linux-kernel - Re: [tip:x86/mm] x86/mm: Add support for early encryption/decryption of memory

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Date:   Wed, 25 Oct 2017 10:34:57 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     arnd@...db.de, aryabinin@...tuozzo.com, dvyukov@...gle.com,
        mingo@...nel.org, pbonzini@...hat.com, peterz@...radead.org,
        torvalds@...ux-foundation.org, toshi.kani@....com,
        matt@...eblueprint.co.uk, corbet@....net, hpa@...or.com,
        konrad.wilk@...cle.com, dyoung@...hat.com, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, riel@...hat.com, bp@...e.de,
        lwoodman@...hat.com, glider@...gle.com, luto@...nel.org,
        mst@...hat.com, brijesh.singh@....com, thomas.lendacky@....com,
        rkrcmar@...hat.com, bp@...en8.de, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/mm] x86/mm: Add support for early encryption/decryption
 of memory

On 07/18/2017 03:51 AM, tip-bot for Tom Lendacky wrote:
> +/*
> + * This routine does not change the underlying encryption setting of the
> + * page(s) that map this memory. It assumes that eventually the memory is
> + * meant to be accessed as either encrypted or decrypted but the contents
> + * are currently not in the desired state.
> + *
> + * This routine follows the steps outlined in the AMD64 Architecture
> + * Programmer's Manual Volume 2, Section 7.10.8 Encrypt-in-Place.
> + */
> +static void __init __sme_early_enc_dec(resource_size_t paddr,
> +				       unsigned long size, bool enc)
> +{
> +	void *src, *dst;
> +	size_t len;
> +
> +	if (!sme_me_mask)
> +		return;
> +
> +	local_flush_tlb();
> +	wbinvd();

What is this TLB flush for?  WBINVD is mentioned in "Volume 2, Section
7.10.8", but TLB flushes are not.  Is it OK that this does not flush
global pages?