (depending on which exception this is). Using the pointer in r3, the bad_stack code now retrieves the saved values of r9 - r13 and stores them in the exception frame on the emergency stack. This also stores the normal exception frame marker ("regshere") in the exception frame. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-05-04powerpc: Add Initiate Coprocessor Store Word (icswx) supportTseng-Hui (Frank) Lin4-1/+20
Icswx is a PowerPC instruction to send data to a co-processor. On Book-S processors the LPAR_ID and process ID (PID) of the owning process are registered in the window context of the co-processor at initialization time. When the icswx instruction is executed the L2 generates a cop-reg transaction on PowerBus. The transaction has no address and the processor does not perform an MMU access to authenticate the transaction. The co-processor compares the LPAR_ID and the PID included in the transaction and the LPAR_ID and PID held in the window context to determine if the process is authorized to generate the transaction. The OS needs to assign a 16-bit PID for the process. This cop-PID needs to be updated during context switch. The cop-PID needs to be destroyed when the context is destroyed. Signed-off-by: Sonny Rao <sonnyrao@linux.vnet.ibm.com> Signed-off-by: Tseng-Hui (Frank) Lin <thlin@linux.vnet.ibm.com> Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-05-04powerpc: Use new CPU feature bit to select 2.06 tlbieMichael Neuling2-7/+14
This removes MMU_FTR_TLBIE_206 as we can now use CPU_FTR_HVMODE_206. It also changes the logic to select which tlbie to use to be based on this new CPU feature bit. This also duplicates the ASM_FTR_IF/SET/CLR defines for CPU features (copied from MMU features). Signed-off-by: Michael Neuling <mikey@neuling.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-05-04powerpc/irq: Stop exporting irq_mapGrant Likely1-18/+3
First step in eliminating irq_map[] table entirely Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-05-02Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6Linus Torvalds1-2/+2
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6: (47 commits) sysctl: net: call unregister_net_sysctl_table where needed Revert: veth: remove unneeded ifname code from veth_newlink() smsc95xx: fix reset check tg3: Fix failure to enable WoL by default when possible networking: inappropriate ioctl operation should return ENOTTY amd8111e: trivial typo spelling: Negotitate -> Negotiate ipv4: don't spam dmesg with "Using LC-trie" messages af_unix: Only allow recv on connected seqpacket sockets. mii: add support of pause frames in mii_get_an net: ftmac100: fix scheduling while atomic during PHY link status change usbnet: Transfer of maintainership usbnet: add support for some Huawei modems with cdc-ether ports bnx2: cancel timer on device removal iwl4965: fix "Received BA when not expected" iwlagn: fix "Received BA when not expected" dsa/mv88e6131: fix unknown multicast/broadcast forwarding on mv88e6085 usbnet: Resubmit interrupt URB if device is open iwl4965: fix "TX Power requested while scanning" iwlegacy: led stay solid on when no traffic b43: trivial: update module info about ucode16_mimo firmware ...
