linux-kernel - Re: [PATCH v2] RFC: clear 1G pages with streaming stores on x86

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Message-ID: <20180730162926.GD11890@nazgul.tnic>
Date:   Mon, 30 Jul 2018 18:29:27 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Cannon Matthews <cannonmatthews@...gle.com>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andres Lagar-Cavilla <andreslc@...gle.com>,
        Salman Qazi <sqazi@...gle.com>, Paul Turner <pjt@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Peter Feiner <pfeiner@...gle.com>,
        Alain Trinh <nullptr@...gle.com>
Subject: Re: [PATCH v2] RFC: clear 1G pages with streaming stores on x86

On Tue, Jul 24, 2018 at 07:37:28PM -0700, Cannon Matthews wrote:
> diff --git a/arch/x86/lib/clear_page_64.S b/arch/x86/lib/clear_page_64.S
> index 88acd349911b..81a39804ac72 100644
> --- a/arch/x86/lib/clear_page_64.S
> +++ b/arch/x86/lib/clear_page_64.S
> @@ -49,3 +49,23 @@ ENTRY(clear_page_erms)
>  	ret
>  ENDPROC(clear_page_erms)
>  EXPORT_SYMBOL_GPL(clear_page_erms)
> +
> +/*
> + * Zero memory using non temporal stores, bypassing the cache.
> + * Requires an `sfence` (wmb()) afterwards.
> + * %rdi - destination.
> + * %rsi - page size. Must be 64 bit aligned.
> +*/
> +ENTRY(__clear_page_nt)
> +	leaq	(%rdi,%rsi), %rdx
> +	xorl	%eax, %eax
> +	.p2align 4,,10
> +	.p2align 3
> +.L2:
> +	movnti	%rax, (%rdi)
> +	addq	$8, %rdi
> +	cmpq	%rdx, %rdi
> +	jne	.L2
> +	ret
> +ENDPROC(__clear_page_nt)
> +EXPORT_SYMBOL(__clear_page_nt)

EXPORT_SYMBOL_GPL like the other functions in that file.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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