From: Borislav Petkov <bp@alien8.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Borislav Petkov <bp@suse.de>
Subject: [PATCH 2/4] x86: Detect CPUID support early at boot
Date: Sun, 3 Feb 2013 17:14:37 +0100 [thread overview]
Message-ID: <1359908079-10469-3-git-send-email-bp@alien8.de> (raw)
In-Reply-To: <1359908079-10469-1-git-send-email-bp@alien8.de>
From: Borislav Petkov <bp@suse.de>
We detect CPUID function support on the boot CPU and save it for later
use, obviating the need to play the toggle EFLAGS.ID game every time. C
code is looking at ->cpuid_level anyway.
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/head_32.S | 36 +++++++++++++++++++++++++++++-------
1 file changed, 29 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index a9c5cc851285..ce6b557017f4 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -29,16 +29,16 @@
/*
* References to members of the new_cpu_data structure.
*/
-
#define X86 new_cpu_data+CPUINFO_x86
#define X86_VENDOR new_cpu_data+CPUINFO_x86_vendor
#define X86_MODEL new_cpu_data+CPUINFO_x86_model
#define X86_MASK new_cpu_data+CPUINFO_x86_mask
#define X86_HARD_MATH new_cpu_data+CPUINFO_hard_math
-#define X86_CPUID new_cpu_data+CPUINFO_cpuid_level
#define X86_CAPABILITY new_cpu_data+CPUINFO_x86_capability
#define X86_VENDOR_ID new_cpu_data+CPUINFO_x86_vendor_id
+#define X86_CPUID boot_cpu_data+CPUINFO_cpuid_level
+
/*
* This is how much memory in addition to the memory covered up to
* and including _end we need mapped initially.
@@ -263,6 +263,33 @@ subarch_entries:
num_subarch_entries = (. - subarch_entries) / 4
.previous
#else
+
+/*
+ * Initialize EFLAGS. Some BIOS's leave bits like NT set. This would confuse the
+ * debugger if this code is traced.
+ */
+ pushl $0
+ popfl
+
+/*
+ * Check whether this CPU supports CPUID, and, if so, save the highest standard
+ * CPUID function number for later.
+ */
+ movl $X86_EFLAGS_ID,%ecx /* EFLAGS.ID */
+ pushl %ecx
+ popfl /* set EFLAGS=ID */
+ pushfl /* get EFLAGS */
+ popl %eax
+ xorl %ecx,%eax
+ jnz 1f /* hw disallowed setting of ID bit */
+
+ xorl %eax,%eax
+ cpuid
+ movl %eax,pa(X86_CPUID) /* save largest std CPUID function */
+ jmp default_entry
+
+1:
+ movl $-1,pa(X86_CPUID)
jmp default_entry
#endif /* CONFIG_PARAVIRT */
@@ -377,11 +404,6 @@ default_entry:
/* Shift the stack pointer to a virtual address */
addl $__PAGE_OFFSET, %esp
-/*
- * Initialize eflags. Some BIOS's leave bits like NT set. This would
- * confuse the debugger if this code is traced.
- * XXX - best to initialize before switching to protected mode.
- */
pushl $0
popfl
--
1.8.1.2.422.g08c0e7f
next prev parent reply other threads:[~2013-02-03 16:15 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-03 16:14 [PATCH 0/4] x86, head_32: Some cleanups Borislav Petkov
2013-02-03 16:14 ` [PATCH 1/4] x86, head_32: Remove i386 pieces Borislav Petkov
2013-02-03 16:14 ` Borislav Petkov [this message]
2013-02-03 16:14 ` [PATCH 3/4] x86, head_32: Remove CPUID detection from default_entry Borislav Petkov
2013-02-03 16:14 ` [PATCH 4/4] x86, 32-bit: Drop new_cpu_data Borislav Petkov
2013-02-03 23:44 ` H. Peter Anvin
2013-02-04 5:27 ` Borislav Petkov
2013-02-04 5:44 ` H. Peter Anvin
2013-02-04 9:02 ` Borislav Petkov
2013-02-04 16:55 ` H. Peter Anvin
2013-02-04 17:01 ` Borislav Petkov
2013-02-11 14:22 [PATCH 0/4 -v3] x86, head_32: Some cleanups Borislav Petkov
2013-02-11 14:22 ` [PATCH 2/4] x86: Detect CPUID support early at boot Borislav Petkov
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