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Diffstat (limited to 'kernel/arch/powerpc/mm/icswx.c')
| -rw-r--r-- | kernel/arch/powerpc/mm/icswx.c | 292 |
1 files changed, 292 insertions, 0 deletions
diff --git a/kernel/arch/powerpc/mm/icswx.c b/kernel/arch/powerpc/mm/icswx.c new file mode 100644 index 000000000..915412e4d --- /dev/null +++ b/kernel/arch/powerpc/mm/icswx.c @@ -0,0 +1,292 @@ +/* + * ICSWX and ACOP Management + * + * Copyright (C) 2011 Anton Blanchard, IBM Corp. <anton@samba.org> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + * + */ + +#include <linux/sched.h> +#include <linux/kernel.h> +#include <linux/errno.h> +#include <linux/types.h> +#include <linux/mm.h> +#include <linux/spinlock.h> +#include <linux/module.h> +#include <linux/uaccess.h> + +#include "icswx.h" + +/* + * The processor and its L2 cache cause the icswx instruction to + * generate a COP_REQ transaction on PowerBus. The transaction has no + * address, and the processor does not perform an MMU access to + * authenticate the transaction. The command portion of the PowerBus + * COP_REQ transaction includes the LPAR_ID (LPID) and the coprocessor + * Process ID (PID), which the coprocessor compares to the authorized + * LPID and PID held in the coprocessor, to determine if the process + * is authorized to generate the transaction. The data of the COP_REQ + * transaction is 128-byte or less in size and is placed in cacheable + * memory on a 128-byte cache line boundary. + * + * The task to use a coprocessor should use use_cop() to mark the use + * of the Coprocessor Type (CT) and context switching. On a server + * class processor, the PID register is used only for coprocessor + * management + * and so a coprocessor PID is allocated before + * executing icswx + * instruction. Drop_cop() is used to free the + * coprocessor PID. + * + * Example: + * Host Fabric Interface (HFI) is a PowerPC network coprocessor. + * Each HFI have multiple windows. Each HFI window serves as a + * network device sending to and receiving from HFI network. + * HFI immediate send function uses icswx instruction. The immediate + * send function allows small (single cache-line) packets be sent + * without using the regular HFI send FIFO and doorbell, which are + * much slower than immediate send. + * + * For each task intending to use HFI immediate send, the HFI driver + * calls use_cop() to obtain a coprocessor PID for the task. + * The HFI driver then allocate a free HFI window and save the + * coprocessor PID to the HFI window to allow the task to use the + * HFI window. + * + * The HFI driver repeatedly creates immediate send packets and + * issues icswx instruction to send data through the HFI window. + * The HFI compares the coprocessor PID in the CPU PID register + * to the PID held in the HFI window to determine if the transaction + * is allowed. + * + * When the task to release the HFI window, the HFI driver calls + * drop_cop() to release the coprocessor PID. + */ + +void switch_cop(struct mm_struct *next) +{ +#ifdef CONFIG_PPC_ICSWX_PID + mtspr(SPRN_PID, next->context.cop_pid); +#endif + mtspr(SPRN_ACOP, next->context.acop); +} + +/** + * Start using a coprocessor. + * @acop: mask of coprocessor to be used. + * @mm: The mm the coprocessor to associate with. Most likely current mm. + * + * Return a positive PID if successful. Negative errno otherwise. + * The returned PID will be fed to the coprocessor to determine if an + * icswx transaction is authenticated. + */ +int use_cop(unsigned long acop, struct mm_struct *mm) +{ + int ret; + + if (!cpu_has_feature(CPU_FTR_ICSWX)) + return -ENODEV; + + if (!mm || !acop) + return -EINVAL; + + /* The page_table_lock ensures mm_users won't change under us */ + spin_lock(&mm->page_table_lock); + spin_lock(mm->context.cop_lockp); + + ret = get_cop_pid(mm); + if (ret < 0) + goto out; + + /* update acop */ + mm->context.acop |= acop; + + sync_cop(mm); + + /* + * If this is a threaded process then there might be other threads + * running. We need to send an IPI to force them to pick up any + * change in PID and ACOP. + */ + if (atomic_read(&mm->mm_users) > 1) + smp_call_function(sync_cop, mm, 1); + +out: + spin_unlock(mm->context.cop_lockp); + spin_unlock(&mm->page_table_lock); + + return ret; +} +EXPORT_SYMBOL_GPL(use_cop); + +/** + * Stop using a coprocessor. + * @acop: mask of coprocessor to be stopped. + * @mm: The mm the coprocessor associated with. + */ +void drop_cop(unsigned long acop, struct mm_struct *mm) +{ + int free_pid; + + if (!cpu_has_feature(CPU_FTR_ICSWX)) + return; + + if (WARN_ON_ONCE(!mm)) + return; + + /* The page_table_lock ensures mm_users won't change under us */ + spin_lock(&mm->page_table_lock); + spin_lock(mm->context.cop_lockp); + + mm->context.acop &= ~acop; + + free_pid = disable_cop_pid(mm); + sync_cop(mm); + + /* + * If this is a threaded process then there might be other threads + * running. We need to send an IPI to force them to pick up any + * change in PID and ACOP. + */ + if (atomic_read(&mm->mm_users) > 1) + smp_call_function(sync_cop, mm, 1); + + if (free_pid != COP_PID_NONE) + free_cop_pid(free_pid); + + spin_unlock(mm->context.cop_lockp); + spin_unlock(&mm->page_table_lock); +} +EXPORT_SYMBOL_GPL(drop_cop); + +static int acop_use_cop(int ct) +{ + /* There is no alternate policy, yet */ + return -1; +} + +/* + * Get the instruction word at the NIP + */ +static u32 acop_get_inst(struct pt_regs *regs) +{ + u32 inst; + u32 __user *p; + + p = (u32 __user *)regs->nip; + if (!access_ok(VERIFY_READ, p, sizeof(*p))) + return 0; + + if (__get_user(inst, p)) + return 0; + + return inst; +} + +/** + * @regs: regsiters at time of interrupt + * @address: storage address + * @error_code: Fault code, usually the DSISR or ESR depending on + * processor type + * + * Return 0 if we are able to resolve the data storage fault that + * results from a CT miss in the ACOP register. + */ +int acop_handle_fault(struct pt_regs *regs, unsigned long address, + unsigned long error_code) +{ + int ct; + u32 inst = 0; + + if (!cpu_has_feature(CPU_FTR_ICSWX)) { + pr_info("No coprocessors available"); + _exception(SIGILL, regs, ILL_ILLOPN, address); + } + + if (!user_mode(regs)) { + /* this could happen if the HV denies the + * kernel access, for now we just die */ + die("ICSWX from kernel failed", regs, SIGSEGV); + } + + /* Some implementations leave us a hint for the CT */ + ct = ICSWX_GET_CT_HINT(error_code); + if (ct < 0) { + /* we have to peek at the instruction word to figure out CT */ + u32 ccw; + u32 rs; + + inst = acop_get_inst(regs); + if (inst == 0) + return -1; + + rs = (inst >> (31 - 10)) & 0x1f; + ccw = regs->gpr[rs]; + ct = (ccw >> 16) & 0x3f; + } + + /* + * We could be here because another thread has enabled acop + * but the ACOP register has yet to be updated. + * + * This should have been taken care of by the IPI to sync all + * the threads (see smp_call_function(sync_cop, mm, 1)), but + * that could take forever if there are a significant amount + * of threads. + * + * Given the number of threads on some of these systems, + * perhaps this is the best way to sync ACOP rather than whack + * every thread with an IPI. + */ + if ((acop_copro_type_bit(ct) & current->active_mm->context.acop) != 0) { + sync_cop(current->active_mm); + return 0; + } + + /* check for alternate policy */ + if (!acop_use_cop(ct)) + return 0; + + /* at this point the CT is unknown to the system */ + pr_warn("%s[%d]: Coprocessor %d is unavailable\n", + current->comm, current->pid, ct); + + /* get inst if we don't already have it */ + if (inst == 0) { + inst = acop_get_inst(regs); + if (inst == 0) + return -1; + } + + /* Check if the instruction is the "record form" */ + if (inst & 1) { + /* + * the instruction is "record" form so we can reject + * using CR0 + */ + regs->ccr &= ~(0xful << 28); + regs->ccr |= ICSWX_RC_NOT_FOUND << 28; + + /* Move on to the next instruction */ + regs->nip += 4; + } else { + /* + * There is no architected mechanism to report a bad + * CT so we could either SIGILL or report nothing. + * Since the non-record version should only bu used + * for "hints" or "don't care" we should probably do + * nothing. However, I could see how some people + * might want an SIGILL so it here if you want it. + */ +#ifdef CONFIG_PPC_ICSWX_USE_SIGILL + _exception(SIGILL, regs, ILL_ILLOPN, address); +#else + regs->nip += 4; +#endif + } + + return 0; +} +EXPORT_SYMBOL_GPL(acop_handle_fault); |