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Date: Thu, 29 Dec 2022 18:09:35 +0100
From: Borislav Petkov <bp@alien8.de>
To: "Kalra, Ashish" <ashish.kalra@amd.com>
Cc: Michael Roth <michael.roth@amd.com>, x86@kernel.org,
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Subject: Re: [PATCH Part2 v6 07/49] x86/sev: Invalid pages from direct map
 when adding it to RMP table
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In-Reply-To: <ab96e918-c8b7-67d5-1dfd-320264858cec@amd.com>

On Tue, Dec 27, 2022 at 03:49:39PM -0600, Kalra, Ashish wrote:
> Milan onward,

And before ML there's no SNP, right?

> there is H/W support for coherency between mappings of the
> same physical page with different encryption keys, so AFAIK, there should be
> no need to flush during page state transitions, where we invoke these direct
> map interface functions for re-mapping/invalidating pages.

Yah, that rings a bell.

In any case, the fact that flushing is not needed should be stated
somewhere in text so that it is clear why.

> I don't know if there is any other reason to flush after modifying
> the direct map ?

There's

        /*
         * No need to flush, when we did not set any of the caching
         * attributes:
         */
        cache = !!pgprot2cachemode(mask_set);


Does the above HW cover this case too?

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette