blob: 2b47d5a863280001a24c1bc9de2924faab079ae6 [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_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 pnv_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 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);
vas_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 {
/*
* NX sees faults only with user space windows.
*/
if (window->user_win)
vas_update_csb(crb, &window->vas_win.task_ref);
else
WARN_ON_ONCE(!window->user_win);
/*
* 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;
struct vas_window *win;
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 = __pa(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);
win = vas_rx_win_open(vinst->vas_id, VAS_COP_TYPE_FAULT, &attr);
if (IS_ERR(win)) {
pr_err("VAS: Error %ld opening FaultWin\n", PTR_ERR(win));
kfree(vinst->fault_fifo);
return PTR_ERR(win);
}
vinst->fault_win = container_of(win, struct pnv_vas_window, vas_win);
pr_devel("VAS: Created FaultWin %d, LPID/PID/TID [%d/%d/%d]\n",
vinst->fault_win->vas_win.winid, attr.lnotify_lpid,
attr.lnotify_pid, attr.lnotify_tid);
return 0;
}