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

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Date:   Thu,  7 Sep 2017 15:42:29 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     mingo@...hat.com, tglx@...utronix.de, hpa@...or.com,
        thgarnie@...gle.com, keescook@...omium.org,
        akpm@...ux-foundation.org, yamada.masahiro@...ionext.com,
        rja@....com, frank.ramsay@....com, Baoquan He <bhe@...hat.com>
Subject: [PATCH v2 RESEND 1/2] x86/UV: Introduce a helper function to check UV system at earlier stage

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@...hat.com>
Acked-by: Mike Travis <travis@....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