2011-04-26Revert wrong fixes for common misspellingsLucas De Marchi1-1/+1
These changes were incorrectly fixed by codespell. They were now manually corrected. Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
2011-04-27powerpc: Free up some CPU feature bits by moving out MMU-related featuresMatt Evans3-24/+63
Some of the 64bit PPC CPU features are MMU-related, so this patch moves them to MMU_FTR_ bits. All cpu_has_feature()-style tests are moved to mmu_has_feature(), and seven feature bits are freed as a result. Signed-off-by: Matt Evans <matt@ozlabs.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-27powerpc/book3e: Fix extlb sizeMichael Ellerman1-1/+2
The calculation of the size for the exception save area of the TLB miss handler is wrong, luckily it's too big not too small. Rework it to make it a bit clearer, and also correct. We want 3 save areas, each EX_TLB_SIZE _bytes_. Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Acked-by: Kumar Gala <galak@kernel.crashing.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-27powerpc: Add MSR_64BITMichael Ellerman2-4/+12
The MSR bit which indicates 64-bit-ness is different between server and booke, so add a #define which gives you the right mask regardless. Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-27powerpc/pci: Make IO workarounds init implicit when first bus is registeredMichael Ellerman1-1/+0
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-27powerpc/pci: Move IO workarounds to the common kernel dirMichael Ellerman1-0/+49
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-27powerpc/pci: Split IO vs MMIO indirect access hooksMichael Ellerman1-5/+11
The goal is to avoid adding overhead to MMIO when only PIO is needed Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-27powerpc: Per process DSCR + some fixes (try#4)Alexey Kardashevskiy3-0/+12
The DSCR (aka Data Stream Control Register) is supported on some server PowerPC chips and allow some control over the prefetch of data streams. This patch allows the value to be specified per thread by emulating the corresponding mfspr and mtspr instructions. Children of such threads inherit the value. Other threads use a default value that can be specified in sysfs - /sys/devices/system/cpu/dscr_default. If a thread starts with non default value in the sysfs entry, all children threads inherit this non default value even if the sysfs value is changed later. Signed-off-by: Alexey Kardashevskiy <aik@au1.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-27powerpc/book3e: Flush IPROT protected TLB entries leftover by firmwareJack Miller1-0/+1
When we set up the TLB for ourselves on Book3E, we need to flush out any old mappings established by the firmware or bootloader. At present we attempt this with a tlbilx to flush everything, but this will leave behind any entries with the IPROT bit set. There are several good reason firmware might establish mappings with IPROT, and in fact ePAPR compliant firmwares are required to establish their initial mapped area with IPROT. This patch, therefore adds more complex code to scan through the TLB upon entry and flush away any entries that are not our own. Signed-off-by: Jack Miller <jack@codezen.org> Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-27powerpc: Add TLB size detection for TYPE_3E MMUsBenjamin Herrenschmidt1-0/+15
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-27powerpc: Add A2 cpu supportBenjamin Herrenschmidt2-2/+162
Add the cputable entry, regs and setup & restore entries for the PowerPC A2 core. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-21powerpc: Fix multicast problem in fs_enet driverAndrea Galbusera1-2/+2
mac-fec.c was setting individual UDP address registers instead of multicast group address registers when joining a multicast group. This prevented from correctly receiving UDP multicast packets. According to datasheet, replaced hash_table_high and hash_table_low with grp_hash_table_high and grp_hash_table_low respectively. Also renamed hash_table_* with grp_hash_table_* in struct fec declaration for 8xx: these registers are used only for multicast there. Tested on a MPC5121 based board. Build tested also against mpc866_ads_defconfig. Signed-off-by: Andrea Galbusera <gizero@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2011-04-20powerpc/xics: Move irq_host matching into the ics backendMichael Ellerman1-0/+1
An upcoming new ics backend will need to implement different matching semantics to the current ones, which are essentially the RTAS ics backends. So move the current match into the RTAS backend, and allow other ics backends to override. Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc: Add SCOM infrastructureBenjamin Herrenschmidt1-0/+156
