From b94341afcb12dac74825ac6fb140e2819760b00d Mon Sep 17 00:00:00 2001
From: Elliott Mitchell <ehem+freebsd@m5p.com>
Date: Mon, 31 May 2021 18:34:33 -0700
Subject: [PATCH] xen/intr: rework xen_intr_resume() for in-place remapping

The prior implementation of xen_intr_resume() was wiping
xen_intr_port_to_isrc[] and then rebuilding from the x86 interrupt
table.  Rework to instead wipe the channel numbers (->xi_port) and then
scan the table for sources with invalid channels.

This will be slower due to scanning the whole table, but this removes
the dependency on the x86 interrupt code.

Reviewed by: royger
Differential Revision: https://reviews.freebsd.org/D30599
[royger]
Split line over 80 characters.
---
 sys/x86/xen/xen_intr.c | 41 +++++++++++++++++++++++++++--------------
 1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/sys/x86/xen/xen_intr.c b/sys/x86/xen/xen_intr.c
index e2f23b4a5c6e..4b9b4675b5a0 100644
--- a/sys/x86/xen/xen_intr.c
+++ b/sys/x86/xen/xen_intr.c
@@ -729,13 +729,14 @@ xen_rebind_virq(struct xenisrc *isrc)
 	isrc->xi_port = bind_virq.port;
 }
 
-static void
+static struct xenisrc *
 xen_intr_rebind_isrc(struct xenisrc *isrc)
 {
 #ifdef SMP
 	u_int cpu = isrc->xi_cpu;
 	int error;
 #endif
+	struct xenisrc *prev;
 
 	switch (isrc->xi_type) {
 	case EVTCHN_TYPE_IPI:
@@ -745,9 +746,10 @@ xen_intr_rebind_isrc(struct xenisrc *isrc)
 		xen_rebind_virq(isrc);
 		break;
 	default:
-		return;
+		return (NULL);
 	}
 
+	prev = xen_intr_port_to_isrc[isrc->xi_port];
 	xen_intr_port_to_isrc[isrc->xi_port] = isrc;
 
 #ifdef SMP
@@ -760,6 +762,8 @@ xen_intr_rebind_isrc(struct xenisrc *isrc)
 #endif
 
 	evtchn_unmask_port(isrc->xi_port);
+
+	return (prev);
 }
 
 /**
@@ -769,7 +773,6 @@ static void
 xen_intr_resume(struct pic *unused, bool suspend_cancelled)
 {
 	shared_info_t *s = HYPERVISOR_shared_info;
-	struct xenisrc *isrc;
 	u_int isrc_idx;
 	int i;
 
@@ -789,19 +792,29 @@ xen_intr_resume(struct pic *unused, bool suspend_cancelled)
 	for (i = 0; i < nitems(s->evtchn_mask); i++)
 		atomic_store_rel_long(&s->evtchn_mask[i], ~0);
 
-	/* Remove port -> isrc mappings */
-	memset(xen_intr_port_to_isrc, 0, sizeof(xen_intr_port_to_isrc));
+	/* Clear existing port mappings */
+	for (isrc_idx = 0; isrc_idx < NR_EVENT_CHANNELS; ++isrc_idx)
+		if (xen_intr_port_to_isrc[isrc_idx] != NULL)
+			xen_intr_port_to_isrc[isrc_idx]->xi_port =
+			    INVALID_EVTCHN;
 
-	/* Free unused isrcs and rebind VIRQs and IPIs */
-	for (isrc_idx = 0; isrc_idx < xen_intr_auto_vector_count; isrc_idx++) {
-		u_int vector;
+	/* Remap in-use isrcs, using xen_intr_port_to_isrc as listing */
+	for (isrc_idx = 0; isrc_idx < NR_EVENT_CHANNELS; ++isrc_idx) {
+		struct xenisrc *cur = xen_intr_port_to_isrc[isrc_idx];
 
-		vector = first_evtchn_irq + isrc_idx;
-		isrc = (struct xenisrc *)intr_lookup_source(vector);
-		if (isrc != NULL) {
-			isrc->xi_port = INVALID_EVTCHN;
-			xen_intr_rebind_isrc(isrc);
-		}
+		/* empty or entry already taken care of */
+		if (cur == NULL || cur->xi_port == isrc_idx)
+			continue;
+
+		xen_intr_port_to_isrc[isrc_idx] = NULL;
+
+		do {
+			KASSERT(!is_valid_evtchn(cur->xi_port),
+			    ("%s(): Multiple channels on single intr?",
+			    __func__));
+
+			cur = xen_intr_rebind_isrc(cur);
+		} while (cur != NULL);
 	}
 }