linux-kernel - [PATCH 3.2 032/104] x86, cpu: Expand cpufeature facility to include cpu bugs

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Message-ID: <lsq.1520823814.933529292@decadent.org.uk>
Date:   Mon, 12 Mar 2018 03:03:34 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Borislav Petkov" <bp@...e.de>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH 3.2 032/104] x86, cpu: Expand cpufeature facility to
 include cpu bugs

3.2.101-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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

commit 65fc985b37dc241c4db7cd32adcbc989193fe3c8 upstream.

We add another 32-bit vector at the end of the ->x86_capability
bitvector which collects bugs present in CPUs. After all, a CPU bug is a
kind of a capability, albeit a strange one.

Signed-off-by: Borislav Petkov <bp@...e.de>
Link: http://lkml.kernel.org/r/1363788448-31325-2-git-send-email-bp@alien8.de
Signed-off-by: H. Peter Anvin <hpa@...or.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/include/asm/cpufeature.h | 13 +++++++++++++
 arch/x86/include/asm/processor.h  |  2 +-
 arch/x86/kernel/alternative.c     |  2 +-
 arch/x86/kernel/cpu/common.c      |  4 ++++
 4 files changed, 19 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -7,6 +7,7 @@
 #include <asm/required-features.h>
 
 #define NCAPINTS	10	/* N 32-bit words worth of info */
+#define NBUGINTS	1	/* N 32-bit bug flags */
 
 /*
  * Note: If the comment begins with a quoted string, that string is used
@@ -208,6 +209,11 @@
 #define X86_FEATURE_INVPCID	(9*32+10) /* Invalidate Processor Context ID */
 #define X86_FEATURE_RTM		(9*32+11) /* Restricted Transactional Memory */
 
+/*
+ * BUG word(s)
+ */
+#define X86_BUG(x)		(NCAPINTS*32 + (x))
+
 #if defined(__KERNEL__) && !defined(__ASSEMBLY__)
 
 #include <asm/asm.h>
@@ -397,6 +403,13 @@ static __always_inline __pure bool __sta
 #define static_cpu_has(bit) boot_cpu_has(bit)
 #endif
 
+#define cpu_has_bug(c, bit)	cpu_has(c, (bit))
+#define set_cpu_bug(c, bit)	set_cpu_cap(c, (bit))
+#define clear_cpu_bug(c, bit)	clear_cpu_cap(c, (bit));
+
+#define static_cpu_has_bug(bit)	static_cpu_has((bit))
+#define boot_cpu_has_bug(bit)	cpu_has_bug(&boot_cpu_data, (bit))
+
 #endif /* defined(__KERNEL__) && !defined(__ASSEMBLY__) */
 
 #endif /* _ASM_X86_CPUFEATURE_H */
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -86,7 +86,7 @@ struct cpuinfo_x86 {
 	__u32			extended_cpuid_level;
 	/* Maximum supported CPUID level, -1=no CPUID: */
 	int			cpuid_level;
-	__u32			x86_capability[NCAPINTS];
+	__u32			x86_capability[NCAPINTS + NBUGINTS];
 	char			x86_vendor_id[16];
 	char			x86_model_id[64];
 	/* in KB - valid for CPUS which support this call: */
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -359,7 +359,7 @@ void __init_or_module apply_alternatives
 		instr = (u8 *)&a->instr_offset + a->instr_offset;
 		replacement = (u8 *)&a->repl_offset + a->repl_offset;
 		BUG_ON(a->instrlen > sizeof(insnbuf));
-		BUG_ON(a->cpuid >= NCAPINTS*32);
+		BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32);
 		if (!boot_cpu_has(a->cpuid)) {
 			if (a->padlen > 1)
 				optimize_nops(a, instr);
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -954,6 +954,10 @@ static void __cpuinit identify_cpu(struc
 		/* AND the already accumulated flags with these */
 		for (i = 0; i < NCAPINTS; i++)
 			boot_cpu_data.x86_capability[i] &= c->x86_capability[i];
+
+		/* OR, i.e. replicate the bug flags */
+		for (i = NCAPINTS; i < NCAPINTS + NBUGINTS; i++)
+			c->x86_capability[i] |= boot_cpu_data.x86_capability[i];
 	}
 
 	/* Init Machine Check Exception if available. */