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.
next prev parent 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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