[RFC PATCH 10/11] VAS: Create a thread to monitor fault-window
Sukadev Bhattiprolu
sukadev at linux.vnet.ibm.com
Sat Nov 12 04:02:55 AEDT 2016
The VAS hardware requires kernel to setup a "fault window" to which
the hardware will paste a CRB in case of address translation faults.
Create a fault window (which is basically a special receive window)
and a kernel thread that processes the CRBs that arrive at the fault
window. A follow-on patch will implement IRQ handling and the
interrupt handler will wake up the fault thread.
The fault window and thread will be used when we support user-space
access to the VAS/NX hardware. For now the fault window thread simply
dumps/logs the CRB and the fault isolation registers. Including these
in this RFC patchset for review/comments.
Signed-off-by: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
---
drivers/misc/vas/vas-internal.h | 1 +
drivers/misc/vas/vas.c | 157 +++++++++++++++++++++++++++++++++++++++-
2 files changed, 157 insertions(+), 1 deletion(-)
diff --git a/drivers/misc/vas/vas-internal.h b/drivers/misc/vas/vas-internal.h
index a58ffb2..e3ceb74 100644
--- a/drivers/misc/vas/vas-internal.h
+++ b/drivers/misc/vas/vas-internal.h
@@ -366,6 +366,7 @@ extern int vas_initialized;
extern int vas_window_reset(struct vas_instance *vinst, int winid);
extern struct vas_instance *find_vas_instance(int node, int chip);
+extern void vas_wakeup_fault_win_thread(void);
/*
* VREG(x):
diff --git a/drivers/misc/vas/vas.c b/drivers/misc/vas/vas.c
index 785e7a1..448d7f9 100644
--- a/drivers/misc/vas/vas.c
+++ b/drivers/misc/vas/vas.c
@@ -12,15 +12,29 @@
#include <linux/export.h>
#include <linux/types.h>
#include <linux/slab.h>
+#include <linux/kthread.h>
#include <linux/io.h>
#include <asm/vas.h>
#include "vas-internal.h"
#include <asm/opal-api.h>
#include <asm/opal.h>
+#define VAS_FAULT_WIN_FIFO_SIZE (64 << 10)
+#define VAS_FAULT_WIN_WCREDS 64
+
int vas_initialized;
struct vas_instance *vas_instances;
+struct fault_win_thread_arg {
+ int notified;
+ wait_queue_head_t wq;
+ void *rx_fifo;
+ int rx_fifo_size;
+} fwta;
+
+struct task_struct *fwt_thr; /* Fault window thread */
+struct vas_window *fault_win;
+
/*
* Read the Fault Isolation Registers (FIR) from skiboot into @fir.
*/
@@ -56,6 +70,135 @@ void vas_print_regs(int chip)
}
}
+void vas_wakeup_fault_win_thread(void)
+{
+ fwta.notified = 1;
+ wake_up(&fwta.wq);
+}
+
+/*
+ * Process a CRB that we receive on the fault window.
+ *
+ * TODO: Since we only support in-kernel compression requests for now,
+ * we should not get a fault. If we do, dump the CRB and the FIR
+ * and return - VAS may enter a checkstop :-(
+ */
+static void process_fault_crb(struct fault_win_thread_arg *fwt)
+{
+ u64 buf[16];
+
+ /* TODO: Dump FIRs for all chips for now. We should detect the
+ * current chip id and dump only for that chip?
+ */
+ vas_print_regs(-1);
+
+ memcpy(buf, fwt->rx_fifo, sizeof(buf));
+ memset(fwt->rx_fifo, 0, sizeof(buf));
+ pr_debug("VAS: FaultWin Rx-fifo: 0x%llx 0x%llx 0x%llx 0x%llx\n",
+ buf[0], buf[1], buf[2], buf[3]);
+}
+
+static int fault_win_thread(void *arg)
+{
+ struct fault_win_thread_arg *fwta = arg;
+
+ do {
+ if (signal_pending(current))
+ flush_signals(current);
+
+ fwta->notified = 0;
+ wait_event_interruptible(fwta->wq, fwta->notified ||
+ kthread_should_stop());
+
+ process_fault_crb(fwta);
+
+ } while (!kthread_should_stop());
+
+ return 0;
+}
+
+static int create_fault_win(void)
+{
+ char *name = "VAS-FaultWin-Thread";
+ struct vas_rx_win_attr attr;
+
+ init_waitqueue_head(&fwta.wq);
+ fwta.notified = 0;
+ fwta.rx_fifo_size = VAS_FAULT_WIN_FIFO_SIZE;
+ fwta.rx_fifo = kmalloc(fwta.rx_fifo_size, GFP_KERNEL);
+ if (!fwta.rx_fifo) {
+ pr_err("VAS: Unable to alloc %d bytes for rx_fifo\n",
+ fwta.rx_fifo_size);
+ return -1;
+ }
+
+ /*
+ * Create a worker thread that processes the fault CRBs.
+ */
+ fwt_thr = kthread_create_on_node(fault_win_thread, &fwta, 0, name, 0);
+ if (IS_ERR(fwt_thr))
+ goto free_mem;
+
+ memset(&attr, 0, sizeof(attr));
+ attr.rx_fifo_size = fwta.rx_fifo_size;
+ attr.rx_fifo = fwta.rx_fifo;
+
+ attr.wcreds_max = VAS_FAULT_WIN_WCREDS;
+ attr.tc_mode = VAS_THRESH_DISABLED;
+ attr.pin_win = true;
+ attr.tx_win_ord_mode = true;
+ attr.rx_win_ord_mode = true;
+ attr.fault_win = true;
+
+ /*
+ * 3.1.4.32: Local Notification Control Register. notify_disable is
+ * true and interrupt disable is false for Fault windows
+ */
+ attr.notify_disable = true;
+
+ attr.lnotify_lpid = 0;
+ attr.lnotify_pid = task_pid_nr(fwt_thr);
+ attr.lnotify_tid = task_pid_nr(fwt_thr);
+
+ fault_win = vas_rx_win_open(0, 0, VAS_COP_TYPE_FAULT, &attr);
+ if (IS_ERR(fault_win)) {
+ pr_err("VAS: Error %ld opening fault window\n",
+ PTR_ERR(fault_win));
+ goto stop_thread;
+ }
+
+ /*
+ * Wakeup fault thread after fault rx window is opened.
+ */
+ wake_up_process(fwt_thr);
+
+ pr_err("VAS: Created fault window, %d, LPID/PID/TID [%d/%d/%d]\n",
+ fault_win->winid, attr.lnotify_lpid, attr.lnotify_pid,
+ attr.lnotify_tid);
+
+ return 0;
+
+stop_thread:
+ kthread_stop(fwt_thr);
+
+free_mem:
+ kfree(attr.rx_fifo);
+ return -1;
+}
+
+static void destroy_fault_win(void)
+{
+ if (vas_win_close(fault_win) < 0)
+ pr_err("VAS: error closing fault window\n");
+
+ /*
+ * TODO: fault_win_thread() does not exit unless stopped
+ * but check if there can be any race here.
+ */
+ kthread_stop(fwt_thr);
+ kfree(fwta.rx_fifo);
+ pr_err("VAS: Fault thread stopped\n");
+}
static void init_vas_chip(struct vas_instance *vinst)
{
@@ -93,7 +236,7 @@ static void init_vas_instance(int node, int chip)
int vas_init(void)
{
- int n, c;
+ int n, c, rc;
vas_instances = kmalloc_array(VAS_MAX_NODES * VAS_MAX_CHIPS_PER_NODE,
sizeof(struct vas_instance), GFP_KERNEL);
@@ -110,12 +253,24 @@ int vas_init(void)
vas_initialized = 1;
+ /*
+ * Create fault handler thread and window.
+ */
+ rc = create_fault_win();
+ if (rc < 0)
+ goto cleanup;
+
return 0;
+
+cleanup:
+ kfree(vas_instances);
+ return rc;
}
void vas_exit(void)
{
vas_initialized = 0;
+ destroy_fault_win();
kfree(vas_instances);
}
--
1.8.3.1
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