x86/entry: Probe for Xen early during boot

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
v2: Add __read_mostly.

5 files changed, 127 insertions, 0 deletions

diff --git a/xen/arch/x86/guest/Makefile b/xen/arch/x86/guest/Makefile
index a5f1625ab1..1345a60c81 100644
--- a/xen/arch/x86/guest/Makefile
+++ b/xen/arch/x86/guest/Makefile
@@ -1 +1,3 @@
+obj-y += xen.o
+
 obj-bin-$(CONFIG_PVH_GUEST) += pvh-boot.init.o
diff --git a/xen/arch/x86/guest/xen.c b/xen/arch/x86/guest/xen.c
new file mode 100644
index 0000000000..8507757841
--- /dev/null
+++ b/xen/arch/x86/guest/xen.c
@@ -0,0 +1,75 @@
+/******************************************************************************
+ * arch/x86/guest/xen.c
+ *
+ * Support for detecting and running under Xen.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright (c) 2017 Citrix Systems Ltd.
+ */
+#include <xen/init.h>
+#include <xen/types.h>
+
+#include <asm/guest.h>
+#include <asm/processor.h>
+
+#include <public/arch-x86/cpuid.h>
+
+bool __read_mostly xen_guest;
+
+static __read_mostly uint32_t xen_cpuid_base;
+
+static void __init find_xen_leaves(void)
+{
+    uint32_t eax, ebx, ecx, edx, base;
+
+    for ( base = XEN_CPUID_FIRST_LEAF;
+          base < XEN_CPUID_FIRST_LEAF + 0x10000; base += 0x100 )
+    {
+        cpuid(base, &eax, &ebx, &ecx, &edx);
+
+        if ( (ebx == XEN_CPUID_SIGNATURE_EBX) &&
+             (ecx == XEN_CPUID_SIGNATURE_ECX) &&
+             (edx == XEN_CPUID_SIGNATURE_EDX) &&
+             ((eax - base) >= 2) )
+        {
+            xen_cpuid_base = base;
+            break;
+        }
+    }
+}
+
+void __init probe_hypervisor(void)
+{
+    /* Too early to use cpu_has_hypervisor */
+    if ( !(cpuid_ecx(1) & cpufeat_mask(X86_FEATURE_HYPERVISOR)) )
+        return;
+
+    find_xen_leaves();
+
+    if ( !xen_cpuid_base )
+        return;
+
+    xen_guest = true;
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 4b8d09b751..d8059f23b5 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -715,6 +715,8 @@ void __init noreturn __start_xen(unsigned long mbi_p)
      * allocing any xenheap structures wanted in lower memory. */
     kexec_early_calculations();
 
+    probe_hypervisor();
+
     parse_video_info();
 
     rdmsrl(MSR_EFER, this_cpu(efer));
diff --git a/xen/include/asm-x86/guest.h b/xen/include/asm-x86/guest.h
index 630c092c25..8d91f81451 100644
--- a/xen/include/asm-x86/guest.h
+++ b/xen/include/asm-x86/guest.h
@@ -20,6 +20,7 @@
 #define __X86_GUEST_H__
 
 #include <asm/guest/pvh-boot.h>
+#include <asm/guest/xen.h>
 
 #endif /* __X86_GUEST_H__ */
 
diff --git a/xen/include/asm-x86/guest/xen.h b/xen/include/asm-x86/guest/xen.h
new file mode 100644
index 0000000000..97a7c8d531
--- /dev/null
+++ b/xen/include/asm-x86/guest/xen.h
@@ -0,0 +1,47 @@
+/******************************************************************************
+ * asm-x86/guest/xen.h
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms and conditions of the GNU General Public
+ * License, version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright (c) 2017 Citrix Systems Ltd.
+ */
+
+#ifndef __X86_GUEST_XEN_H__
+#define __X86_GUEST_XEN_H__
+
+#include <xen/types.h>
+
+#ifdef CONFIG_XEN_GUEST
+
+extern bool xen_guest;
+
+void probe_hypervisor(void);
+
+#else
+
+#define xen_guest 0
+
+static inline void probe_hypervisor(void) {};
+
+#endif /* CONFIG_XEN_GUEST */
+#endif /* __X86_GUEST_XEN_H__ */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */