[PATCH v5 13/17] powerpc/pseries/vas: Setup IRQ and fault handling

[Haren Myneni <haren@linux.ibm.com>]

NX generates an interrupt when sees a fault on the user space
buffer and the hypervisor forwards that interrupt to OS. Then
the kernel handles the interrupt by issuing H_GET_NX_FAULT hcall
to retrieve the fault CRB information.

This patch also adds changes to setup and free IRQ per each
window and also handles the fault by updating the CSB.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
---
 arch/powerpc/platforms/pseries/vas.c | 108 +++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)

diff --git a/arch/powerpc/platforms/pseries/vas.c b/arch/powerpc/platforms/pseries/vas.c
index fe375f7a7029..55185bdd3776 100644
--- a/arch/powerpc/platforms/pseries/vas.c
+++ b/arch/powerpc/platforms/pseries/vas.c
@@ -11,6 +11,7 @@
 #include <linux/types.h>
 #include <linux/delay.h>
 #include <linux/slab.h>
+#include <linux/interrupt.h>
 #include <asm/machdep.h>
 #include <asm/hvcall.h>
 #include <asm/plpar_wrappers.h>
@@ -190,6 +191,58 @@ int h_query_vas_capabilities(const u64 hcall, u8 query_type, u64 result)
 }
 EXPORT_SYMBOL_GPL(h_query_vas_capabilities);
 
+/*
+ * hcall to get fault CRB from pHyp.
+ */
+static int h_get_nx_fault(u32 winid, u64 buffer)
+{
+	long rc;
+
+	rc = plpar_hcall_norets(H_GET_NX_FAULT, winid, buffer);
+
+	switch (rc) {
+	case H_SUCCESS:
+		return 0;
+	case H_PARAMETER:
+		pr_err("HCALL(%x): Invalid window ID %u\n", H_GET_NX_FAULT,
+		       winid);
+		return -EINVAL;
+	case H_PRIVILEGE:
+		pr_err("HCALL(%x): Window(%u): Invalid fault buffer 0x%llx\n",
+		       H_GET_NX_FAULT, winid, buffer);
+		return -EACCES;
+	default:
+		pr_err("HCALL(%x): Failed with error %ld for window(%u)\n",
+		       H_GET_NX_FAULT, rc, winid);
+		return -EIO;
+	}
+}
+
+/*
+ * Handle the fault interrupt.
+ * When the fault interrupt is received for each window, query pHyp to get
+ * the fault CRB on the specific fault. Then process the CRB by updating
+ * CSB or send signal if the user space CSB is invalid.
+ * Note: pHyp forwards an interrupt for each fault request. So one fault
+ *	CRB to process for each H_GET_NX_FAULT HCALL.
+ */
+irqreturn_t pseries_vas_fault_thread_fn(int irq, void *data)
+{
+	struct pseries_vas_window *txwin = data;
+	struct coprocessor_request_block crb;
+	struct vas_user_win_ref *tsk_ref;
+	int rc;
+
+	rc = h_get_nx_fault(txwin->vas_win.winid, (u64)virt_to_phys(&crb));
+	if (!rc) {
+		tsk_ref = &txwin->vas_win.task_ref;
+		vas_dump_crb(&crb);
+		vas_update_csb(&crb, tsk_ref);
+	}
+
+	return IRQ_HANDLED;
+}
+
 /*
  * Allocate window and setup IRQ mapping.
  */
@@ -201,10 +254,51 @@ static int allocate_setup_window(struct pseries_vas_window *txwin,
 	rc = h_allocate_vas_window(txwin, domain, wintype, DEF_WIN_CREDS);
 	if (rc)
 		return rc;
+	/*
+	 * On powerVM, pHyp setup and forwards the fault interrupt per
+	 * window. So the IRQ setup and fault handling will be done for
+	 * each open window separately.
+	 */
+	txwin->fault_virq = irq_create_mapping(NULL, txwin->fault_irq);
+	if (!txwin->fault_virq) {
+		pr_err("Failed irq mapping %d\n", txwin->fault_irq);
+		rc = -EINVAL;
+		goto out_win;
+	}
+
+	txwin->name = kasprintf(GFP_KERNEL, "vas-win-%d",
+				txwin->vas_win.winid);
+	if (!txwin->name) {
+		rc = -ENOMEM;
+		goto out_irq;
+	}
+
+	rc = request_threaded_irq(txwin->fault_virq, NULL,
+				  pseries_vas_fault_thread_fn, IRQF_ONESHOT,
+				  txwin->name, txwin);
+	if (rc) {
+		pr_err("VAS-Window[%d]: Request IRQ(%u) failed with %d\n",
+		       txwin->vas_win.winid, txwin->fault_virq, rc);
+		goto out_free;
+	}
 
 	txwin->vas_win.wcreds_max = DEF_WIN_CREDS;
 
 	return 0;
+out_free:
+	kfree(txwin->name);
+out_irq:
+	irq_dispose_mapping(txwin->fault_virq);
+out_win:
+	h_deallocate_vas_window(txwin->vas_win.winid);
+	return rc;
+}
+
+static inline void free_irq_setup(struct pseries_vas_window *txwin)
+{
+	free_irq(txwin->fault_virq, txwin);
+	irq_dispose_mapping(txwin->fault_virq);
+	kfree(txwin->name);
 }
 
 static struct vas_window *vas_allocate_window(struct vas_tx_win_open_attr *uattr,
@@ -320,6 +414,11 @@ static struct vas_window *vas_allocate_window(struct vas_tx_win_open_attr *uattr
 	return &txwin->vas_win;
 
 out_free:
+	/*
+	 * Window is not operational. Free IRQ before closing
+	 * window so that do not have to hold mutex.
+	 */
+	free_irq_setup(txwin);
 	h_deallocate_vas_window(txwin->vas_win.winid);
 out:
 	atomic_dec(&ct_caps->used_lpar_creds);
@@ -339,7 +438,16 @@ static int deallocate_free_window(struct pseries_vas_window *win)
 {
 	int rc = 0;
 
+	/*
+	 * Free IRQ after executing H_DEALLOCATE_VAS_WINDOW HCALL
+	 * to close the window. pHyp waits for all requests including
+	 * faults are processed before closing the window - Means all
+	 * credits are returned. In the case of fault request, credit
+	 * is returned after OS issues H_GET_NX_FAULT HCALL.
+	 */
 	rc = h_deallocate_vas_window(win->vas_win.winid);
+	if (!rc)
+		free_irq_setup(win);
 
 	return rc;
 }
-- 
2.18.2