linux-kernel - Re: [PATCH 2/7] x86/enter: MACROS to set/clear IBRS

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Message-ID: <20180104221645.GC32035@hirez.programming.kicks-ass.net>
Date:   Thu, 4 Jan 2018 23:16:45 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/7] x86/enter: MACROS to set/clear IBRS

On Thu, Jan 04, 2018 at 09:56:43AM -0800, Tim Chen wrote:
> diff --git a/arch/x86/include/asm/spec_ctrl.h b/arch/x86/include/asm/spec_ctrl.h
> new file mode 100644
> index 0000000..16fc4f58
> --- /dev/null
> +++ b/arch/x86/include/asm/spec_ctrl.h

Does this really have to live outside of arch/x86/entry/ ?


> +.macro ENABLE_IBRS
> +	ALTERNATIVE "jmp 10f", "", X86_FEATURE_SPEC_CTRL
> +	PUSH_MSR_REGS
> +	WRMSR_ASM $MSR_IA32_SPEC_CTRL, $SPEC_CTRL_FEATURE_ENABLE_IBRS
> +	POP_MSR_REGS
> +10:
> +.endm
> +
> +.macro DISABLE_IBRS
> +	ALTERNATIVE "jmp 10f", "", X86_FEATURE_SPEC_CTRL
> +	PUSH_MSR_REGS
> +	WRMSR_ASM $MSR_IA32_SPEC_CTRL, $SPEC_CTRL_FEATURE_DISABLE_IBRS
> +	POP_MSR_REGS
> +10:
> +.endm
> +
> +.macro ENABLE_IBRS_CLOBBER
> +	ALTERNATIVE "jmp 10f", "", X86_FEATURE_SPEC_CTRL
> +	WRMSR_ASM $MSR_IA32_SPEC_CTRL, $SPEC_CTRL_FEATURE_ENABLE_IBRS
> +10:
> +.endm
> +
> +.macro DISABLE_IBRS_CLOBBER
> +	ALTERNATIVE "jmp 10f", "", X86_FEATURE_SPEC_CTRL
> +	WRMSR_ASM $MSR_IA32_SPEC_CTRL, $SPEC_CTRL_FEATURE_DISABLE_IBRS
> +10:
> +.endm
> +
> +.macro ENABLE_IBRS_SAVE_AND_CLOBBER save_reg:req
> +	ALTERNATIVE "jmp 10f", "", X86_FEATURE_SPEC_CTRL
> +	movl	$MSR_IA32_SPEC_CTRL, %ecx
> +	rdmsr
> +	movl	%eax, \save_reg
> +
> +	movl	$0, %edx
> +	movl	$SPEC_CTRL_FEATURE_ENABLE_IBRS, %eax
> +	wrmsr
> +10:
> +.endm
> +
> +.macro RESTORE_IBRS_CLOBBER save_reg:req
> +	ALTERNATIVE "jmp 10f", "", X86_FEATURE_SPEC_CTRL
> +	/* Set IBRS to the value saved in the save_reg */
> +	movl    $MSR_IA32_SPEC_CTRL, %ecx
> +        movl    $0, %edx

whitespace damage

> +	movl    \save_reg, %eax
> +	wrmsr
> +10:
> +.endm

Should not all those 10 things look like .Ldone_\@ or something ?