linux-kernel - Re: [PATCH] x86/mm: Remove unneeded TLB flush for in-place encryption

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Message-ID: <20171102115319.itui72sn76ajuf6e@pd.tnic>
Date:   Thu, 2 Nov 2017 12:53:19 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86/mm: Remove unneeded TLB flush for in-place encryption

On Wed, Nov 01, 2017 at 11:54:26AM -0500, Tom Lendacky wrote:
> A TLB flush is not required when doing in-place encryption or decryption
> since the area's pagetable attributes are not being altered.  To avoid
> confusion between what the routine is doing and what is documented in
> the AMD APM, delete the local_flush_tlb() call.
> 
> Suggested-by: Dave Hansen <dave.hansen@...el.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
>  arch/x86/mm/mem_encrypt.c |    1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index 16c5f37..53680a9 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -63,7 +63,6 @@ static void __init __sme_early_enc_dec(resource_size_t paddr,
>  	if (!sme_me_mask)
>  		return;
>  
> -	local_flush_tlb();
>  	wbinvd();
>  
>  	/*

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

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