SCOM is a side-band configuration bus implemented on some processors. This code provides a way for code to map and operate on devices via SCOM, while the details of how that is implemented is left up to a SCOM "controller" in the platform code. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc/xics: xics.h relies on linux/interrupt.hMichael Ellerman1-0/+2
Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc/a2: Add some #defines for A2 specific instructionsBenjamin Herrenschmidt1-0/+25
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc/smp: smp_ops->kick_cpu() should be able to failMichael Ellerman2-2/+2
When we start a cpu we use smp_ops->kick_cpu(), which currently returns void, it should be able to fail. Convert it to return int, and update all uses. Convert all the current error cases to return -ENOENT, which is what would eventually be returned by __cpu_up() currently when it doesn't detect the cpu as coming up in time. Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc/mm: Fix slice state initialization for Book3EMichael Ellerman1-1/+1
On Book3E, MMU_NO_CONTEXT != 0, but the slice_mm_new_context() macro assumes that it is. This means that the map of the page sizes for each slice is always initialized to zeroes (which happens to be 4k pages), rather than to the correct default base page size value - which might be 64k. This patch corrects the problem. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc/mm: Standardise on MMU_NO_CONTEXTMichael Ellerman1-0/+2
Use MMU_NO_CONTEXT as the initialiser for mm_context.id on nohash and hash64. Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc: Add NAP mode support on Power7 in HV modeBenjamin Herrenschmidt3-1/+8
Wakeup comes from the system reset handler with a potential loss of the non-hypervisor CPU state. We save the non-volatile state on the stack and a pointer to it in the PACA, which the system reset handler uses to restore things Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc: Properly handshake CPUs going out of boot spin loopBenjamin Herrenschmidt1-0/+1
We need to wait a bit for them to have done their CPU setup or we might end up with translation and EE on with different LPCR values between threads Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc: Always use SPRN_SPRG_HSCRATCH0 when running in HV modePaul Mackerras2-8/+21
This uses feature sections to arrange that we always use HSPRG1 as the scratch register in the interrupt entry code rather than SPRG2 when we're running in hypervisor mode on POWER7. This will ensure that we don't trash the guest's SPRG2 when we are running KVM guests. To simplify the code, we define GET_SCRATCH0() and SET_SCRATCH0() macros like the GET_PACA/SET_PACA macros. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc: More work to support HV exceptionsBenjamin Herrenschmidt2-14/+25
Rework exception macros a bit to split offset from vector and add some basic support for HDEC, HDSI, HISI and a few more. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc: Base support for exceptions using HSRR0/1Benjamin Herrenschmidt3-32/+35
Pass the register type to the prolog, also provides alternate "HV" version of hardware interrupt (0x500) and adjust LPES accordingly We tag those interrupts by setting bit 0x2 in the trap number Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc: In HV mode, use HSPRG0 for PACABenjamin Herrenschmidt2-4/+29
When running in Hypervisor mode (arch 2.06 or later), we store the PACA in HSPRG0 instead of SPRG1. The architecture specifies that SPRGs may be lost during a "nap" power management operation (though they aren't currently on POWER7) and this enables use of SPRG1 by KVM guests. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc: Define CPU feature for Architected 2.06 HV modeBenjamin Herrenschmidt1-1/+2
This bit indicates that we are operating in hypervisor mode on a CPU compliant to architecture 2.06 or later (currently server only). We set it on POWER7 and have a boot-time CPU setup function that clears it if MSR:HV isn't set (booting under a hypervisor). Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc: Add more Power7 specific definitionsBenjamin Herrenschmidt2-1/+46
This adds more SPR definitions used on newer processors when running in hypervisor mode. Along with some other P7 specific bits and pieces Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-20powerpc/xics: Rewrite XICS driverBenjamin Herrenschmidt2-0/+145
This is a significant rework of the XICS driver, too significant to conveniently break it up into a series of smaller patches to be honest. The driver is moved to a more generic location to allow new platforms to use it, and is broken up into separate ICP and ICS "backends". For now we have the native and "hypervisor" ICP backends and one common RTAS ICS backend. The driver supports one ICP backend instanciation, and many ICS ones, in order to accomodate future platforms with multiple possibly different interrupt "sources" mechanisms. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-18powerpc: Don't write protect kernel text with CONFIG_DYNAMIC_FTRACE enabledStefan Roese1-1/+1
