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Subject[PATCH] x86 boot time check for cpu features
This patch allows the real mode setup code to check for required
features (such as cmov, pae, etc.) that would normally just cause the
boot process to silently hang. Tested with a K6-2 (no cmov) and an
Athlon (has cmov), needs testing on a CPU without cpuid.

--

Brian Gerstdiff -ur linux-2.4.0t10/arch/i386/boot/setup.S linux/arch/i386/boot/setup.S
--- linux-2.4.0t10/arch/i386/boot/setup.S Tue Oct 31 17:06:34 2000
+++ linux/arch/i386/boot/setup.S Thu Nov 2 21:04:01 2000
@@ -364,6 +364,55 @@
xorw %bx, %bx
int $0x16

+/* This is butt ugly, but it works. */
+#ifdef CONFIG_X86_CMOV
+# define REQD_CMOV 0x00008000
+#else
+# define REQD_CMOV 0
+#endif
+#ifdef CONFIG_X86_PAE
+# define REQD_PAE 0x00000040
+#else
+# define REQD_PAE 0
+#endif
+#define REQD_FLAGS REQD_CMOV|REQD_PAE
+
+#if REQD_FLAGS
+/*
+ * We must check this here while we can still get a message to the console
+ * because instructions for newer processors (ie. cmovcc) may be present
+ * in C code.
+ */
+ pushfl
+ popl %eax
+ xorl $0x200000, %eax # check ID flag
+ pushl %eax
+ popfl
+ pushfl
+ popl %edx
+ xorl %edx, %eax
+ testl $0x200000, %eax
+ jnz cpuid_fail
+ xorl %eax, %eax
+ cpuid
+ cmpl $1, %eax
+ jb cpuid_fail
+ movl $1, %eax
+ cpuid
+ andl $REQD_FLAGS, %edx
+ cmpl $REQD_FLAGS, %edx
+ je cpuid_pass
+cpuid_fail:
+ pushw %cs
+ popw %ds
+ lea cpuid_fail_msg, %si
+ call prtstr
+1: jmp 1b
+cpuid_fail_msg:
+ .string "Required CPU features are not present - compile kernel for the proper CPU type."
+cpuid_pass:
+#endif
+
# Check for video adapter and its parameters and allow the
# user to browse video modes.
call video # NOTE: we need %ds pointing
diff -ur linux-2.4.0t10/arch/i386/config.in linux/arch/i386/config.in
--- linux-2.4.0t10/arch/i386/config.in Tue Oct 31 17:06:34 2000
+++ linux/arch/i386/config.in Thu Nov 2 18:53:59 2000
@@ -82,6 +82,7 @@
define_bool CONFIG_X86_GOOD_APIC y
define_bool CONFIG_X86_PGE y
define_bool CONFIG_X86_USE_PPRO_CHECKSUM y
+ define_bool CONFIG_X86_CMOV y
fi
if [ "$CONFIG_M686FXSR" = "y" ]; then
define_int CONFIG_X86_L1_CACHE_SHIFT 5
@@ -91,6 +92,7 @@
define_bool CONFIG_X86_USE_PPRO_CHECKSUM y
define_bool CONFIG_X86_FXSR y
define_bool CONFIG_X86_XMM y
+ define_bool CONFIG_X86_CMOV y
fi
if [ "$CONFIG_MK6" = "y" ]; then
define_int CONFIG_X86_L1_CACHE_SHIFT 5
@@ -105,6 +107,7 @@
define_bool CONFIG_X86_USE_3DNOW y
define_bool CONFIG_X86_PGE y
define_bool CONFIG_X86_USE_PPRO_CHECKSUM y
+ define_bool CONFIG_X86_CMOV y
fi
if [ "$CONFIG_MCRUSOE" = "y" ]; then
define_int CONFIG_X86_L1_CACHE_SHIFT 5
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