[Xen-devel] [PATCH 1/2] mini-os: support keeping start_info structure conditionally

[Juergen Gross <jgross@xxxxxxxx>]

grub stubdom needs the start_info structure. Keep a copy of it in
pv mini-os if configured via "CONFIG_KEEP_STARTINFO". This should
default to "n" in order to have it enabled only when really needed.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 Config.mk            |  2 ++
 arch/x86/setup.c     | 12 ++++++++++++
 include/hypervisor.h | 13 +++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/Config.mk b/Config.mk
index aa36761..ae18ffd 100644
--- a/Config.mk
+++ b/Config.mk
@@ -175,6 +175,7 @@ CONFIG_XENBUS ?= y
 CONFIG_XC ?=y
 CONFIG_LWIP ?= $(lwip)
 CONFIG_BALLOON ?= n
+CONFIG_KEEP_STARTINFO ?= n
 
 # Export config items as compiler directives
 DEFINES-$(CONFIG_PARAVIRT) += -DCONFIG_PARAVIRT
@@ -192,6 +193,7 @@ DEFINES-$(CONFIG_FBFRONT) += -DCONFIG_FBFRONT
 DEFINES-$(CONFIG_CONSFRONT) += -DCONFIG_CONSFRONT
 DEFINES-$(CONFIG_XENBUS) += -DCONFIG_XENBUS
 DEFINES-$(CONFIG_BALLOON) += -DCONFIG_BALLOON
+DEFINES-$(CONFIG_KEEP_STARTINFO) += -DCONFIG_KEEP_STARTINFO
 
 # Override settings for this OS
 PTHREAD_LIBS =
diff --git a/arch/x86/setup.c b/arch/x86/setup.c
index 86955cf..1761b81 100644
--- a/arch/x86/setup.c
+++ b/arch/x86/setup.c
@@ -33,6 +33,14 @@
 #include <xen/arch-x86/cpuid.h>
 #include <xen/arch-x86/hvm/start_info.h>
 
+#ifdef CONFIG_KEEP_STARTINFO
+/*
+ * This structure contains start-of-day info, such as pagetable base pointer,
+ * address of the shared_info structure, and things like that.
+ */
+union start_info_union start_info_union;
+#endif
+
 /*
  * Shared page for communicating with the hypervisor.
  * Events flags go here, for example.
@@ -189,6 +197,10 @@ arch_init(void *par)
        /* print out some useful information  */
        print_start_of_day(par);
 
+#ifdef CONFIG_KEEP_STARTINFO
+       memcpy(&start_info, par, sizeof(start_info));
+#endif
+
        start_kernel();
 }
 
diff --git a/include/hypervisor.h b/include/hypervisor.h
index 3073a8a..5475867 100644
--- a/include/hypervisor.h
+++ b/include/hypervisor.h
@@ -27,6 +27,19 @@
 #include <mini-os/traps.h>
 
 /* hypervisor.c */
+#ifdef CONFIG_KEEP_STARTINFO
+/*
+ * a placeholder for the start of day information passed up from the hypervisor
+ */
+union start_info_union
+{
+    start_info_t start_info;
+    char padding[512];
+};
+extern union start_info_union start_info_union;
+#define start_info (start_info_union.start_info)
+#endif
+
 #ifndef CONFIG_PARAVIRT
 int hvm_get_parameter(int idx, uint64_t *value);
 int hvm_set_parameter(int idx, uint64_t value);
-- 
2.6.6


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