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From: "H. Peter Anvin" <hpa@zytor.com>
To: Borislav Petkov <bp@alien8.de>
Cc: X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
	Borislav Petkov <bp@suse.de>
Subject: Re: [PATCH 3/4] x86, head_32: Remove second CPUID detection from default_entry
Date: Mon, 11 Feb 2013 07:49:14 -0800	[thread overview]
Message-ID: <18557aed-383a-4454-8222-3d2c0f0a78be@email.android.com> (raw)
In-Reply-To: <1360592538-10643-4-git-send-email-bp@alien8.de>

What about CPUs with inconsistent cpuid levels?  Yes, they can and do happen, as we discussed on IRC.

Borislav Petkov <bp@alien8.de> wrote:

>From: Borislav Petkov <bp@suse.de>
>
>We do that once earlier now and cache it into new_cpu_data.cpuid_level
>so no need for the EFLAGS.ID toggling dance anymore.
>
>Signed-off-by: Borislav Petkov <bp@suse.de>
>---
> arch/x86/kernel/head_32.S | 17 ++++-------------
> 1 file changed, 4 insertions(+), 13 deletions(-)
>
>diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
>index 73e084a6d2c5..e893ac09ca03 100644
>--- a/arch/x86/kernel/head_32.S
>+++ b/arch/x86/kernel/head_32.S
>@@ -410,18 +410,7 @@ default_entry:
> /*
>  * Check if it is 486
>  */
>-	movl $-1,X86_CPUID	# -1 for no CPUID initially
>-	movb $4,X86		# at least 486
>-	pushfl			# push EFLAGS
>-	popl %eax		# get EFLAGS
>-	movl %eax,%ecx		# save original EFLAGS
>-	xorl $0x200000,%eax	# flip ID bit in EFLAGS
>-	pushl %eax		# copy to EFLAGS
>-	popfl			# set EFLAGS
>-	pushfl			# get new EFLAGS
>-	popl %eax		# put it in eax
>-	xorl %ecx,%eax		# change in flags
>-	testl $0x200000,%eax	# check if ID bit changed
>+	cmpl $-1,X86_CPUID
> 	je is486
> 
> 	/* get vendor info */
>@@ -447,7 +436,9 @@ default_entry:
> 	movb %cl,X86_MASK
> 	movl %edx,X86_CAPABILITY
> 
>-is486:	movl $0x50022,%ecx	# set AM, WP, NE and MP
>+is486:
>+	movb $4,X86
>+	movl $0x50022,%ecx	# set AM, WP, NE and MP
> 	movl %cr0,%eax
> 	andl $0x80000011,%eax	# Save PG,PE,ET
> 	orl %ecx,%eax

-- 
Sent from my mobile phone. Please excuse brevity and lack of formatting.

  reply	other threads:[~2013-02-11 15:50 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-02-11 14:22 [PATCH 0/4 -v3] x86, head_32: Some cleanups Borislav Petkov
2013-02-11 14:22 ` [PATCH 1/4] x86, head_32: Remove i386 pieces Borislav Petkov
2013-02-13  0:07   ` [tip:x86/asm] " tip-bot for Borislav Petkov
2013-02-11 14:22 ` [PATCH 2/4] x86: Detect CPUID support early at boot Borislav Petkov
2013-02-13  0:09   ` [tip:x86/asm] " tip-bot for Borislav Petkov
2013-02-11 14:22 ` [PATCH 3/4] x86, head_32: Remove second CPUID detection from default_entry Borislav Petkov
2013-02-11 15:49   ` H. Peter Anvin [this message]
2013-02-11 17:15     ` Borislav Petkov
2013-02-11 17:21       ` H. Peter Anvin
2013-02-13  0:10   ` [tip:x86/asm] " tip-bot for Borislav Petkov
2013-02-11 14:22 ` [PATCH 4/4] x86, head_32: Give the 6 label a real name Borislav Petkov
2013-02-13  0:11   ` [tip:x86/asm] " tip-bot for Borislav Petkov
2013-02-11 16:56 ` [PATCH 0/4 -v3] x86, head_32: Some cleanups H. Peter Anvin

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