bhyve: namescope virtio_msix to virtio.msix

The bhyve_config(5) variable `virtio_msix` is namescoped to
`virtio.msix`. Configurations that have the old variable will
automatically be mapped to the new one, with a warning message printed
out.

Relnotes:	yes
Reviewed by:	ziaee, markj
Differential Revision:	https://reviews.freebsd.org/D58390

usr.sbin/bhyve/aarch64/bhyverun_machdep.c

@@ -183,7 +183,7 @@ bhyve_optparse(int argc, char **argv)
 			set_config_value("uuid", optarg);
 			break;
 		case 'W':
-			set_config_bool("virtio_msix", false);
+			set_config_bool("virtio.msix", false);
 			break;
 		case 'h':
 			bhyve_usage(0);
@@ -191,6 +191,9 @@ bhyve_optparse(int argc, char **argv)
 			bhyve_usage(1);
 		}
 	}
+
+	/* Handle backwards compatibility aliases in config options. */
+	bhyve_cfg_warn("virtio_msix", "virtio.msix");
 }
 
 void

usr.sbin/bhyve/amd64/bhyverun_machdep.c

@@ -250,7 +250,7 @@ bhyve_optparse(int argc, char **argv)
 			set_config_bool("x86.strictmsr", false);
 			break;
 		case 'W':
-			set_config_bool("virtio_msix", false);
+			set_config_bool("virtio.msix", false);
 			break;
 		case 'x':
 			set_config_bool("x86.x2apic", true);
@@ -268,6 +268,7 @@ bhyve_optparse(int argc, char **argv)
 	/* Handle backwards compatibility aliases in config options. */
 	bhyve_cfg_warn("lpc.bootrom", "bootrom");
 	bhyve_cfg_warn("lpc.bootvars", "bootvars");
+	bhyve_cfg_warn("virtio_msix", "virtio.msix");
 }
 
 void

usr.sbin/bhyve/bhyve_config.5

@@ -24,7 +24,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd July 8, 2026
+.Dd August 10, 2026
 .Dt BHYVE_CONFIG 5
 .Os
 .Sh NAME
@@ -169,7 +169,7 @@ The universally unique identifier (UUID) to use in the guest's
 System Management BIOS System Information structure.
 If an explicit value is not set, a valid UUID is generated from
 the host's hostname and the VM name.
-.It Va virtio_msix Ta bool Ta true Ta
+.It Va virtio.msix Ta bool Ta true Ta
 Use MSI-X interrupts for PCI VirtIO devices.
 If set to false, MSI interrupts are used instead.
 .It Va config.dump Ta bool Ta false Ta

usr.sbin/bhyve/riscv/bhyverun_machdep.c

@@ -174,7 +174,7 @@ bhyve_optparse(int argc, char **argv)
 			set_config_value("uuid", optarg);
 			break;
 		case 'W':
-			set_config_bool("virtio_msix", false);
+			set_config_bool("virtio.msix", false);
 			break;
 		case 'h':
 			bhyve_usage(0);
@@ -182,6 +182,9 @@ bhyve_optparse(int argc, char **argv)
 			bhyve_usage(1);
 		}
 	}
+
+	/* Handle backwards compatibility aliases in config options. */
+	bhyve_cfg_warn("virtio_msix", "virtio.msix");
 }
 
 void