OvmfPkg: Add BaseResetSystemLibBhyve

Introduce BaseResetSystemLibBhyve.inf, to support powering off
bhyve guests.

Signed-off-by: Rebecca Cran <rebecca@bsdio.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Message-Id: <20200504021853.76658-1-rebecca@bsdio.com>
[lersek@redhat.com: MODULE_TYPE: replace DXE_DRIVER with BASE]
[lersek@redhat.com: replace <OvmfPlatforms.h> with <IndustryStandard/Bhyve.h>]
[lersek@redhat.com: strip ".inf" from subject line]
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

OvmfPkg/Library/ResetSystemLib/BaseResetShutdownBhyve.c

@@ -0,0 +1,34 @@
+/** @file
+  Base Reset System Library Shutdown API implementation for bhyve.
+
+  Copyright (C) 2020, Rebecca Cran <rebecca@bsdio.com>
+  Copyright (C) 2020, Red Hat, Inc.
+  Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#include <Base.h>                   // BIT13
+
+#include <IndustryStandard/Bhyve.h> // BHYVE_PM_REG
+#include <Library/BaseLib.h>        // CpuDeadLoop()
+#include <Library/IoLib.h>          // IoOr16()
+#include <Library/ResetSystemLib.h> // ResetShutdown()
+
+/**
+  Calling this function causes the system to enter a power state equivalent
+  to the ACPI G2/S5 or G3 states.
+
+  System shutdown should not return, if it returns, it means the system does
+  not support shut down reset.
+**/
+VOID
+EFIAPI
+ResetShutdown (
+  VOID
+  )
+{
+  IoBitFieldWrite16 (BHYVE_PM_REG, 10, 13, 5);
+  IoOr16 (BHYVE_PM_REG, BIT13);
+  CpuDeadLoop ();
+}