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From:   Pavel Tatashin <pasha.tatashin@oracle.com>
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Subject: [PATCH 4.1 18/65] x86/mm: Disable PCID on 32-bit kernels
Date:   Mon,  5 Mar 2018 19:24:51 -0500
Message-Id: <20180306002538.1761-19-pasha.tatashin@oracle.com>
In-Reply-To: <20180306002538.1761-1-pasha.tatashin@oracle.com>
References: <20180306002538.1761-1-pasha.tatashin@oracle.com>
Sender: linux-kernel-owner@vger.kernel.org
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From: Andy Lutomirski <luto@kernel.org>

commit cba4671af7550e008f7a7835f06df0763825bf3e upstream.

32-bit kernels on new hardware will see PCID in CPUID, but PCID can
only be used in 64-bit mode.  Rather than making all PCID code
conditional, just disable the feature on 32-bit builds.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Nadav Amit <nadav.amit@gmail.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/2e391769192a4d31b808410c383c6bf0734bc6ea.1498751203.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

(cherry picked from commit 78043e5b6fb2921d836b31f23e89e52925191153)
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
---
 arch/x86/include/asm/disabled-features.h | 4 +++-
 arch/x86/kernel/cpu/bugs.c               | 8 ++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index f226df064660..8b17c2ad1048 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -21,11 +21,13 @@
 # define DISABLE_K6_MTRR	(1<<(X86_FEATURE_K6_MTRR & 31))
 # define DISABLE_CYRIX_ARR	(1<<(X86_FEATURE_CYRIX_ARR & 31))
 # define DISABLE_CENTAUR_MCR	(1<<(X86_FEATURE_CENTAUR_MCR & 31))
+# define DISABLE_PCID		0
 #else
 # define DISABLE_VME		0
 # define DISABLE_K6_MTRR	0
 # define DISABLE_CYRIX_ARR	0
 # define DISABLE_CENTAUR_MCR	0
+# define DISABLE_PCID		(1<<(X86_FEATURE_PCID & 31))
 #endif /* CONFIG_X86_64 */
 
 /*
@@ -35,7 +37,7 @@
 #define DISABLED_MASK1	0
 #define DISABLED_MASK2	0
 #define DISABLED_MASK3	(DISABLE_CYRIX_ARR|DISABLE_CENTAUR_MCR|DISABLE_K6_MTRR)
-#define DISABLED_MASK4	0
+#define DISABLED_MASK4	(DISABLE_PCID)
 #define DISABLED_MASK5	0
 #define DISABLED_MASK6	0
 #define DISABLED_MASK7	0
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 03445346ee0a..4c7dd836304a 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -65,6 +65,14 @@ static void __init check_fpu(void)
 
 void __init check_bugs(void)
 {
+#ifdef CONFIG_X86_32
+	/*
+	 * Regardless of whether PCID is enumerated, the SDM says
+	 * that it can't be enabled in 32-bit mode.
+	 */
+	setup_clear_cpu_cap(X86_FEATURE_PCID);
+#endif
+
 	identify_boot_cpu();
 #ifndef CONFIG_SMP
 	pr_info("CPU: ");
-- 
2.16.2