[PATCH V4 06/14] powerpc/vas: Setup thread IRQ handler per VAS instance

Haren Myneni haren at linux.ibm.com
Sun Dec 22 22:14:21 AEDT 2019


Setup thread IRQ handler per each VAS instance. When NX sees a fault
on CRB, kernel gets an interrupt and vas_fault_handler will be
executed to process fault CRBs. Read all valid CRBs from fault FIFO,
determine the corresponding send window from CRB and process fault
requests.

Signed-off-by: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
Signed-off-by: Haren Myneni <haren at linux.ibm.com>
---
 arch/powerpc/platforms/powernv/vas-fault.c  | 85 +++++++++++++++++++++++++++++
 arch/powerpc/platforms/powernv/vas-window.c | 60 ++++++++++++++++++++
 arch/powerpc/platforms/powernv/vas.c        | 21 ++++++-
 arch/powerpc/platforms/powernv/vas.h        |  4 ++
 4 files changed, 169 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/powernv/vas-fault.c b/arch/powerpc/platforms/powernv/vas-fault.c
index b0258ed..5c2cada 100644
--- a/arch/powerpc/platforms/powernv/vas-fault.c
+++ b/arch/powerpc/platforms/powernv/vas-fault.c
@@ -11,6 +11,7 @@
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/kthread.h>
+#include <linux/mmu_context.h>
 #include <asm/icswx.h>
 
 #include "vas.h"
@@ -25,6 +26,90 @@
 #define VAS_FAULT_WIN_FIFO_SIZE	(4 << 20)
 
 /*
+ * Process CRBs that we receive on the fault window.
+ */
+irqreturn_t vas_fault_handler(int irq, void *data)
+{
+	struct vas_instance *vinst = data;
+	struct coprocessor_request_block buf, *crb;
+	struct vas_window *window;
+	void *fifo;
+
+	/*
+	 * VAS can interrupt with multiple page faults. So process all
+	 * valid CRBs within fault FIFO until reaches invalid CRB.
+	 * NX updates nx_fault_stamp in CRB and pastes in fault FIFO.
+	 * kernel retrives send window from parition send window ID
+	 * (pswid) in nx_fault_stamp. So pswid should be non-zero and
+	 * use this to check whether CRB is valid.
+	 * After reading CRB entry, it is reset with 0's in fault FIFO.
+	 *
+	 * In case kernel receives another interrupt with different page
+	 * fault and CRBs are processed by the previous handling, will be
+	 * returned from this function when it sees invalid CRB (means 0's).
+	 */
+	do {
+		mutex_lock(&vinst->mutex);
+
+		/*
+		 * 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);
+		crb = fifo;
+
+		/*
+		 * NX pastes nx_fault_stamp in fault FIFO for each fault.
+		 * So use pswid to check whether fault CRB is valid.
+		 * pswid returned from NX will be in _be32, but just
+		 * checking non-zero value to make sure the CRB is valid.
+		 * Return if reached invalid CRB.
+		 */
+		if (!crb->stamp.nx.pswid) {
+			mutex_unlock(&vinst->mutex);
+			return IRQ_HANDLED;
+		}
+
+		vinst->fault_crbs++;
+		if (vinst->fault_crbs == (vinst->fault_fifo_size / CRB_SIZE))
+			vinst->fault_crbs = 0;
+
+		crb = &buf;
+		memcpy(crb, fifo, CRB_SIZE);
+		memset(fifo, 0, CRB_SIZE);
+		mutex_unlock(&vinst->mutex);
+
+		pr_devel("VAS[%d] fault_fifo %p, fifo %p, fault_crbs %d\n",
+				vinst->vas_id, vinst->fault_fifo, fifo,
+				vinst->fault_crbs);
+
+		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).
+			 * But we should not get here.
+			 */
+			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);
+			return IRQ_HANDLED;
+		}
+
+	} while (true);
+
+	return IRQ_HANDLED;
+}
+
+/*
  * Fault window is opened per VAS instance. NX pastes fault CRB in fault
  * FIFO upon page faults.
  */
diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
index f07f49a..cec1b41 100644
--- a/arch/powerpc/platforms/powernv/vas-window.c
+++ b/arch/powerpc/platforms/powernv/vas-window.c
@@ -1041,6 +1041,15 @@ struct vas_window *vas_tx_win_open(int vasid, enum vas_cop_type cop,
 		}
 	} else {
 		/*
+		 * Interrupt hanlder or fault window setup failed. Means
+		 * NX can not generate fault for page fault. So not
+		 * opening for user space tx window.
+		 */
+		if (!vinst->virq) {
+			rc = -ENODEV;
+			goto free_window;
+		}
+		/*
 		 * A user mapping must ensure that context switch issues
 		 * CP_ABORT for this thread.
 		 */
@@ -1255,3 +1264,54 @@ int vas_win_close(struct vas_window *window)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(vas_win_close);
+
+struct vas_window *vas_pswid_to_window(struct vas_instance *vinst,
+		uint32_t pswid)
+{
+	int winid;
+	struct vas_window *window;
+
+	if (!pswid) {
+		pr_devel("%s: called for pswid 0!\n", __func__);
+		return ERR_PTR(-ESRCH);
+	}
+
+	decode_pswid(pswid, NULL, &winid);
+
+	if (winid >= VAS_WINDOWS_PER_CHIP)
+		return ERR_PTR(-ESRCH);
+
+	/*
+	 * If application closes the window before the hardware
+	 * returns the fault CRB, we should wait in vas_win_close()
+	 * for the pending requests. so the window must be active
+	 * and the process alive.
+	 *
+	 * If its a kernel process, we should not get any faults and
+	 * should not get here.
+	 */
+	window = vinst->windows[winid];
+
+	if (!window) {
+		pr_err("PSWID decode: Could not find window for winid %d pswid %d vinst 0x%p\n",
+			winid, pswid, vinst);
+		return NULL;
+	}
+
+	/*
+	 * Do some sanity checks on the decoded window.  Window should be
+	 * NX GZIP user send window. FTW windows should not incur faults
+	 * since their CRBs are ignored (not queued on FIFO or processed
+	 * by NX).
+	 */
+	if (!window->tx_win || !window->user_win || !window->nx_win ||
+			window->cop == VAS_COP_TYPE_FAULT ||
+			window->cop == VAS_COP_TYPE_FTW) {
+		pr_err("PSWID decode: id %d, tx %d, user %d, nx %d, cop %d\n",
+			winid, window->tx_win, window->user_win,
+			window->nx_win, window->cop);
+		WARN_ON(1);
+	}
+
+	return window;
+}
diff --git a/arch/powerpc/platforms/powernv/vas.c b/arch/powerpc/platforms/powernv/vas.c
index 557c8e4..46ea57d 100644
--- a/arch/powerpc/platforms/powernv/vas.c
+++ b/arch/powerpc/platforms/powernv/vas.c
@@ -14,6 +14,8 @@
 #include <linux/of_platform.h>
 #include <linux/of_address.h>
 #include <linux/of.h>
+#include <linux/irqdomain.h>
+#include <linux/interrupt.h>
 #include <asm/prom.h>
 #include <asm/xive.h>
 