This problem was noticed on an MPC855T platform. Ftrace did oops when trying to write to the kernel text segment. Many thanks to Joakim for finding the root cause of this problem. Signed-off-by: Stefan Roese <sr@denx.de> Cc: Joakim Tjernlund <joakim.tjernlund@transmode.se> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-18Merge remote branch 'kumar/merge' into mergeBenjamin Herrenschmidt1-2/+14
2011-04-12powerpc/e500mc: Remove CPU_FTR_MAYBE_CAN_NAP/CPU_FTR_MAYBE_CAN_DOZEScott Wood1-2/+1
e500mc does not support the HID0/MSR mechanism that is used by e500_idle (and there are also issues with waking on certain types of interrupts). Further, even if napping is never actually enabled, just having CPU_FTR_CAN_NAP will cause machine_init() to overwrite the board's supplied ppc_md.power_save(). We drop CPU_FTR_MAYBE_CAN_DOZE becuase we should use 'wait' instead on e500mc. Signed-off-by: Scott Wood <scottwood@freescale.com> Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
2011-04-12powerpc/book3e: Fix CPU feature handling on 64-bit e5500Kumar Gala1-0/+13
The CPU_FTRS_POSSIBLE and CPU_FTRS_ALWAYS defines did not encompass e5500 CPU features when built for 64-bit. This causes issues with cpu_has_feature() as it utilizes the POSSIBLE & ALWAYS defines as part of its check. Create a unique CPU_FTRS_E5500 (as its different from CPU_FTRS_E500MC), created a new group for 64-bit Book3e based CPUs and add CPU_FTRS_E5500 to that group. Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
2011-04-07Merge branch 'for-linus2' of git://git.profusion.mobi/users/lucas/linux-2.6Linus Torvalds16-19/+19
* 'for-linus2' of git://git.profusion.mobi/users/lucas/linux-2.6: Fix common misspellings
2011-04-01powerpc/smp: Don't expose per-cpu "cpu_state" arrayBenjamin Herrenschmidt1-1/+1
Instead, keep it static, expose an accessor and use that from the PowerMac code. Avoids easy namespace collisions and will make it easier to consolidate with other implementations. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-01powerpc/smp: Add a smp_ops->bringup_up() done callbackBenjamin Herrenschmidt1-0/+1
This allows us to stop abusing smp_ops->setup_cpu() for cleanup tasks that have to take place after the initial boot time CPU bringup. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-01powerpc/pmac/smp: Properly NAP offlined CPU on G5Benjamin Herrenschmidt1-1/+0
The current code soft-disables, and then goes to NAP mode which turns interrupts on. That means that if an interrupt occurs, we will hit the masked interrupt code path which isn't what we want, as it will return with EE off, which will either get us out of NAP mode, or fail to enter it (according to spec). Instead, let's just rely on the fact that it is safe to take decrementer interrupts on an offline CPU and leave interrupts enabled. We can also get rid of the special case in asm for power4_cpu_offline_powersave() and just use power4_idle(). Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-01powerpc/pmac/smp: Rename fixup_irqs() to migrate_irqs() and use it on ppc32Benjamin Herrenschmidt1-1/+1
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-01powerpc/pmac/smp: Fix 32-bit PowerMac cpu_dieBenjamin Herrenschmidt1-0/+1
Use generic cpu_state, call idle_task_exit() properly, and remove smp_core99_cpu_die() which isn't useful, the generic function does the job just fine.
2011-04-01powerpc/smp: Remove unused smp_ops->cpu_enable()Benjamin Herrenschmidt1-1/+0
Remove the last remnants of cpu_enable(), everybody uses the normal __cpu_up() path now Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-01powerpc/smp: Remove unused generic_cpu_enable()Benjamin Herrenschmidt1-1/+0
Nobody uses it, besides we should always use the normal __cpu_up path anyways Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-04-01powerpc/smp: soft-replugged CPUs must go back to start_secondaryBenjamin Herrenschmidt1-0/+1
Various thing are torn down when a CPU is hot-unplugged. That CPU is expected to go back to start_secondary when re-plugged to re initialize everything, such as clock sources, maps, ... Some implementations just return from cpu_die() callback in the idle loop when the CPU is "re-plugged". This is not enough. We fix it using a little asm trampoline which resets the stack and calls back into start_secondary as if we were all fresh from boot. The trampoline already existed on ppc64, but we add it for ppc32 Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>