From 8ccb28efcdc2351e5ebed1aea228f10850032ef2 Mon Sep 17 00:00:00 2001
From: Neel Natu <neel@FreeBSD.org>
Date: Tue, 7 Oct 2014 17:08:53 +0000
Subject: [PATCH] Implement the FLUSH operation in the virtio-block emulation.

This gets rid of the following error message during FreeBSD guest bootup:
"vtbd0: hard error cmd=flush fsbn 0"

Reported by:	rodrigc
Reviewed by:	grehan
---
 usr.sbin/bhyve/pci_virtio_block.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/usr.sbin/bhyve/pci_virtio_block.c b/usr.sbin/bhyve/pci_virtio_block.c
index 394b116b3028..c66ad68936bc 100644
--- a/usr.sbin/bhyve/pci_virtio_block.c
+++ b/usr.sbin/bhyve/pci_virtio_block.c
@@ -94,6 +94,8 @@ struct vtblk_config {
 struct virtio_blk_hdr {
 #define	VBH_OP_READ		0
 #define	VBH_OP_WRITE		1
+#define	VBH_OP_FLUSH		4
+#define	VBH_OP_FLUSH_OUT	5
 #define	VBH_OP_IDENT		8		
 #define	VBH_FLAG_BARRIER	0x80000000	/* OR'ed into vbh_type */
 	uint32_t       	vbh_type;
@@ -217,6 +219,10 @@ pci_vtblk_proc(struct pci_vtblk_softc *sc, struct vqueue_info *vq)
 		    MIN(iov[1].iov_len, sizeof(sc->vbsc_ident)));
 		err = 0;
 		break;
+	case VBH_OP_FLUSH:
+	case VBH_OP_FLUSH_OUT:
+		err = fsync(sc->vbsc_fd);
+		break;
 	default:
 		err = -ENOSYS;
 		break;