Add runningOnQEMU() and runningOnXen() for runtime platform detection.

Introduce standard for performing and inspecting the run-time
detection of para-virtualized environments.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

5 files changed, 41 insertions, 7 deletions

diff --git a/src/Kconfig b/src/Kconfig
index bbcefe0..c125e00 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -14,9 +14,10 @@ choice
             Configure as a coreboot payload.
 
     config QEMU
-        bool "Build for QEMU"
+        bool "Build for QEMU/Xen/KVM/Bochs"
+        select QEMU_HARDWARE
         help
-            Configure as QEMU bios.
+            Configure for an emulated machine (QEMU, Xen, KVM, or Bochs).
 
     config CSM
        bool "Build as Compatibilty Support Module for EFI BIOS"
@@ -26,9 +27,16 @@ choice
 
 endchoice
 
+    config QEMU_HARDWARE
+        bool "Support hardware found on emulators (QEMU/Xen/KVM/Bochs)" if !QEMU
+        default n
+        help
+            Support virtual hardware when the code detects it is
+            running on an emulator.
+
     config XEN
         depends on QEMU
-        bool "Build for Xen HVM"
+        bool "Support Xen HVM"
         default y
         help
             Configure to be used by xen hvmloader, for a HVM guest.
diff --git a/src/misc.c b/src/misc.c
index bcc450a..3b2ffc1 100644
--- a/src/misc.c
+++ b/src/misc.c
@@ -16,6 +16,8 @@ u32 RamSize VAR16VISIBLE;
 u64 RamSizeOver4G;
 // Space for bios tables built an run-time.
 char BiosTableSpace[CONFIG_MAX_BIOSTABLE] __aligned(MALLOC_MIN_ALIGN) VAR16VISIBLE;
+// Type of emulator platform.
+int PlatformRunningOn VAR16VISIBLE;
 
 
 /****************************************************************
diff --git a/src/paravirt.c b/src/paravirt.c
index 9022186..6e230ee 100644
--- a/src/paravirt.c
+++ b/src/paravirt.c
@@ -24,6 +24,11 @@ int qemu_cfg_present;
 void
 qemu_ramsize_preinit(void)
 {
+    if (!CONFIG_QEMU)
+        return;
+
+    PlatformRunningOn = PF_QEMU;
+
     // On emulators, get memory size from nvram.
     u32 rs = ((inb_cmos(CMOS_MEM_EXTMEM2_LOW) << 16)
               | (inb_cmos(CMOS_MEM_EXTMEM2_HIGH) << 24));
diff --git a/src/paravirt.h b/src/paravirt.h
index 4f2d5b8..d32ca13 100644
--- a/src/paravirt.h
+++ b/src/paravirt.h
@@ -1,8 +1,24 @@
 #ifndef __PV_H
 #define __PV_H
 
-#include "config.h" // CONFIG_COREBOOT
-#include "util.h"
+#include "config.h" // CONFIG_*
+#include "util.h" // memcpy
+#include "biosvar.h" // GET_GLOBAL
+
+// Types of paravirtualized platforms.
+#define PF_QEMU     (1<<0)
+#define PF_XEN      (1<<1)
+
+// misc.c
+extern int PlatformRunningOn;
+
+static inline int runningOnQEMU(void) {
+    return CONFIG_QEMU || (
+        CONFIG_QEMU_HARDWARE && GET_GLOBAL(PlatformRunningOn) & PF_QEMU);
+}
+static inline int runningOnXen(void) {
+    return CONFIG_XEN && GET_GLOBAL(PlatformRunningOn) & PF_XEN;
+}
 
 /* This CPUID returns the signature 'KVMKVMKVM' in ebx, ecx, and edx.  It
  * should be used to determine that a VM is running under KVM.
diff --git a/src/xen.c b/src/xen.c
index c9759f0..e075af2 100644
--- a/src/xen.c
+++ b/src/xen.c
@@ -6,7 +6,7 @@
 
 #include "config.h"
 #include "xen.h"
-
+#include "paravirt.h" // PlatformRunningOn
 #include "memmap.h" // add_e820
 #include "types.h" // ASM32FLAT
 #include "util.h" // copy_acpi_rsdp
@@ -76,8 +76,11 @@ void xen_preinit(void)
             break;
         }
     }
-    if (!xen_cpuid_base)
+    if (!xen_cpuid_base) {
         dprintf(1, "No Xen hypervisor found.\n");
+        return;
+    }
+    PlatformRunningOn = PF_QEMU|PF_XEN;
 }
 
 static int hypercall_xen_version( int cmd, void *arg)