blob: 3d21fce254b741c3b7bb52edcea631108d42aa9c [file] [log] [blame]
// 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_FAULT_ADDRESS;
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;
}
kthread_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));
}
kthread_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;
}