CPU features verification for the new x86 setup code

Verify that the CPU has enough features to run the kernel.  This may
entail enabling features on some CPUs.

By doing this in the setup code we can be guaranteed to still be able to
write to the console through the BIOS.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/i386/boot/cpu.c

+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright (C) 1991, 1992 Linus Torvalds
+ *   Copyright 2007 rPath, Inc. - All Rights Reserved
+ *
+ *   This file is part of the Linux kernel, and is made available under
+ *   the terms of the GNU General Public License version 2.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * arch/i386/boot/cpu.c
+ *
+ * Check for obligatory CPU features and abort if the features are not
+ * present.
+ */
+
+#include "boot.h"
+#include "bitops.h"
+#include <asm/cpufeature.h>
+
+static char *cpu_name(int level)
+{
+	static char buf[6];
+
+	if (level == 64) {
+		return "x86-64";
+	} else {
+		sprintf(buf, "i%d86", level);
+		return buf;
+	}
+}
+
+int validate_cpu(void)
+{
+	u32 *err_flags;
+	int cpu_level, req_level;
+
+	check_cpu(&cpu_level, &req_level, &err_flags);
+
+	if (cpu_level < req_level) {
+		printf("This kernel requires an %s CPU, ",
+		       cpu_name(req_level));
+		printf("but only detected an %s CPU.\n",
+		       cpu_name(cpu_level));
+		return -1;
+	}
+
+	if (err_flags) {
+		int i, j;
+		puts("This kernel requires the following features "
+		     "not present on the CPU:\n");
+
+		for (i = 0; i < NCAPINTS; i++) {
+			u32 e = err_flags[i];
+
+			for (j = 0; j < 32; j++) {
+				if (e & 1)
+					printf("%d:%d ", i, j);
+
+				e >>= 1;
+			}
+		}
+		putchar('\n');
+		return -1;
+	} else {
+		return 0;
+	}
+}

