linux-kernel - Re: [PATCH V2] x86: use enum cpuid

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Message-ID: <20160121214732.GM21930@pd.tnic>
Date:	Thu, 21 Jan 2016 22:47:32 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Huaitong Han <huaitong.han@...el.com>, tglx@...utronix.de,
	mingo@...hat.com, david.vrabel@...rix.com, rusty@...tcorp.com.au,
	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] x86: use enum cpuid_leafs instead of magic numbers

On Thu, Jan 21, 2016 at 01:37:36PM -0800, H. Peter Anvin wrote:
> No, you still need to be able to find the beginning of the capability
> array, but the point is that right now it is implicit in that code that
> CPUID_1_EDX == 0.

Ah, you wanna be able to do:

---
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index af1112980dd4..143646f0add1 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -441,7 +443,7 @@ enable_paging:
 	movb %al,X86_MODEL
 	andb $0x0f,%cl		# mask mask revision
 	movb %cl,X86_MASK
-	movl %edx,X86_CAPABILITY
+	movl %edx,X86_CAPABILITY + CPUID_1_EDX*4
 
 is486:
 	movl $0x50022,%ecx	# set AM, WP, NE and MP

-- 
Regards/Gruss,
    Boris.

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