[Xen-devel] [RFC 2/9] x86: Introduce Xen detection as separate logic from Xen Guest support.

[Christopher Clark <christopher.w.clark@gmail.com>]

Add Kconfig option XEN_DETECT for:
  "Support for Xen detecting when it is running under Xen".
If running under Xen is detected, a boot message will indicate the
hypervisor version obtained from cpuid.

Update the XEN_GUEST Kconfig option text to reflect its current
purpose:
  "Common PVH_GUEST and PV_SHIM logic for Xen as a Xen-aware guest".

Update calibrate_APIC_clock to use Xen-specific init if nested Xen is
detected, even if not operating as a PV shim or booted as PVH.

This work is a precursor to adding the interface for support of
PV drivers on nested Xen.

Signed-off-by: Christopher Clark <christopher.clark@starlab.io>
---
 xen/arch/x86/Kconfig            | 11 ++++++++++-
 xen/arch/x86/Makefile           |  2 +-
 xen/arch/x86/apic.c             |  4 ++--
 xen/arch/x86/guest/Makefile     |  2 +-
 xen/arch/x86/guest/xen-guest.c  | 10 ++++++++++
 xen/arch/x86/guest/xen.c        | 23 ++++++++++++++++++-----
 xen/arch/x86/setup.c            |  3 +++
 xen/include/asm-x86/guest/xen.h | 26 +++++++++++++++++++++-----
 8 files changed, 66 insertions(+), 15 deletions(-)

diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index f502d765ba..31e5ffd2f2 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -161,11 +161,20 @@ config XEN_ALIGN_2M
 
 endchoice
 
+config XEN_DETECT
+	def_bool y
+	prompt "Xen Detection"
+	---help---
+	  Support for Xen detecting when it is running under Xen.
+
+	  If unsure, say Y.
+
 config XEN_GUEST
 	def_bool n
 	prompt "Xen Guest"
+	depends on XEN_DETECT
 	---help---
-	  Support for Xen detecting when it is running under Xen.
+	  Common PVH_GUEST and PV_SHIM logic for Xen as a Xen-aware guest.
 
 	  If unsure, say N.
 
diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 8a8d8f060f..763077b0a3 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -1,7 +1,7 @@
 subdir-y += acpi
 subdir-y += cpu
 subdir-y += genapic
-subdir-$(CONFIG_XEN_GUEST) += guest
+subdir-$(CONFIG_XEN_DETECT) += guest
 subdir-$(CONFIG_HVM) += hvm
 subdir-y += mm
 subdir-$(CONFIG_XENOPROF) += oprofile
diff --git a/xen/arch/x86/apic.c b/xen/arch/x86/apic.c
index 9c3c998d34..5949a95d58 100644
--- a/xen/arch/x86/apic.c
+++ b/xen/arch/x86/apic.c
@@ -1247,7 +1247,7 @@ static int __init calibrate_APIC_clock(void)
      */
     __setup_APIC_LVTT(1000000000);
 
-    if ( !xen_guest )
+    if ( !xen_detected )
         /*
          * The timer chip counts down to zero. Let's wait
          * for a wraparound to start exact measurement:
@@ -1267,7 +1267,7 @@ static int __init calibrate_APIC_clock(void)
      * Let's wait LOOPS ticks:
      */
     for (i = 0; i < LOOPS; i++)
-        if ( !xen_guest )
+        if ( !xen_detected )
             wait_8254_wraparound();
         else
             wait_tick_pvh();
diff --git a/xen/arch/x86/guest/Makefile b/xen/arch/x86/guest/Makefile
index 6ddaa3748f..d3a7844e61 100644
--- a/xen/arch/x86/guest/Makefile
+++ b/xen/arch/x86/guest/Makefile
@@ -1,4 +1,4 @@
-obj-y += hypercall_page.o
+obj-$(CONFIG_XEN_GUEST) += hypercall_page.o
 obj-y += xen.o
 obj-$(CONFIG_XEN_GUEST) += xen-guest.o
 
diff --git a/xen/arch/x86/guest/xen-guest.c b/xen/arch/x86/guest/xen-guest.c
index 65596ab1b1..b6d89e02a3 100644
--- a/xen/arch/x86/guest/xen-guest.c
+++ b/xen/arch/x86/guest/xen-guest.c
@@ -35,6 +35,8 @@
 #include <public/arch-x86/cpuid.h>
 #include <public/hvm/params.h>
 
+extern char hypercall_page[];
+
 bool __read_mostly xen_guest;
 
 static struct rangeset *mem;
@@ -45,6 +47,14 @@ static struct vcpu_info *vcpu_info;
 static unsigned long vcpu_info_mapped[BITS_TO_LONGS(NR_CPUS)];
 DEFINE_PER_CPU(struct vcpu_info *, vcpu_info);
 
+void xen_guest_enable(void)
+{
+    /* Fill the hypercall page. */
+    wrmsrl(cpuid_ebx(hypervisor_cpuid_base() + 2), __pa(hypercall_page));
+
+    xen_guest = true;
+}
+
 static void map_shared_info(void)
 {
     mfn_t mfn;
diff --git a/xen/arch/x86/guest/xen.c b/xen/arch/x86/guest/xen.c
index 90d464bdbd..b0b603a11a 100644
--- a/xen/arch/x86/guest/xen.c
+++ b/xen/arch/x86/guest/xen.c
@@ -33,8 +33,10 @@
 #include <public/arch-x86/cpuid.h>
 #include <public/hvm/params.h>
 
+/* xen_detected: Xen running on Xen detected */
+bool __read_mostly xen_detected;
+
 static __read_mostly uint32_t xen_cpuid_base;
-extern char hypercall_page[];
 
 static void __init find_xen_leaves(void)
 {
@@ -58,7 +60,7 @@ static void __init find_xen_leaves(void)
 
 void __init probe_hypervisor(void)
 {
-    if ( xen_guest )
+    if ( xen_detected )
         return;
 
     /* Too early to use cpu_has_hypervisor */
@@ -70,10 +72,21 @@ void __init probe_hypervisor(void)
     if ( !xen_cpuid_base )
         return;
 
-    /* Fill the hypercall page. */
-    wrmsrl(cpuid_ebx(xen_cpuid_base + 2), __pa(hypercall_page));
+    xen_detected = true;
+
+    xen_guest_enable();
+}
+
+void __init hypervisor_print_info(void)
+{
+    uint32_t eax, ebx, ecx, edx;
+    unsigned int major, minor;
+
+    cpuid(xen_cpuid_base + 1, &eax, &ebx, &ecx, &edx);
 
-    xen_guest = true;
+    major = eax >> 16;
+    minor = eax & 0xffff;
+    printk("Nested Xen version %u.%u.\n", major, minor);
 }
 
 uint32_t hypervisor_cpuid_base(void)
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index d2011910fa..58f499edaf 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -774,6 +774,9 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     ehci_dbgp_init();
     console_init_preirq();
 
+    if ( xen_detected )
+        hypervisor_print_info();
+
     if ( pvh_boot )
         pvh_print_info();
 
diff --git a/xen/include/asm-x86/guest/xen.h b/xen/include/asm-x86/guest/xen.h
index 7e04e4a7ab..27c854ab8a 100644
--- a/xen/include/asm-x86/guest/xen.h
+++ b/xen/include/asm-x86/guest/xen.h
@@ -24,20 +24,37 @@
 #include <asm/e820.h>
 #include <asm/fixmap.h>
 
-#define XEN_shared_info ((struct shared_info *)fix_to_virt(FIX_XEN_SHARED_INFO))
+#ifdef CONFIG_XEN_DETECT
+
+extern bool xen_detected;
+
+void probe_hypervisor(void);
+void hypervisor_print_info(void);
+uint32_t hypervisor_cpuid_base(void);
+
+#else
+
+#define xen_detected 0
+
+static inline void probe_hypervisor(void) {}
+static inline void hypervisor_print_info(void) {
+    ASSERT_UNREACHABLE();
+}
+
+#endif /* CONFIG_XEN_DETECT */
 
 #ifdef CONFIG_XEN_GUEST
+#define XEN_shared_info ((struct shared_info *)fix_to_virt(FIX_XEN_SHARED_INFO))
 
 extern bool xen_guest;
 extern bool pv_console;
 
-void probe_hypervisor(void);
 void hypervisor_setup(void);
 void hypervisor_ap_setup(void);
 int hypervisor_alloc_unused_page(mfn_t *mfn);
 int hypervisor_free_unused_page(mfn_t mfn);
-uint32_t hypervisor_cpuid_base(void);
 void hypervisor_resume(void);
+void xen_guest_enable(void);
 
 DECLARE_PER_CPU(unsigned int, vcpu_id);
 DECLARE_PER_CPU(struct vcpu_info *, vcpu_info);
@@ -47,8 +64,6 @@ DECLARE_PER_CPU(struct vcpu_info *, vcpu_info);
 #define xen_guest 0
 #define pv_console 0
 
-static inline void probe_hypervisor(void) {}
-
 static inline void hypervisor_setup(void)
 {
     ASSERT_UNREACHABLE();
@@ -57,6 +72,7 @@ static inline void hypervisor_ap_setup(void)
 {
     ASSERT_UNREACHABLE();
 }
+static inline void xen_guest_enable(void) {}
 
 #endif /* CONFIG_XEN_GUEST */
 #endif /* __X86_GUEST_XEN_H__ */
-- 
2.17.1


_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel