[PATCH v2 RESEND 1/2] x86/UV: Introduce a helper function to check UV system at earlier stage

[Baoquan He <bhe@redhat.com>]

The BIOS on SGI UV system will report a UV system table which describes
specific firmware capabilities available to the Linux kernel at runtime.
This UV system table only exists on SGI UV system. And it's detected
in efi_init() which is at very early stage.

So introduce a new helper function is_early_uv_system() to identify if
a system is UV system. Later we will use it to check if the running
system is UV system in mm KASLR code.

Signed-off-by: Baoquan He <bhe@redhat.com>
Acked-by: Mike Travis <travis@sgi.com>
---
 arch/x86/include/asm/uv/uv.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/include/asm/uv/uv.h b/arch/x86/include/asm/uv/uv.h
index b5a32231abd8..93d7ad8763ba 100644
--- a/arch/x86/include/asm/uv/uv.h
+++ b/arch/x86/include/asm/uv/uv.h
@@ -18,6 +18,11 @@ extern void uv_nmi_init(void);
 extern void uv_system_init(void);
 extern const struct cpumask *uv_flush_tlb_others(const struct cpumask *cpumask,
 						 const struct flush_tlb_info *info);
+#include <linux/efi.h>
+static inline int is_early_uv_system(void)
+{
+	return !((efi.uv_systab == EFI_INVALID_TABLE_ADDR) || !efi.uv_systab);
+}
 
 #else	/* X86_UV */
 
@@ -30,6 +35,7 @@ static inline const struct cpumask *
 uv_flush_tlb_others(const struct cpumask *cpumask,
 		    const struct flush_tlb_info *info)
 { return cpumask; }
+static inline int is_early_uv_system(void)	{ return 0; }
 
 #endif	/* X86_UV */
 
-- 
2.5.5