@@ -26,7 +28,24 @@
 
 static int vas_irq_fault_window_setup(struct vas_instance *vinst)
 {
-	return vas_setup_fault_window(vinst);
+	char devname[64];
+	int rc = 0;
+
+	snprintf(devname, sizeof(devname), "vas-%d", vinst->vas_id);
+	rc = request_threaded_irq(vinst->virq, NULL, vas_fault_handler,
+					IRQF_ONESHOT, devname, vinst);
+	if (rc) {
+		pr_err("VAS[%d]: Request IRQ(%d) failed with %d\n",
+				vinst->vas_id, vinst->virq, rc);
+		goto out;
+	}
+
+	rc = vas_setup_fault_window(vinst);
+	if (rc)
+		free_irq(vinst->virq, vinst);
+
+out:
+	return rc;
 }
 
 static int init_vas_instance(struct platform_device *pdev)
diff --git a/arch/powerpc/platforms/powernv/vas.h b/arch/powerpc/platforms/powernv/vas.h
index 9f08daa..879f5b4 100644
--- a/arch/powerpc/platforms/powernv/vas.h
+++ b/arch/powerpc/platforms/powernv/vas.h
@@ -315,6 +315,7 @@ struct vas_instance {
 
 	u64 irq_port;
 	int virq;
+	int fault_crbs;
 	int fault_fifo_size;
 	void *fault_fifo;
 	struct vas_window *fault_win; /* Fault window */
@@ -413,6 +414,9 @@ struct vas_winctx {
 extern void vas_window_init_dbgdir(struct vas_window *win);
 extern void vas_window_free_dbgdir(struct vas_window *win);
 extern int vas_setup_fault_window(struct vas_instance *vinst);
+extern irqreturn_t vas_fault_handler(int irq, void *data);
+extern struct vas_window *vas_pswid_to_window(struct vas_instance *vinst,
+						uint32_t pswid);
 
 static inline void vas_log_write(struct vas_window *win, char *name,
 			void *regptr, u64 val)
-- 
1.8.3.1





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