arch/i386/boot/cpucheck.c

+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright (C) 1991, 1992 Linus Torvalds
+ *   Copyright 2007 rPath, Inc. - All Rights Reserved
+ *
+ *   This file is part of the Linux kernel, and is made available under
+ *   the terms of the GNU General Public License version 2.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * arch/i386/boot/cpucheck.c
+ *
+ * Check for obligatory CPU features and abort if the features are not
+ * present.  This code should be compilable as 16-, 32- or 64-bit
+ * code, so be very careful with types and inline assembly.
+ *
+ * This code should not contain any messages; that requires an
+ * additional wrapper.
+ *
+ * As written, this code is not safe for inclusion into the kernel
+ * proper (after FPU initialization, in particular).
+ */
+
+#ifdef _SETUP
+# include "boot.h"
+# include "bitops.h"
+#endif
+#include <linux/types.h>
+#include <asm/cpufeature.h>
+#include <asm/processor-flags.h>
+#include <asm/required-features.h>
+#include <asm/msr-index.h>
+
+struct cpu_features {
+	int level;		/* Family, or 64 for x86-64 */
+	int model;
+	u32 flags[NCAPINTS];
+};
+
+static struct cpu_features cpu;
+static u32 cpu_vendor[3];
+static u32 err_flags[NCAPINTS];
+
+#ifdef CONFIG_X86_64
+static const int req_level = 64;
+#elif defined(CONFIG_X86_MINIMUM_CPU_FAMILY)
+static const int req_level = CONFIG_X86_MINIMUM_CPU_FAMILY;
+#else
+static const int req_level = 3;
+#endif
+
+static const u32 req_flags[NCAPINTS] =
+{
+	REQUIRED_MASK0,
+	REQUIRED_MASK1,
+	REQUIRED_MASK2,
+	REQUIRED_MASK3,
+	REQUIRED_MASK4,
+	REQUIRED_MASK5,
+	REQUIRED_MASK6,
+	REQUIRED_MASK7,
+};
+
+#define A32(a,b,c,d) (((d) << 24)+((c) << 16)+((b) << 8)+(a))
+
+static int is_amd(void)
+{
+	return cpu_vendor[0] == A32('A','u','t','h') &&
+	       cpu_vendor[1] == A32('e','n','t','i') &&
+	       cpu_vendor[2] == A32('c','A','M','D');
+}
+
+static int is_centaur(void)
+{
+	return cpu_vendor[0] == A32('C','e','n','t') &&
+	       cpu_vendor[1] == A32('a','u','r','H') &&
+	       cpu_vendor[2] == A32('a','u','l','s');
+}
+
+static int is_transmeta(void)
+{
+	return cpu_vendor[0] == A32('G','e','n','u') &&
+	       cpu_vendor[1] == A32('i','n','e','T') &&
+	       cpu_vendor[2] == A32('M','x','8','6');
+}
+
+static int has_fpu(void)
+{
+	u16 fcw = -1, fsw = -1;
+	u32 cr0;
+
+	asm("movl %%cr0,%0" : "=r" (cr0));
+	if (cr0 & (X86_CR0_EM|X86_CR0_TS)) {
+		cr0 &= ~(X86_CR0_EM|X86_CR0_TS);
+		asm volatile("movl %0,%%cr0" : : "r" (cr0));
+	}
+
+	asm("fninit ; fnstsw %0 ; fnstcw %1" : "+m" (fsw), "+m" (fcw));
+
+	return fsw == 0 && (fcw & 0x103f) == 0x003f;
+}
+
+static int has_eflag(u32 mask)
+{
+	u32 f0, f1;
+
+	asm("pushfl ; "
+	    "pushfl ; "
+	    "popl %0 ; "
+	    "movl %0,%1 ; "
+	    "xorl %2,%1 ; "
+	    "pushl %1 ; "
+	    "popfl ; "
+	    "pushfl ; "
+	    "popl %1 ; "
+	    "popfl"
+	    : "=r" (f0), "=r" (f1)
+	    : "g" (mask));
+
+	return !!((f0^f1) & mask);
+}
+
+static void get_flags(void)
+{
+	u32 max_intel_level, max_amd_level;
+	u32 tfms;
+
+	if (has_fpu())
+		set_bit(X86_FEATURE_FPU, cpu.flags);
+
+	if (has_eflag(X86_EFLAGS_ID)) {
+		asm("cpuid"
+		    : "=a" (max_intel_level),
+		      "=b" (cpu_vendor[0]),
+		      "=d" (cpu_vendor[1]),
+		      "=c" (cpu_vendor[2])
+		    : "a" (0));
+
+		if (max_intel_level >= 0x00000001 &&
+		    max_intel_level <= 0x0000ffff) {
+			asm("cpuid"
+			    : "=a" (tfms),
+			      "=c" (cpu.flags[4]),
+			      "=d" (cpu.flags[0])
+			    : "a" (0x00000001)
+			    : "ebx");
+			cpu.level = (tfms >> 8) & 15;
+			cpu.model = (tfms >> 4) & 15;
+			if (cpu.level >= 6)
+				cpu.model += ((tfms >> 16) & 0xf) << 4;
+		}
+
+		asm("cpuid"
+		    : "=a" (max_amd_level)
+		    : "a" (0x80000000)
+		    : "ebx", "ecx", "edx");
+
+		if (max_amd_level >= 0x80000001 &&
+		    max_amd_level <= 0x8000ffff) {
+			u32 eax = 0x80000001;
+			asm("cpuid"
+			    : "+a" (eax),
+			      "=c" (cpu.flags[6]),
+			      "=d" (cpu.flags[1])
+			    : : "ebx");
+		}
+	}
+}
+
+/* Returns a bitmask of which words we have error bits in */
+static int check_flags(void)
+{
+	u32 err;
+	int i;
+
+	err = 0;
+	for (i = 0; i < NCAPINTS; i++) {
+		err_flags[i] = req_flags[i] & ~cpu.flags[i];
+		if (err_flags[i])
+			err |= 1 << i;
+	}
+
+	return err;
+}
+
+/*
+ * Returns -1 on error.
+ *
+ * *cpu_level is set to the current CPU level; *req_level to the required
+ * level.  x86-64 is considered level 64 for this purpose.
+ *
+ * *err_flags_ptr is set to the flags error array if there are flags missing.
+ */
+int check_cpu(int *cpu_level_ptr, int *req_level_ptr, u32 **err_flags_ptr)
+{
+	int err;
+
+	memset(&cpu.flags, 0, sizeof cpu.flags);
+	cpu.level = 3;
+
+	if (has_eflag(X86_EFLAGS_AC))
+		cpu.level = 4;
+
+	get_flags();
+	err = check_flags();
+
+	if (test_bit(X86_FEATURE_LM, cpu.flags))
+		cpu.level = 64;
+
+	if (err == 0x01 &&
+	    !(err_flags[0] &
+	      ~((1 << X86_FEATURE_XMM)|(1 << X86_FEATURE_XMM2))) &&
+	    is_amd()) {
+		/* If this is an AMD and we're only missing SSE+SSE2, try to
+		   turn them on */
+
+		u32 ecx = MSR_K7_HWCR;
+		u32 eax, edx;
+
+		asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
+		eax &= ~(1 << 15);
+		asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));
+
+		get_flags();	/* Make sure it really did something */
+		err = check_flags();
+	} else if (err == 0x01 &&
+		   !(err_flags[0] & ~(1 << X86_FEATURE_CX8)) &&
+		   is_centaur() && cpu.model >= 6) {
+		/* If this is a VIA C3, we might have to enable CX8
+		   explicitly */
+
+		u32 ecx = MSR_VIA_FCR;
+		u32 eax, edx;
+
+		asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
+		eax |= (1<<1)|(1<<7);
+		asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));
+
+		set_bit(X86_FEATURE_CX8, cpu.flags);
+		err = check_flags();
+	} else if (err == 0x01 && is_transmeta()) {
+		/* Transmeta might have masked feature bits in word 0 */
+
+		u32 ecx = 0x80860004;
+		u32 eax, edx;
+		u32 level = 1;
+
+		asm("rdmsr" : "=a" (eax), "=d" (edx) : "c" (ecx));
+		asm("wrmsr" : : "a" (~0), "d" (edx), "c" (ecx));
+		asm("cpuid"
+		    : "+a" (level), "=d" (cpu.flags[0])
+		    : : "ecx", "ebx");
+		asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));
+
+		err = check_flags();
+	}
+
+	if (err_flags_ptr)
+		*err_flags_ptr = err ? err_flags : NULL;
+	if (cpu_level_ptr)
+		*cpu_level_ptr = cpu.level;
+	if (req_level_ptr)
+		*req_level_ptr = req_level;
+
+	return (cpu.level < req_level || err) ? -1 : 0;
+}