diff options
Diffstat (limited to 'arch/powerpc/platforms/powernv/vas-fault.c')
| -rw-r--r-- | arch/powerpc/platforms/powernv/vas-fault.c | 382 |
1 files changed, 382 insertions, 0 deletions
diff --git a/arch/powerpc/platforms/powernv/vas-fault.c b/arch/powerpc/platforms/powernv/vas-fault.c new file mode 100644 index 000000000000..25db70be4c9c --- /dev/null +++ b/arch/powerpc/platforms/powernv/vas-fault.c @@ -0,0 +1,382 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * VAS Fault handling. + * Copyright 2019, IBM Corporation + */ + +#define pr_fmt(fmt) "vas: " fmt + +#include <linux/kernel.h> +#include <linux/types.h> +#include <linux/slab.h> +#include <linux/uaccess.h> +#include <linux/kthread.h> +#include <linux/sched/signal.h> +#include <linux/mmu_context.h> +#include <asm/icswx.h> + +#include "vas.h" + +/* + * The maximum FIFO size for fault window can be 8MB + * (VAS_RX_FIFO_SIZE_MAX). Using 4MB FIFO since each VAS + * instance will be having fault window. + * 8MB FIFO can be used if expects more faults for each VAS + * instance. + */ +#define VAS_FAULT_WIN_FIFO_SIZE (4 << 20) + +static void dump_crb(struct coprocessor_request_block *crb) +{ + struct data_descriptor_entry *dde; + struct nx_fault_stamp *nx; + + dde = &crb->source; + pr_devel("SrcDDE: addr 0x%llx, len %d, count %d, idx %d, flags %d\n", + be64_to_cpu(dde->address), be32_to_cpu(dde->length), + dde->count, dde->index, dde->flags); + + dde = &crb->target; + pr_devel("TgtDDE: addr 0x%llx, len %d, count %d, idx %d, flags %d\n", + be64_to_cpu(dde->address), be32_to_cpu(dde->length), + dde->count, dde->index, dde->flags); + + nx = &crb->stamp.nx; + pr_devel("NX Stamp: PSWID 0x%x, FSA 0x%llx, flags 0x%x, FS 0x%x\n", + be32_to_cpu(nx->pswid), + be64_to_cpu(crb->stamp.nx.fault_storage_addr), + nx->flags, nx->fault_status); +} + +/* + * Update the CSB to indicate a translation error. + * + * User space will be polling on CSB after the request is issued. + * If NX can handle the request without any issues, it updates CSB. + * Whereas if NX encounters page fault, the kernel will handle the + * fault and update CSB with translation error. + * + * If we are unable to update the CSB means copy_to_user failed due to + * invalid csb_addr, send a signal to the process. + */ +static void update_csb(struct vas_window *window, + struct coprocessor_request_block *crb) +{ + struct coprocessor_status_block csb; + struct kernel_siginfo info; + struct task_struct *tsk; + void __user *csb_addr; + struct pid *pid; + int rc; + + /* + * NX user space windows can not be opened for task->mm=NULL + * and faults will not be generated for kernel requests. + */ + if (WARN_ON_ONCE(!window->mm || !window->user_win)) + return; + + csb_addr = (void __user *)be64_to_cpu(crb->csb_addr); + + memset(&csb, 0, sizeof(csb)); + csb.cc = CSB_CC_TRANSLATION; + csb.ce = CSB_CE_TERMINATION; + csb.cs = 0; + csb.count = 0; + + /* + * NX operates and returns in BE format as defined CRB struct. + * So saves fault_storage_addr in BE as NX pastes in FIFO and + * expects user space to convert to CPU format. + */ + csb.address = crb->stamp.nx.fault_storage_addr; + csb.flags = 0; + + pid = window->pid; + tsk = get_pid_task(pid, PIDTYPE_PID); + /* + * Process closes send window after all pending NX requests are + * completed. In multi-thread applications, a child thread can + * open a window and can exit without closing it. May be some + * requests are pending or this window can be used by other + * threads later. We should handle faults if NX encounters + * pages faults on these requests. Update CSB with translation + * error and fault address. If csb_addr passed by user space is + * invalid, send SEGV signal to pid saved in window. If the + * child thread is not running, send the signal to tgid. + * Parent thread (tgid) will close this window upon its exit. + * + * pid and mm references are taken when window is opened by + * process (pid). So tgid is used only when child thread opens + * a window and exits without closing it. + */ + if (!tsk) { + pid = window->tgid; + tsk = get_pid_task(pid, PIDTYPE_PID); + /* + * Parent thread (tgid) will be closing window when it + * exits. So should not get here. + */ + if (WARN_ON_ONCE(!tsk)) + return; + } + + /* Return if the task is exiting. */ + if (tsk->flags & PF_EXITING) { + put_task_struct(tsk); + return; + } + + use_mm(window->mm); + rc = copy_to_user(csb_addr, &csb, sizeof(csb)); + /* + * User space polls on csb.flags (first byte). So add barrier + * then copy first byte with csb flags update. + */ + if (!rc) { + csb.flags = CSB_V; + /* Make sure update to csb.flags is visible now */ + smp_mb(); + rc = copy_to_user(csb_addr, &csb, sizeof(u8)); + } + unuse_mm(window->mm); + put_task_struct(tsk); + + /* Success */ + if (!rc) + return; + + pr_debug("Invalid CSB address 0x%p signalling pid(%d)\n", + csb_addr, pid_vnr(pid)); + + clear_siginfo(&info); + info.si_signo = SIGSEGV; + info.si_errno = EFAULT; + info.si_code = SEGV_MAPERR; + info.si_addr = csb_addr; + + /* + * process will be polling on csb.flags after request is sent to + * NX. So generally CSB update should not fail except when an + * application passes invalid csb_addr. So an error message will + * be displayed and leave it to user space whether to ignore or + * handle this signal. + */ + rcu_read_lock(); + rc = kill_pid_info(SIGSEGV, &info, pid); + rcu_read_unlock(); + + pr_devel("%s(): pid %d kill_proc_info() rc %d\n", __func__, + pid_vnr(pid), rc); +} + +static void dump_fifo(struct vas_instance *vinst, void *entry) +{ + unsigned long *end = vinst->fault_fifo + vinst->fault_fifo_size; + unsigned long *fifo = entry; + int i; + + pr_err("Fault fifo size %d, Max crbs %d\n", vinst->fault_fifo_size, + vinst->fault_fifo_size / CRB_SIZE); + + /* Dump 10 CRB entries or until end of FIFO */ + pr_err("Fault FIFO Dump:\n"); + for (i = 0; i < 10*(CRB_SIZE/8) && fifo < end; i += 4, fifo += 4) { + pr_err("[%.3d, %p]: 0x%.16lx 0x%.16lx 0x%.16lx 0x%.16lx\n", + i, fifo, *fifo, *(fifo+1), *(fifo+2), *(fifo+3)); + } +} + +/* + * Process valid CRBs in fault FIFO. + * NX process user space requests, return credit and update the status + * in CRB. If it encounters transalation error when accessing CRB or + * request buffers, raises interrupt on the CPU to handle the fault. + * It takes credit on fault window, updates nx_fault_stamp in CRB with + * the following information and pastes CRB in fault FIFO. + * + * pswid - window ID of the window on which the request is sent. + * fault_storage_addr - fault address + * + * It can raise a single interrupt for multiple faults. Expects OS to + * process all valid faults and return credit for each fault on user + * space and fault windows. This fault FIFO control will be done with + * credit mechanism. NX can continuously paste CRBs until credits are not + * available on fault window. Otherwise, returns with RMA_reject. + * + * Total credits available on fault window: FIFO_SIZE(4MB)/CRBS_SIZE(128) + * + */ +irqreturn_t vas_fault_thread_fn(int irq, void *data) +{ + struct vas_instance *vinst = data; + struct coprocessor_request_block *crb, *entry; + struct coprocessor_request_block buf; + struct vas_window *window; + unsigned long flags; + void *fifo; + + crb = &buf; + + /* + * VAS can interrupt with multiple page faults. So process all + * valid CRBs within fault FIFO until reaches invalid CRB. + * We use CCW[0] and pswid to validate validate CRBs: + * + * CCW[0] Reserved bit. When NX pastes CRB, CCW[0]=0 + * OS sets this bit to 1 after reading CRB. + * pswid NX assigns window ID. Set pswid to -1 after + * reading CRB from fault FIFO. + * + * We exit this function if no valid CRBs are available to process. + * So acquire fault_lock and reset fifo_in_progress to 0 before + * exit. + * In case kernel receives another interrupt with different page + * fault, interrupt handler returns with IRQ_HANDLED if + * fifo_in_progress is set. Means these new faults will be + * handled by the current thread. Otherwise set fifo_in_progress + * and return IRQ_WAKE_THREAD to wake up thread. + */ + while (true) { + spin_lock_irqsave(&vinst->fault_lock, flags); + /* + * Advance