Received-SPF: pass (google.com: domain of linux-crypto-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
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,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-coco@lists.linux.dev, linux-mm@kvack.org,
        linux-crypto@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com,
        jroedel@suse.de, thomas.lendacky@amd.com, hpa@zytor.com,
        ardb@kernel.org, pbonzini@redhat.com, seanjc@google.com,
        vkuznets@redhat.com, jmattson@google.com, luto@kernel.org,
        dave.hansen@linux.intel.com, slp@redhat.com, pgonda@google.com,
        peterz@infradead.org, srinivas.pandruvada@linux.intel.com,
        rientjes@google.com, dovmurik@linux.ibm.com, tobin@ibm.com,
        vbabka@suse.cz, kirill@shutemov.name, ak@linux.intel.com,
        tony.luck@intel.com, marcorr@google.com,
        sathyanarayanan.kuppuswamy@linux.intel.com, alpergun@google.com,
        dgilbert@redhat.com, jarkko@kernel.org
Subject: Re: [PATCH Part2 v6 07/49] x86/sev: Invalid pages from direct map
 when adding it to RMP table
Message-ID: <Y63Jz01c7zLx03gQ@zn.tnic>
References: <cover.1655761627.git.ashish.kalra@amd.com>
 <243778c282cd55a554af9c11d2ecd3ff9ea6820f.1655761627.git.ashish.kalra@amd.com>
 <YuFvbm/Zck9Tr5pq@zn.tnic>
 <20221219150026.bltiyk72pmdc2ic3@amd.com>
 <Y6DEv4QuvIfwWlCW@zn.tnic>
 <ab96e918-c8b7-67d5-1dfd-320264858cec@amd.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <ab96e918-c8b7-67d5-1dfd-320264858cec@amd.com>
Precedence: bulk

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