From e82d5294934c4546a225fe4ca515799a323e432e Mon Sep 17 00:00:00 2001
From: mlarkin <mlarkin@openbsd.org>
Date: Tue, 2 May 2017 09:51:19 +0000
Subject: [PATCH] Resynchronize the guest RTC via vmmci(4) on host resume from
 zzz/ZZZ (vmd part)

This feature is for OpenBSD guests only.

ok reyk, kettenis
---
 usr.sbin/vmd/mc146818.c | 14 ++++++++++++--
 usr.sbin/vmd/virtio.c   | 23 +++++++++++++++++++++--
 usr.sbin/vmd/virtio.h   |  3 ++-
 3 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/usr.sbin/vmd/mc146818.c b/usr.sbin/vmd/mc146818.c
index ba721d27106..62601adbac3 100644
--- a/usr.sbin/vmd/mc146818.c
+++ b/usr.sbin/vmd/mc146818.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: mc146818.c,v 1.12 2017/03/27 00:28:04 deraadt Exp $ */
+/* $OpenBSD: mc146818.c,v 1.13 2017/05/02 09:51:19 mlarkin Exp $ */
 /*
  * Copyright (c) 2016 Mike Larkin <mlarkin@openbsd.org>
  *
@@ -27,8 +27,10 @@
 #include <string.h>
 #include <time.h>
 
+#include "vmd.h"
 #include "mc146818.h"
 #include "proc.h"
+#include "virtio.h"
 #include "vmm.h"
 
 #define MC_DIVIDER_MASK 0xe0
@@ -96,8 +98,16 @@ rtc_updateregs(void)
 static void
 rtc_fire1(int fd, short type, void *arg)
 {
-	rtc.now++;
+	time_t old = rtc.now;
+
+	time(&rtc.now);
+
 	rtc_updateregs();
+	if (rtc.now - old > 5) {
+		log_debug("%s: RTC clock drift (%llds), requesting guest "
+		    "resync", __func__, (rtc.now - old));
+		vmmci_ctl(VMMCI_SYNCRTC);
+	}
 	evtimer_add(&rtc.sec, &rtc.sec_tv);
 }
 
diff --git a/usr.sbin/vmd/virtio.c b/usr.sbin/vmd/virtio.c
index f84110a5301..8b496c20cd4 100644
--- a/usr.sbin/vmd/virtio.c
+++ b/usr.sbin/vmd/virtio.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: virtio.c,v 1.43 2017/04/25 16:38:23 reyk Exp $	*/
+/*	$OpenBSD: virtio.c,v 1.44 2017/05/02 09:51:19 mlarkin Exp $	*/
 
 /*
  * Copyright (c) 2015 Mike Larkin <mlarkin@openbsd.org>
@@ -58,6 +58,7 @@ int nr_vionet;
 
 #define VMMCI_F_TIMESYNC	(1<<0)
 #define VMMCI_F_ACK		(1<<1)
+#define VMMCI_F_SYNCRTC		(1<<2)
 
 const char *
 vioblk_cmd_name(uint32_t type)
@@ -1453,6 +1454,18 @@ vmmci_ctl(unsigned int cmd)
 		tv.tv_sec = VMMCI_TIMEOUT;
 		evtimer_add(&vmmci.timeout, &tv);
 		break;
+	case VMMCI_SYNCRTC:
+		if (vmmci.cfg.guest_feature & VMMCI_F_SYNCRTC) {
+			/* RTC updated, request guest VM resync of its RTC */
+			vmmci.cmd = cmd;
+
+			vmmci.cfg.isr_status = VIRTIO_CONFIG_ISR_CONFIG_CHANGE;
+			vcpu_assert_pic_irq(vmmci.vm_id, 0, vmmci.irq);
+		} else {
+			log_debug("%s: RTC sync skipped (guest does not "
+			    "support RTC sync)\n", __func__);
+		}
+		break;
 	default:
 		fatalx("invalid vmmci command: %d", cmd);
 	}
@@ -1499,6 +1512,11 @@ vmmci_ack(unsigned int cmd)
 			evtimer_add(&vmmci.timeout, &tv);
 		}
 		break;
+	case VMMCI_SYNCRTC:
+		log_debug("%s: vm %u acknowledged RTC sync request",
+		    __func__, vmmci.vm_id);
+		vmmci.cmd = VMMCI_NONE;
+		break;
 	default:
 		log_warnx("%s: illegal request %u", __func__, cmd);
 		break;
@@ -1774,7 +1792,8 @@ virtio_init(struct vmd_vm *vm, int *child_disks, int *child_taps)
 	}
 
 	memset(&vmmci, 0, sizeof(vmmci));
-	vmmci.cfg.device_feature = VMMCI_F_TIMESYNC|VMMCI_F_ACK;
+	vmmci.cfg.device_feature = VMMCI_F_TIMESYNC | VMMCI_F_ACK |
+	    VMMCI_F_SYNCRTC;
 	vmmci.vm_id = vcp->vcp_id;
 	vmmci.irq = pci_get_dev_irq(id);
 
diff --git a/usr.sbin/vmd/virtio.h b/usr.sbin/vmd/virtio.h
index a830d1738d0..05559fc7342 100644
--- a/usr.sbin/vmd/virtio.h
+++ b/usr.sbin/vmd/virtio.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: virtio.h,v 1.15 2017/04/19 15:38:32 reyk Exp $	*/
+/*	$OpenBSD: virtio.h,v 1.16 2017/05/02 09:51:19 mlarkin Exp $	*/
 
 /*
  * Copyright (c) 2015 Mike Larkin <mlarkin@openbsd.org>
@@ -147,6 +147,7 @@ enum vmmci_cmd {
 	VMMCI_NONE = 0,
 	VMMCI_SHUTDOWN,
 	VMMCI_REBOOT,
+	VMMCI_SYNCRTC,
 };
 
 struct vmmci_dev {
-- 
2.20.1