the fault fifo pointer to next CRB. + * Use CRB_SIZE rather than sizeof(*crb) since the latter is + * aligned to CRB_ALIGN (256) but the CRB written to by VAS is + * only CRB_SIZE in len. + */ + fifo = vinst->fault_fifo + (vinst->fault_crbs * CRB_SIZE); + entry = fifo; + + if ((entry->stamp.nx.pswid == cpu_to_be32(FIFO_INVALID_ENTRY)) + || (entry->ccw & cpu_to_be32(CCW0_INVALID))) { + vinst->fifo_in_progress = 0; + spin_unlock_irqrestore(&vinst->fault_lock, flags); + return IRQ_HANDLED; + } + + spin_unlock_irqrestore(&vinst->fault_lock, flags); + vinst->fault_crbs++; + if (vinst->fault_crbs == (vinst->fault_fifo_size / CRB_SIZE)) + vinst->fault_crbs = 0; + + memcpy(crb, fifo, CRB_SIZE); + entry->stamp.nx.pswid = cpu_to_be32(FIFO_INVALID_ENTRY); + entry->ccw |= cpu_to_be32(CCW0_INVALID); + /* + * Return credit for the fault window. + */ + vas_return_credit(vinst->fault_win, false); + + pr_devel("VAS[%d] fault_fifo %p, fifo %p, fault_crbs %d\n", + vinst->vas_id, vinst->fault_fifo, fifo, + vinst->fault_crbs); + + dump_crb(crb); + window = vas_pswid_to_window(vinst, + be32_to_cpu(crb->stamp.nx.pswid)); + + if (IS_ERR(window)) { + /* + * We got an interrupt about a specific send + * window but we can't find that window and we can't + * even clean it up (return credit on user space + * window). + * But we should not get here. + * TODO: Disable IRQ. + */ + dump_fifo(vinst, (void *)entry); + pr_err("VAS[%d] fault_fifo %p, fifo %p, pswid 0x%x, fault_crbs %d bad CRB?\n", + vinst->vas_id, vinst->fault_fifo, fifo, + be32_to_cpu(crb->stamp.nx.pswid), + vinst->fault_crbs); + + WARN_ON_ONCE(1); + } else { + update_csb(window, crb); + /* + * Return credit for send window after processing + * fault CRB. + */ + vas_return_credit(window, true); + } + } +} + +irqreturn_t vas_fault_handler(int irq, void *dev_id) +{ + struct vas_instance *vinst = dev_id; + irqreturn_t ret = IRQ_WAKE_THREAD; + unsigned long flags; + + /* + * NX can generate an interrupt for multiple faults. So the + * fault handler thread process all CRBs until finds invalid + * entry. In case if NX sees continuous faults, it is possible + * that the thread function entered with the first interrupt + * can execute and process all valid CRBs. + * So wake up thread only if the fault thread is not in progress. + */ + spin_lock_irqsave(&vinst->fault_lock, flags); + + if (vinst->fifo_in_progress) + ret = IRQ_HANDLED; + else + vinst->fifo_in_progress = 1; + + spin_unlock_irqrestore(&vinst->fault_lock, flags); + + return ret; +} + +/* + * Fault window is opened per VAS instance. NX pastes fault CRB in fault + * FIFO upon page faults. + */ +int vas_setup_fault_window(struct vas_instance *vinst) +{ + struct vas_rx_win_attr attr; + + vinst->fault_fifo_size = VAS_FAULT_WIN_FIFO_SIZE; + vinst->fault_fifo = kzalloc(vinst->fault_fifo_size, GFP_KERNEL); + if (!vinst->fault_fifo) { + pr_err("Unable to alloc %d bytes for fault_fifo\n", + vinst->fault_fifo_size); + return -ENOMEM; + } + + /* + * Invalidate all CRB entries. NX pastes valid entry for each fault. + */ + memset(vinst->fault_fifo, FIFO_INVALID_ENTRY, vinst->fault_fifo_size); + vas_init_rx_win_attr(&attr, VAS_COP_TYPE_FAULT); + + attr.rx_fifo_size = vinst->fault_fifo_size; + attr.rx_fifo = vinst->fault_fifo; + + /* + * Max creds is based on number of CRBs can fit in the FIFO. + * (fault_fifo_size/CRB_SIZE). If 8MB FIFO is used, max creds + * will be 0xffff since the receive creds field is 16bits wide. + */ + attr.wcreds_max = vinst->fault_fifo_size / CRB_SIZE; + attr.lnotify_lpid = 0; + attr.lnotify_pid = mfspr(SPRN_PID); + attr.lnotify_tid = mfspr(SPRN_PID); + + vinst->fault_win = vas_rx_win_open(vinst->vas_id, VAS_COP_TYPE_FAULT, + &attr); + + if (IS_ERR(vinst->fault_win)) { + pr_err("VAS: Error %ld opening FaultWin\n", + PTR_ERR(vinst->fault_win)); + kfree(vinst->fault_fifo); + return PTR_ERR(vinst->fault_win); + } + + pr_devel("VAS: Created FaultWin %d, LPID/PID/TID [%d/%d/%d]\n", + vinst->fault_win->winid, attr.lnotify_lpid, + attr.lnotify_pid, attr.lnotify_tid); + + return 0; +} |