linux-kernel - [PATCH] x86/fixmap: Set the debugstore fixmap entries on Intel only

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Date:   Fri, 15 Dec 2017 13:47:26 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     X86 ML <x86@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirsky <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Greg KH <gregkh@...uxfoundation.org>, keescook@...gle.com,
        hughd@...gle.com, Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        David Laight <David.Laight@...lab.com>,
        Eduardo Valentin <eduval@...zon.com>, aliguori@...zon.com,
        Will Deacon <will.deacon@....com>, daniel.gruss@...k.tugraz.at
Subject: [PATCH] x86/fixmap: Set the debugstore fixmap entries on Intel only

From: Borislav Petkov <bp@...e.de>

No need to setup those during boot on !Intel vendors.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andy Lutomirsky <luto@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Greg KH <gregkh@...uxfoundation.org>
Cc: keescook@...gle.com
Cc: hughd@...gle.com
Cc: Brian Gerst <brgerst@...il.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: David Laight <David.Laight@...lab.com>
Cc: Eduardo Valentin <eduval@...zon.com>
Cc: aliguori@...zon.com
Cc: Will Deacon <will.deacon@....com>
Cc: daniel.gruss@...k.tugraz.at
---
 arch/x86/kernel/cpu/common.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 7b2988e521a7..bca5570d40bc 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -582,12 +582,16 @@ static void __init setup_cpu_entry_area(int cpu)
 
 #ifdef CONFIG_CPU_SUP_INTEL
 	BUILD_BUG_ON(sizeof(struct debug_store) % PAGE_SIZE != 0);
-	set_percpu_fixmap_pages(get_cpu_entry_area_index(cpu, cpu_debug_store),
-				&per_cpu(cpu_debug_store, cpu),
-				sizeof(struct debug_store) / PAGE_SIZE,
-				PAGE_KERNEL);
-	set_percpu_fixmap_ptes(get_cpu_entry_area_index(cpu, cpu_debug_buffers),
-			       sizeof(struct debug_store_buffers) / PAGE_SIZE);
+
+	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
+		set_percpu_fixmap_pages(get_cpu_entry_area_index(cpu, cpu_debug_store),
+					&per_cpu(cpu_debug_store, cpu),
+					sizeof(struct debug_store) / PAGE_SIZE,
+					PAGE_KERNEL);
+
+		set_percpu_fixmap_ptes(get_cpu_entry_area_index(cpu, cpu_debug_buffers),
+				       sizeof(struct debug_store_buffers) / PAGE_SIZE);
+	}
 #endif
 	set_percpu_fixmap_ptes(get_cpu_entry_area_index(cpu, ldt_entries),
 			       (LDT_ENTRIES * LDT_ENTRY_SIZE) / PAGE_SIZE);
-- 
2.13.0